1.9L Ford Escort Index Of Articles

• By: Abraham Torres-Arredondo
• Created: 11 September 2025
• Updated: 11 September 2025
• Articl Id: 10

The fuel pump pressure can be easily tested to diagnose a good or bad fuel pump on the 1991-1996 1.9L Ford Escort or Mercury Tracer.

What makes checking the fuel pump pressure so easy is the fact that the fuel injector rail has a fuel pressure test port, Schrader valve, where we can connect our fuel pressure test gauge to.

In this tutorial, I'll explain how to do the fuel pump pressure test to see if the fuel pump is behind an engine no-start problem or an engine performance problem.

I'm also going to show you how you can do a starting fluid test to see if an engine no-start problem is due to a fuel delivery problem.

APPLIES TO: This tutorial applies to the following vehicles:

• 1.9L Ford Escort: 1991, 1992, 1993, 1994, 1995, 1996.
• 1.9L Mercury Tracer: 1991, 1992, 1993, 1994, 1995, 1996.

IMPORTANT: Gasoline is highly flammable! Take all necessary safety precautions, be alert, be careful. Starting fluid and gasoline can ignite very easily.

Symptoms Of A Bad Fuel Pump

Your Ford Escort or Mercury Tracer's fuel pumps will usually let you down in one of two ways:

1. Total failure: The pump quits completely, fuel pressure drops to zero, and the engine simply won't start.
2. Weak pump: The pump is still running but can't keep up with demand. It's delivering just enough fuel to get the engine started, but not enough to keep it running the way it should.

When you're dealing with a weak pump that can't keep up, you'll usually be spotting one or more of these telltale performance problems:

• The engine takes a long time to start.
• The engine may start but will stall soon after.
• Lean air/fuel mixture diagnostic trouble codes illuminate the check engine light.
• The engine stalls as soon as you accelerate the engine under load.
• Backfire through the intake manifold when accelerating the engine under load.
• Lack of power when accelerating the engine under load.

Where To Buy A Fuel Pressure Gauge

When it comes to checking an engine no-start or an engine performance problem, a pressure gauge is one of the handiest tools you can own.

The good news is they're not expensive (like in the old days). Most auto parts stores carry them, and if you're looking to save a few bucks, you can find one online for even less. These are the ones I recommend:

Fuel Pressure Specifications

The fuel pressure specifications on the 1991-1996 1.9L Ford Escort or Mercury Tracer are:

Year	KOEO	KOER
1991-1993	35-45 PSI	30-40 PSI
1994-1995	35-45 PSI	28-33 PSI
1996-1998	38-46 PSI	31-38 PSI

• KOEO: Key On Engine OFF.
• KOER: Key On Engine Running.

TEST 1: Fuel Pressure Test With Gauge

Like I mentioned at the start of this tutorial, testing the fuel pump is a breeze because a fuel pressure test port (Schrader valve) is installed on the fuel rail. (see image 2 of 2 above).

This Schrader valve looks just like the one used on a bicycle tire, where you hook up the air pump to inflate the tire.

Before you begin the test, I want to point out that you should first make sure the fuel pump inertia switch hasn't tripped. If it has, the fuel pump won't get any power, and your fuel pressure test will only give you a 0 PSI reading. For more info, take a look at this section: Checking The Fuel Pump Inertia Switch.

OK, let's get started with this test:

1. 1

   Place a shop towel under the Schrader valve. The shop towel's job is to absorb any fuel that may leak when doing step 2.

2. 2

   Install the Ford Schrader valve adapter on the Schrader valve.

3. 3

   Connect the fuel pressure gauge to the Schrader valve adapter.

4. 4

   When ready, ask your helper to cycle the key on and off but don't crank the engine while checking for fuel leaks.
   
   If no fuel leaks, go to next step.
   
   If fuel is leaking, resolve the leak before continuing to the next step.

5. 5

   Have your helper to crank the engine while you observe the fuel pressure tester's gauge.

6. 6

   Your fuel pressure gauge will register one of the two following results:
   
   1.) The fuel pressure gauge will register the indicated fuel pressure specification (see: Fuel Pressure Specifications).
   
   2.) The fuel pressure gauge will NOT register the indicated fuel pressure specification.

Let's interpret your fuel pressure test result:

CASE 1: Gauge reading stays at 0 PSI. This result is telling you the fuel system isn't delivering anything to the fuel injector rail. In other words, the no-start you're troubleshooting is being caused by a total lack of fuel pressure.

This test result usually indicates the fuel pump is toast, but before you condemn the fuel pump as bad, you've got to make sure that it's actually getting power.

On the Ford Escort (Mercury Tracer) this is a piece of cake and this tutorial will help you with that:

• Power To Fuel Pump Check (1991-1996 1.9L Ford Escort, Mercury Tracer).

On the 1991-1995 Ford Escort and Mercury Tracer, it's a bit more complicated. What you'll need to do is locate the fuel pump fuse and make sure it's not blown. You may also need to check the fuel pump relay before concluding that the fuel pump is toast.

CASE 2: The fuel pressure gauge registered the correct fuel pressure specification. This fuel pressure gauge result lets you know that the fuel pump is working and delivering enough fuel to the fuel injectors.

If your 1.9L Ford Escort (Mercury Tracer) is not starting, it's due to another reason. However, the fuel pump is OK.

TEST 2: Using Starting Fluid

The starting fluid test is one of those old-school tricks that's been in the diagnostic toolbox forever. In fact, it was one of the very first checks I was taught when I started turning wrenches.

This test is especially useful when you don't have a fuel pressure gauge handy. It's not the most precise way to judge fuel pump performance, but it can quickly steer your no-start troubleshooting in the right direction.

One thing you need to keep in mind: this test only works if every spark plug wire is delivering spark. If you haven't verified that yet, make sure all four are sparking before you go spraying starting fluid into the intake.

These are the test steps:

1. 1

   Remove the intake air duct from the throttle body. You don't have to completely remove it, since you'll have to reconnect it in one of the next steps.

2. 2

   Open the throttle, manually, and spray starting fluid down the bore.

3. 3

   When you have sprayed a good squirt of starting fluid, quickly reconnect the air duct to the throttle body (you don't have to tighten the hose clamp).
   
   IMPORTANT: Reconnecting the intake air duct is a very important safety precaution in case you get a back-fire thru' the intake manifold.

4. 4

   Have your assistant crank the engine once the intake air duct is back on the throttle body.

5. 5

   You'll get one of two results with this test:
   
   1.) The engine will start momentarily and after a few seconds will die.
   
   2.) The engine will only crank but not start at all.

OK, let's find out what your results mean:

CASE 1: Engine started and ran briefly on starting fluid. That's your clue the no-start issue is tied to fuel delivery.

Nine times out of ten, it means the pump has given up. Still, if it were me, I'd back that up by hooking up a fuel pressure gauge before calling the fuel pump bad.

CASE 2: Engine didn't start with starting fluid. That's telling you the problem isn't fuel-related.

In other words, something else is causing the engine to not start, because fuel delivery isn't what's keeping the engine from running.

Just keep in mind: the starting fluid test only tells the truth if you've confirmed all four spark plug wires are sparking. Skip the spark check and the start fluid test results may have you chasing ghosts.

Checking The Fuel Pump Inertia Switch

Your 1.9L Ford Escort (or Mercury Tracer) is equipped with a fuel pump inertia switch. Its job is simple: cut the fuel pump circuit in the event of an impact so the pump shuts down instantly.

When that switch is tripped, you'll either have an engine that stalls out while driving or cranks but won't restart because the pump has no power feed. It's designed to trigger during a serious collision, but I've seen plenty of cases where a minor jolt or bump was enough to set it off.

That's why, before you start blaming the pump or diving into fuel pressure tests, it pays to check the inertia switch first.

On the 1991-1996 1.9L Ford Escort and Mercury Tracer, the fuel pump inertia switch is always on the right-hand (passenger side) rear area of the vehicle. The exact location depends on the body style:

• 3-door and 5-door hatchbacks: Mounted in the right side of the cargo area, just above the wheel well, behind the trim panel.
• 4-door sedans: Located in the right side of the luggage compartment (trunk).
• Wagons: Positioned in the right rear corner of the cargo area, directly behind the wheel well.

Resetting it is straightforward. Press the button on top of the switch until it bottoms out. If it had been tripped, you'll feel a solid click as the button locks back into place —and that restores power to the pump.

More 1.9L Ford Escort And Mercury Tracer Diagnostic Tutorials

You can find a complete list of 1.9L Ford Escort and Mercury Tracer tutorials in this index:

• 1.9L Ford Escort Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test The MAF Sensor (1991-1995 1.9L Ford Escort, Mercury Tracer).
• Common Causes Of Spark Plug Failure (1991-1995 1.9L Ford Escort, Mercury Tracer).
• How To Test For A Blown Head Gasket (1991-1995 1.9L Ford Escort, Mercury Tracer).
• How To Test Engine Compression (1991-1995 1.9L Ford Escort, Mercury Tracer).

• By: Abraham Torres-Arredondo
• Created: 11 September 2025
• Updated: 11 September 2025
• Articl Id: 9

The mass airflow (MAF) sensor on the 1991-1995 1.9L Ford Escort (or Mercury Tracer) can be tested easily with just a multimeter —you don't need a scan tool or any other expensive diagnostic equipment for this job.

In this tutorial, I'll walk you step by step through the four multimeter tests you can do to find out if the MAF sensor is good or bad.

You'll check the MAF signal voltage, verify it's receiving VPWR power, and confirm both Grounds (PWR GND and MAF RTN) are present.

APPLIES TO: This tutorial applies to the following vehicles:

• 1.9L Ford Escort: 1991, 1992, 1993, 1994, 1995.
• 1.9L Mercury Tracer: 1991, 1992, 1993, 1994, 1995.

Common Symptoms Of A Bad Ford MAF Sensor

Your Ford Escort or Mercury Tracer's fuel injection computer (PCM) needs to know how much air is entering the engine to calculate the correct fuel injection. And you guessed it —the MAF sensor is the one tasked with measuring that airflow.

When the MAF sensor fails, you'll usually see the check engine light illuminated along with one or more of these symptoms:

• On the 1991-1995 OBD I vehicles, you'll see one of the following codes:
  • Code 157: MAF Sensor Circuit Below Minimum Voltage.
  • Code 158: MAF Sensor Circuit Above Maximum Voltage.
  • Code 159: MAF Higher Or Lower Than Expected.
• On the 1996 OBD II vehicles, you'll see one of the following codes:
  • P0102: MAF Signal Low Input To PCM.
  • P0103: MAF Signal High Input To PCM.
• MAF sensor malfunction that DOES NOT light up the check engine light (CEL).
• Lean and/or Rich code(s).
• Fuel trim code(s).
• A tremendous lack of power upon acceleration.
• Black smoke coming from the tail-pipe.
• Bad gas mileage.
• Vehicle may idle rough and stall.

Circuit Descriptions Of The Ford MAF Sensor's Connector

The MAF sensor on your Ford Escort or Mercury Tracer uses a 4-wire connector. The table below identifies each circuit and its role, information you'll need for the diagnostic checks ahead.

Pin	Wire	Description
A	White with red stripe wire (WHT/RED)	VPWR –12 Volts Input in RUN or START
B	Black with dark green stripe (BLK/DK GRN)	PWR GND –Chassis Ground Input
C	Green with yellow stripe (GRN/YEL)	MAF RTN –MAF sensor Ground (provided by PCM)
D	Brown with black stripe (BRN/BLK)	MAF –MAF signal

IMPORTANT: All of the tests are ON CAR TESTS, do not remove the mass airflow sensor from the vehicle or from its plumbing.

TEST 1: Testing The MAF Signal

Your first step in testing the MAF sensor is to tap into the brown with black stripe (BRN/BLK) wire —which carries the MAF signal— with your multimeter, and monitor how it responds to engine airflow.

Here's what you should see during this MAF signal test:

• When you rev the engine and airflow increases, the MAF signal voltage should climb right along with it.
• When you let off the throttle and the RPMs drop, the MAF signal voltage should drop as airflow decreases.

No matter how many times you rev the engine and let off the throttle, the MAF signal voltage should climb as RPM goes up and drop back down as the engine settles to its base idle speed.

If the MAF sensor on your Ford Escort or Mercury Tracer is toast, the signal voltage will stay stuck at one reading —no matter how much you rev the engine up or down.

NOTE: The MAF sensor needs to stay connected to its wiring harness while you test it. That means you'll need a wire-piercing probe to tap into the MAF signal wire. If you don't already have one, here's the one I use and recommend: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).

These are the test steps:

1. 1

   Switch your multimeter to Volts DC.

2. 2

   Connect the black lead of the multimeter to the battery negative (-) terminal.

3. 3

   Connect the red lead to the brown with black stripe (BRN/BLK) wire using a wire-piercing probe.

4. 4

   Start the engine and let it idle.
   
   Once idle smooths out, note the voltage reading on the multimeter. A little fluctuation is normal. This first reading is your base MAF signal voltage.

5. 5

   Rev the engine by opening the throttle.
   
   You can do this at the throttle body by moving the linkage, or by having a helper step on the accelerator pedal.

6. 6

   The MAF signal voltage should rise as RPM increases.

7. 7

   Release the throttle to let the RPM come back down.

8. 8

   The voltage should drop as the RPMs fall.

9. 9

   Repeat the accelerate/release cycle a few times to verify the results are consistent.

Time to interpret your test result:

CASE 1: The signal voltage rises and falls as you open and close the throttle. This tells you the MAF sensor is operating correctly.

If the MAF sensor were faulty, the voltage would stay fixed at one value regardless of engine RPM.

CASE 2: The signal voltage does NOT respond to throttle movement. This usually means the MAF sensor is toast. It could also mean the MAF sensor isn't receiving power or Ground.

Before calling the MAF sensor defective, we need to confirm its getting power and then Ground. For the first of these test, go to: TEST 2: Making Sure The MAF Is Getting VPWR.

TEST 2: Making Sure The MAF Is Getting VPWR

The hot-wires on your Escort or Tracer's MAF sensor require a steady 12 Volt supply to operate. Without this VPWR feed, the hot-wires can't heat up and the PCM won't receive an usable signal.

For our next step, we're gonna confirm this VPWR power supply is available at female terminal A of the MAF sensor's 4-wire connector with your multimeter.

With key ON engine OFF (KOEO), you should see 10-12 Volts DC at terminal A. Anything lower, or no voltage at all, points to a VPWR power supply problem that must be fixed (and not a bad MAF sensor).

Alright, these are the test steps:

1. 1

   Disconnect the MAF sensor from its engine wiring harness connector.

2. 2

   Put your multimeter in Volts DC mode.

3. 3

   Connect the black multimeter lead to the battery negative (-) terminal.

4. 4

   Gently probe round female terminal A with the red multimeter lead.
   
   NOTE: Confirm that terminal A connects to the white with red stripe (WHT/RED) wire on the MAF sensor's 4-wire connector.

5. 5

   Turn the key to the RUN position, but don't crank or start the engine.

6. 6

   The multimeter should display 10 to 12 Volts.

Let's take a look at what your test result means:

CASE 1: The multimeter shows 10-12 Volts. This confirms the VPWR feed is present and working.

With power verified, the next step is to confirm the sensor has a solid chassis Ground at terminal B in: TEST 2: Making Sure The MAF Is Getting PWR GND (Chassis Ground).

CASE 2: The multimeter shows no voltage or less than 10 Volts. That means the sensor isn't being powered. A MAF without VPWR can't heat its wires and can't generate a viable MAF signal.

This result points directly to a VPWR power supply fault. Your next step is to diagnose why the VPWR feed is missing and repair the circuit so the sensor can come online.

TEST 3: Making Sure The MAF Is Getting PWR GND (Chassis Ground)

With VPWR confirmed, the next step is to verify the MAF has a reliable chassis Ground path. Without it (even if the VPWR feed is present), the hot-wire circuit inside the sensor is dead.

Ford designates this chassis Ground as PWR GND. Unlike the VPWR supply, it isn't switched —in other words, it's present at all times, whether the key is in OFF, RUN, or START position.

To test the PWR GND circuit, we'll connect our multimeter to terminal B (which connects to the black with dark green (BLK/DK GRN) wire of the connector).

Alright, here's what we need to do:

1. 1

   Unplug the MAF sensor from its engine wiring harness connector.

2. 2

   Set your multimeter to Volts DC.

3. 3

   Connect the red multimeter lead to the battery positive (+) terminal.

4. 4

   Probe female terminal B with the black multimeter test lead.
   
   NOTE: Check that terminal B corresponds to the BLK/DK GRN wire at the MAF sensor's 4-wire connector.

5. 5

   Your multimeter should show between 10 and 12 Volts.
   
   NOTE: Because this is a chassis Ground, it will always be present, whether the key is ON or OFF.

Let's take a look at what your test result means:

CASE 1: The multimeter shows 10-12 Volts. This confirms the sensor has a good chassis Ground.

With the PWR GND circuit checked, the next step is to check the second Ground circuit —the MAF RTN supplied by the PCM. Continue to: TEST 4: Making Sure The MAF Is Getting MAF RTN Ground.

CASE 2: The multimeter shows no voltage. That points directly to a missing chassis Ground. Without it, the sensor's hot-wires can't operate.

Your next move is to troubleshoot the PWR GND supply wire to find why this chassis Ground is missing and restore it so the circuit can function.

TEST 4: Making Sure The MAF Is Getting MAF RTN Ground

Here's what your test results are telling you so far:

• In TEST 1, the signal voltage did not react to changes in airflow.
• In TEST 2, you verified the sensor is receiving VPWR power.
• In TEST 3, you confirmed a solid chassis Ground (PWR GND).

Your final diagnostic test is to verify the PCM is supplying the MAF RTN Ground to the MAF sensor at terminal C.

Terminal C connects to the green with yellow stripe (GRN/YEL) wire (which connects directly to your Escort or Tracer's fuel injection computer).

NOTE: This Ground originates inside the fuel injection computer (PCM). Never apply battery voltage to this circuit —doing so will deep-fry the PCM instantly. The multimeter test I'm outlining below is a safe method for confirming the MAF RTN Ground at terminal C.

Let's get started:

1. 1

   Disconnect the MAF sensor from its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

   Connect the red multimeter test lead to the battery positive (+) terminal.

4. 4

   Probe female terminal C with the black multimeter test lead.
   
   NOTE: Check that terminal C actually corresponds to the GRN/YEL wire of the MAF sensor connector.

5. 5

   Turn the key to the RUN position but don't crank or start the engine.

6. 6

   You should see 10 to 12 Volts on the multimeter.

Let's take a look at what your test result means:

CASE 1: Multimeter shows 10-12 Volts. This test result confirms the PCM is supplying the MAF RTN Ground.

If you've reached this point and every other check has passed, the sensor is defective and needs replacement. Just to be clear, this conclusion is correct only if all of the following are true:

• TEST 1 →The MAF signal did not react (stayed stuck in one value) regardless of engine airflow (RPM).
• TEST 2 →The RED wire delivers 10–12 Volts (VPWR feed).
• TEST 3 →The BLK wire provides a solid chassis Ground (PWR GND).
• And in this step → The PCM supplies the MAF RTN Ground through terminal C.

CASE 2: Multimeter shows no voltage. This points directly to a missing PCM-supplied Ground. Without the MAF RTN Ground, the MAF sensor can't function.

Your next troubleshooting step is to see why this MAF RTN Ground is missing and repair the circuit so the sensor can function.

More 1.9L Ford Escort And Mercury Tracer Diagnostic Tutorials

You can find a complete list of 1.9L Ford Escort and Mercury Tracer tutorials in this index:

• 1.9L Ford Escort Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test The Fuel Pump (1991-1996 1.9L Ford Escort, Mercury Tracer).
• Common Causes Of Spark Plug Failure (1991-1995 1.9L Ford Escort, Mercury Tracer).
• How To Test For A Blown Head Gasket (1991-1995 1.9L Ford Escort, Mercury Tracer).
• How To Test Engine Compression (1991-1995 1.9L Ford Escort, Mercury Tracer).

• By: Abraham Torres-Arredondo
• Created: 11 September 2025
• Updated: 11 September 2025
• Articl Id: 8

Spark plugs may be small ignition components, but they play a critical role in keeping your Ford Escort or Mercury Tracer running smooth every time you start the engine.

When one or more spark plugs begin to wear or fail, engine performance issues will show up right away: cylinder misfires, rough idle, and a noticeable drop in performance.

When one or more spark plugs wear out or fail, you'll notice problems right away: misfires, rough idle, and loss of performance.

In this guide, I'll walk you through the common reasons spark plugs fail and how you can tell it's time to swap them out.

APPLIES TO: This tutorial applies to the following vehicles:

• 1.9L SOHC (P) Ford Escort: 1997, 1998, 1999, 2000, 2001, 2002.
• 1.9L DOHC (3) Ford Escort ZX-2: 1997, 1998, 1999, 2000, 2001, 2002.
• 1.9L SOHC Mercury Tracer: 1997, 1998, 1999.

What Causes Spark Plugs To Wear Out?

Every time you crank and start the engine, the spark plugs take a hit. The spark that jumps from the center to the side electrode slowly wears them down. It doesn't happen overnight, but it does every time the engine runs.

If you're using regular copper spark plugs, they typically last around 50,000 to 60,000 miles. Platinum-tipped spark plugs hold up much longer —close to 100,000 miles before you need to replace them.

Now, on a high-mileage engine, it's not just the normal wear and tear of daily driving wearing the them out. The leading cause of premature spark plug failure is carbon fouling.

This condition develops once the engine starts burning oil. The oil enters the combustion chamber and leaves heavy carbon deposits on the spark plug electrodes.

When carbon bridges the gap between the electrodes, the spark can no longer jump across. The result is a dead cylinder, which shows up as a misfire and a rough idle.

On the 1996 Escort/Tracer with OBD II, carbon-fouled plugs will usually trigger the PCM to flag the bad cylinder. You'll get a check engine light and a stored misfire code —usually P0300 to P0304.

When Should I Replace The Spark Plugs?

Deciding when to replace the spark plugs comes down to two key factors:

1. The replacement interval specified in the owner's manual.
2. The actual condition of the engine —especially if it has started burning oil.

The service interval in the owner's manual is based on ideal operating conditions: a healthy engine, no oil consumption, and the correct type of plug installed (copper or platinum). If the engine meets those conditions, the factory schedule is a reliable guideline.

However, once the engine starts burning oil, carbon fouling takes out the spark plugs much sooner —often before normal electrode wear shows up. In that case, you may be replacing them every few months just to keep it running smooth.

If your Escort or Tracer's engine is burning oil and the plugs are carbon-fouled to the point they no longer fire, you'll know it's time to replace them when you notice:

• Rough idle at low RPM (such as when you're stopped at a traffic light).
• The check engine light on, with a misfire code stored in the PCM's memory.

If you're not sure whether your Escort or Tracer's engine is burning oil, here are the telltale signs:

• You're regularly adding engine oil just to keep the dipstick at the full mark.
• You've got blue smoke coming out from the tailpipe (especially when you step on the gas).
• You see blue smoke (out of the tailpipe) on startup, especially after your Escort (or Tracer) has been sitting for a while.

On the flip side, if the engine isn't burning oil, that's good news. In most cases, you'll get the full service life out of the spark plugs without premature fouling.

With copper spark plugs (the OEM type), expect to replace them at roughly 50,000 miles.

If you've installed platinum or iridium plugs, they'll last much longer —typically close to 100,000 miles before, you'll need to replace them.

Which Spark Plugs Should I Buy: Motorcraft Or Brand X?

From the factory, the 1.9L Ford Escort (or Mercury Tracer) came with Motorcraft copper spark plugs.

Since Motorcraft is the original equipment (OE) brand, using them at tune-up time guarantees you're installing the same type the engine was designed for.

That said, you're not limited to Motorcraft only. As long as the spark plugs you choose match the correct heat range and specifications for your 1.9L Escort or Tracer, any quality brand will perform properly.

Here's the part you'll want to be paying close attention to:

• If the engine is burning oil, there's no benefit in paying extra for premium plugs. Go with low-cost copper plugs, since carbon fouling will short out any type once oil starts coating the electrodes. Brand name doesn't matter here either —you'll be replacing them frequently either way.
• If the engine is not burning oil, upgrading to platinum plugs makes sense. They offer longer service life and more consistent performance. Any quality brand will do the job —sticking with Motorcraft is an option if you prefer OE, but it's not required.

Other Causes Of Spark Plug Failure

Like I've said before, when a spark plug fails to fire, the result is a cylinder misfire —no way around it.

From a diagnostic standpoint, the reasons a spark plug stops firing usually fall into two main categories:

1. Engine mechanical problems that end up fouling the spark plug with oil, fuel, or heavy carbon deposits.

Here are the key things to look for:

• Oil fouling from worn piston rings or leaking valve stem seals, allowing oil into the combustion chamber and onto the spark plug.
• A fuel injector stuck open, flooding its cylinder and leaving the plug wet with raw fuel.
• A bad spark plug wire not delivering spark to its spark plug.
• An bad ignition coil.
• Low compression in one or more cylinders, leading to incomplete combustion and eventual spark plug fouling.

2. Installation mistakes —these are the kinds of errors that physically damage a spark plug or prevent it from firing correctly.

The most common examples include:

• Over-tightening the spark plug, which can crack the ceramic insulator or damage the threads.
• Dropping the spark plug before installation and creating a hairline fracture in the insulator.
• Closing the spark plug gap accidentally while handling it, preventing the spark from jumping across the electrodes.
• Installing the spark plug with an incorrect gap setting.
• Washing the engine while it's still hot, causing thermal shock that cracks the spark plug's porcelain insulator —resulting in a misfire.

CASE STUDIES:

I've had the chance to diagnose and resolve quite a few cylinder misfires over the years (caused by installation errors). Here's a case study of one from a few years back:

• Diagnosing A Toyota Corolla Misfire Case Study (at: troubleshootmyvehicle.com).

Here's one that deals with low cylinder compression causing a cylinder misfire. This one I diagnosed on my brother-in-law's car:

• Troubleshooting A Hard To Diagnose Misfire Case Study (GM 3.1L, 3.4L) (at: troubleshootmyvehicle.com).

In this last case study, the spark plug and spark plug wire had carbon tracks causing a cylinder misfire:

• Carbon Tracks Are A Common Cause Of Ignition Misfires.

More 1.9L Ford Escort And Mercury Tracer Diagnostic Tutorials

You can find a complete list of 1.9L Ford Escort and Mercury Tracer tutorials in this index:

• 1.9L Ford Escort Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test The MAF Sensor (1991-1995 1.9L Ford Escort, Mercury Tracer).
• How To Test The Fuel Pump (1991-1996 1.9L Ford Escort, Mercury Tracer).
• How To Test For A Blown Head Gasket (1991-1995 1.9L Ford Escort, Mercury Tracer).
• How To Test Engine Compression (1991-1995 1.9L Ford Escort, Mercury Tracer).

• By: Abraham Torres-Arredondo
• Created: 11 September 2025
• Updated: 11 September 2025
• Articl Id: 7

Checking for a blown head gasket isn't complicated. In fact, you've got four different tests you can do to find out if the head gasket on your 1991-1996 1.9L Ford Escort or Mercury Tracer has failed.

In this tutorial, I walk you through all four. Two of them don't need any tools and only take a few minutes to do.

The other two involve a little more —one is a compression test with a compression tester, and the other is a block test with a combustion leak detector.

Hopefully you're not dealing with a blown head gasket. But if you are, one of these four tests will confirm it for you.

APPLIES TO: This tutorial applies to the following vehicles:

• 1.9L Ford Escort: 1991, 1992, 1993, 1994, 1995, 1996.
• 1.9L Mercury Tracer: 1991, 1992, 1993, 1994, 1995, 1996.

Symptoms Of A Blown Head Gasket

This isn't every single symptom a blown head gasket can throw at you, but these are the most common ones you're likely to run into when you diagnose one of these engines:

1. You start the engine and it overheats within minutes for no clear reason, even when the cooling system looks like it's working right.
2. You find engine oil mixed with coolant, causing it to turn into a milky-white color.
3. You see white smoking come out of the tailpipe (which is antifreeze burning inside the cylinders).
4. The engine cranks but refuses to start.
5. You've got no compression on two side-by-side cylinders.

TEST 1: Engine Oil Mixed With Coolant

The head gasket on your 1.9L Ford Escort or Mercury Tracer keeps three critical engine elements from crossing paths: the coolant, the engine oil, and the combustion pressures/gases inside the cylinders.

To break it down, the head gasket's job is to:

• Keep the coolant contained and flowing only through its passages in the block and cylinder head.
• Keep the engine oil in its own galleries and out of the cylinders where it doesn't belong.
• Keep the combustion pressure sealed tight inside each cylinder so you don't lose power.

When the engine overheats badly, the aluminum cylinder head warps or the gasket itself burns through, and that's when those three elements begin mixing together.

From what I've seen over the years, the most common result of a blown head gasket on a four-cylinder engine is the coolant mixing with the engine oil. When that happens, the oil turns a milky-white color, like coffee with too much creamer.

For our first head gasket diagnostic test, we'll check the color of the engine oil sticking to the engine oil dipstick.

These are the test steps:

1. 1

   Open the hood.

2. 2

   Pull out the engine oil dipstick.

3. 3

   Check the color of the oil sticking to the dipstick.

4. 4

   You'll see one of two things:
   
   1.) The color of the oil will be a milky white color (like coffee with too much creamer).
   
   2.) The color of the oil will be its normal color.

Now, let's see what your test result means:

CASE 1: The engine oil is a milky-white color (like coffee with too much creamer). This is a clear sign the head gasket on your 1.9L Ford Escort or Mercury Tracer has failed and that coolant is mixing with the engine oil in the crankcase.

CASE 2: You see the engine oil hold its normal old or dirty color. That's a good sign so far, but it doesn't mean you can rule out a blown head gasket just yet.

Your next head gasket test is: TEST 2: Coolant Shooting Out Of Radiator.

TEST 2: Coolant Shooting Out Of Radiator

So far, TEST 1 confirmed your Escort or Tracer's engine oil isn't mixing with coolant —since it hasn't turned a milky-white color.

Now, we'll check if the head gasket is still sealing the compression, combustion, and exhaust gases inside the cylinders the way it should.

We can do this easily by taking the cap off the radiator and seeing if coolant gets shot out of the radiator while cranking the engine.

If coolant does get shot out of the radiator neck (while cranking the engine), your Escort or Mercury's head gasket is blown.

IMPORTANT: Never do this test on a hot engine! Coolant under pressure can spray out and cause severe burns. Always make sure the engine is completely cold before you remove the radiator cap.

This is what you need to do:

1. 1

   Remove the radiator cap from the radiator.
   
   IMPORTANT: The engine should be completely cold before you open the radiator cap.

2. 2

   Check the coolant level.
   
   If the coolant level is low, top it off with water before going on to the next step.

3. 3

   Stand at a safe distance (from the engine) but within eye-view of the radiator.

4. 4

   Have your helper crank the engine.

5. 5

   You'll see one of two results:
   
   1.) The coolant shoots out when the engine was cranked.
   
   2.) The coolant was not disturbed at all.

Let's examine your test result:

CASE 1: The coolant shot out of the open radiator. This confirms the head gasket on your 1.9L Ford Escort or Mercury Tracer is blown.

CASE 2: The coolant stayed put (undisturbed) in the radiator. That's the test result you want to see, and so far things look good.

From here, what you do next depends on how the engine behaves:

• If the engine doesn't start, go to: TEST 3: Engine Compression Test.
• If the engine starts but runs hot, head over to: TEST 4: Using A Chemical Block Tester (Combustion Leak Tester).

TEST 3: Engine Compression Test

Over the years, I've run into more than a few vehicles with a blown head gasket that didn't show the usual signs. The engine oil wasn't mixed with coolant, and cranking the engine with the radiator cap off didn't send coolant shooting out either.

Even without those symptoms, the head gasket had blown and kept the engine from starting, and it was the compression test that ended up nailing what was really happening.

What happened in those cases was the gasket burned through between two side-by-side cylinders, causing them to lose their ability to compress the air/fuel mixture.

If you take a look at the photo of the head gasket at the beginning of this tutorial, it shows you exactly that kind of failure.

To check if the same thing has happened on your Ford Escort (or Mercury Tracer), we'll do an engine compression test in this test section.

NOTE: This tutorial explains how to do and interpret the compression test in more detail: How To Test Engine Compression (1991-1995 1.9L Ford Escort, Mercury Tracer).

Here's what you need to do:

1. 1

   Disable the fuel system by removing the fuel pump relay.

2. 2

   Disable the ignition system by disconnecting the ignition coil pack from its connector.

3. 3

   Disconnect the spark plug wires from the spark plugs. I strong recommend you use a spark plug wire puller for this (to avoid having the wire's metal terminal stay stuck on the spark plug).
   
   NOTE: Label the spark plug wires so that you can reconnect them back to the correct spark plug when you're done.

4. 4

   Remove the spark plugs.

5. 5

   Install the compression tester (hand tight only) on the first cylinder you're gonna test.

6. 6

   Have a helper crank the engine while you observe the compression tester.

7. 7

   Have your helper stop cranking the engine once the needle on the gauge stops climbing.

8. 8

   Write down the compression readings.

9. 9

   Repeat steps 5 through 8 on the remaining cylinders.

Let's take a look at your test results mean:

CASE 1: Two side-by-side cylinders show 0 PSI compression. The head gasket has failed and is letting those two cylinders' compression bleed into each other.

CASE 2: All cylinders hold good, solid compression. This is the correct and expected test result.

If you're troubleshooting an engine no-start problem, this result rules out the head gasket as the cause of the issue.

TEST 4: Using A Chemical Block Tester (Combustion Leak Tester)

I've run into cases where the vehicle had a head gasket issue, but its engine still started and ran, and didn't show any of the symptoms that the first three tests are designed to confirm.

In these particular cases, what happened instead was that the engine overheated within minutes of starting, and for no obvious reason.

When you run into this type of situation, the surest way to confirm or rule out a head gasket failure is to do a block test with a combustion leak detector.

Because of how effective it is, the block test is the standard test repair shops turn to when they have to confirm a blown head gasket with absolute certainty.

Here's how it works:

• You start by filling the tester with a special blue chemical (see photo above).
• Next, you place the tester assembly on the open radiator neck.
  • You may need to drain a little coolant first, since the tool needs to gulp some of the air sitting inside the radiator.
• With the tester in place, you start the engine.
• Now you squeeze the rubber bellow to pull the radiator's air up through the two fluid-filled chambers.
  • As the air bubbles up through the fluid, it causes a chemical reaction.
• If the blue chemical turns yellow (on a gasoline engine), that tells you combustion gases are entering the radiator. This confirms you're dealing with a blown head gasket, a cracked block, or a cracked cylinder head.
• If the blue chemical stays blue, then you can conclude you're not dealing with a blown head gasket, a cracked block, or a cracked cylinder head problem.

Where can you get the chemical and block tester? Here:

Frequently Asked Questions

1.) How can I tell if the cylinder head is cracked?

The only accurate way to do this is with the cylinder head removed from the engine block. At that point, you can either perform a visual inspection yourself or have the head pressure-tested.

If the crack is large, you'll usually spot it right away without special tools. But if nothing obvious shows up, a machine shop can pressure test the head to confirm or rule out a hidden crack.

2.) How can I verify if the cylinder head is warped?

Checking for warpage can only be done with the cylinder head removed from the block. Once it's off, the first step is to clean the head gasket surface completely.

Next, you need to place a precision straight-edge across the gasket surface and use feeler gauges to check for gaps. Any spot where the gauge slips under the straight-edge confirms the head isn't perfectly flat.

This method is the only accurate way to determine if the cylinder head is warped.

And if the engine overheated (which is usually what causes a blown head gasket), you can assume the head is warped. At that point, machining or resurfacing it at a machine shop isn't optional —it's required.

3.) Do I need to resurface the cylinder head?

Yes. Any time the head gasket has failed, the cylinder head should be sent to a machined shop to be checked (with a pressure test) and then resurfaced to make sure it seals properly when reinstalled.

Skipping this step risks another head gasket failure, especially if the engine has overheated.

More 1.9L Ford Escort And Mercury Tracer Diagnostic Tutorials

You can find a complete list of 1.9L Ford Escort and Mercury Tracer tutorials in this index:

• 1.9L Ford Escort Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test The MAF Sensor (1991-1995 1.9L Ford Escort, Mercury Tracer).
• How To Test The Fuel Pump (1991-1996 1.9L Ford Escort, Mercury Tracer).
• Common Causes Of Spark Plug Failure (1991-1995 1.9L Ford Escort, Mercury Tracer).
• How To Test Engine Compression (1991-1995 1.9L Ford Escort, Mercury Tracer).

• By: Abraham Torres-Arredondo
• Created: 11 September 2025
• Updated: 11 September 2025
• Articl Id: 6

One of the things that makes testing the engine compression on the 1.9L engine in your 1991-1996 Ford Escort or Mercury Tracer is that the spark plugs are pretty accessible and can be easily removed.

In this tutorial, I walk you through how to run the compression test —and just as important— how you interpret the results.

I'll also explain how to run a wet compression test to see if worn piston rings or valves are behind a low reading on one or more cylinders.

I've laid out every step in a clear, step-by-step sequence, so you can quickly pinpoint whether a low or 0 PSI compression issue is causing a cylinder misfire or an engine no-start problem.

APPLIES TO: This tutorial applies to the following vehicles:

• 1.9L Ford Escort: 1991, 1992, 1993, 1994, 1995, 1996.
• 1.9L Mercury Tracer: 1991, 1992, 1993, 1994, 1995, 1996.

Symptoms Of Low Or No Cylinder Compression

From my own experience, I can tell you that compression problems usually show up in one of two ways:

• Engine no-start condition: The engine cranks over but it doesn't fire up and start.
• Cylinder misfire or rough idle: Low compression causes the engine to misfire or idle rough, but as soon as you press the gas pedal, the problem disappears.

If the engine starts and runs but there's still a compression issue in one or more cylinders, you'll notice one or more of the following engine performance problems:

• Engine 'misses' at idle but 'miss' disappears as you accelerate.
• Rough idle that disappears when you accelerate.
• Cylinder misfire setting one or more of the following codes (1996 OBD II only):
  • P0300: Random Cylinder Misfire.
  • P0301: Cylinder #1 Misfire.
  • P0302: Cylinder #2 Misfire.
  • P0303: Cylinder #3 Misfire.
  • P0304: Cylinder #4 Misfire.
• Check engine light is illuminated with a MAP sensor trouble code (even tho' the MAP sensor is good).
• Blue smoke coming out of the tailpipe.
• Bad gas mileage.

With this info under our belts, let's head down to the next subheading and get testing.

Which Compression Tester Should I Buy?

There are lot of engine compression testers to choose from and many places to buy them. I'm gonna' make some recommendations to you:

TEST 1: Dry Compression Test

Alright, before you get started, let me pass along a few important suggestions that'll save you some headaches:

• Label each spark plug wire with the cylinder number it belongs to.
• Use spark plug wire pullers to disconnect the wires.
• Always remove the spark plugs from a cold or completely cooled-down engine.

If you just yank the spark plug wires off the plugs by hand, chances are one or more wires' metal terminal will separate from the wire and stay stuck on the spark plug. Yes, you can crimp that terminal back on, but it's a hassle you're better off avoiding in the first place (by using spark plug wire pullers).

If you don't have the spark plug wire puller, this is the one that I use and recommend: Performance Tool W80519 Adjustable Spark Plug Boot And Wire Remover (Amazon affiliate link).

About removing the spark plugs from a cold engine, this is important because if you remove the spark plugs from a hot engine, you risk stripping the spark plug hole threads in the cylinder head. Believe you me, this is a nightmare you definitely want to avoid.

OK, time to get your hands dirty:

1. 1

   Disable the ignition system by disconnecting the ignition coil from its electrical connector. This will prevent the ignition coil from sparking during the test.

2. 2

   Disable the fuel system by removing the fuel pump relay. Disabling the fuel system will prevent fuel from being injected into each cylinder when the test is performed.

3. 3

   Remove the spark plugs.
   
   NOTE: When removing the spark plugs, be careful not to drop any of them on the floor, or you run the risk of having the spark plugs porcelain insulator crack and then you'll have a misfire on your hands.

4. 4

   Thread the engine compression gauge into the spark plug hole for the #1 engine cylinder.
   
   NOTE: Hand tighten the compression gauge only! Do not use any type of tool to get it tight.

5. 5

   Have your helper crank the engine till the needle on the compression gauge stops climbing.

6. 6

   Record on paper the value at which the needle stopped and the number of the engine cylinder on a piece of paper.

7. 7

   Release the pressure on the gauge and repeat steps 5 and 6 one more time.

8. 8

   Check the compression of the remaining cylinders.

Let's take a look at what your test results mean:

CASE 1: You see 0 PSI on all four cylinders. That result tells you the engine has suffered one of the following conditions:

• A broken timing belt.
• A blown head gasket.
• A catastrophic internal engine failure.

Any reading that drops below 100 PSI (even if it isn't a flat 0) points to serious internal mechanical trouble.

CASE 2: The compression values from each cylinder show some variation. Up to a certain point, that can be considered normal.

If the variation stays within an acceptable range, the engine usually runs without any performance issues. Where you run into problems is when the values drift too far apart. The good thing is you can check whether the differences you wrote down point to an actual cylinder problem or not. For that explanation, head over to: Interpreting The Results Of The Engine Compression Test.

CASE 3: All four cylinders show very similar compression numbers. This is the result you hope to see.

When the compression values are close together, it confirms the engine's internals are in good shape. Since the engine is healthy, you can rule out a compression issue as the cause of the problem you're troubleshooting.

Interpreting The Results Of The Engine Compression Test

On any high-mileage engine, you can expect to see the compression numbers between cylinders vary a little bit, and that's normal. Where you start to run into real performance issues is when that variation gets too wide.

To put a number on it, you look for the lowest compression reading to stay within 15% of the highest reading you got. Once a cylinder drops below that margin, you've got a weak cylinder that will misfire.

The good news is you can confirm if that low reading is the cause of your problem by doing a quick calculation. It's nothing complicated —you can work it out with a pen and paper, or you can plug in your numbers into my online calculator here: Online Low Engine Compression Calculator. If you want to work it out yourself, here's the math:

• STEP 1: Take the highest compression reading and multiply it by 0.15 (15% in decimal form).
• STEP 2: Round the result to the nearest whole number (for example: 25.6 becomes 26).
• STEP 3: Subtract that number from your highest compression reading.
• ANSWER: The final number is the lowest compression value a cylinder can have before it's considered out of spec.

Here's an example to show you exactly how this works using real compression readings:

Cylinder	Pressure
#1	175 PSI
#2	170 PSI
#3	165 PSI
#4	120 PSI

Next, let's do a little math to find out the lowest acceptable reading:

• STEP 1: Multiply 175 by 0.15 = 26.25.
• STEP 2: Round 26.25 down to 26.
• STEP 3: Subtract 26 from 175 = 149.
• RESULT: 149 PSI is the lowest compression value this engine can be running with.

Since cylinder #4 comes up with only 120 PSI, this is the weak cylinder screwing things up and causing the misfire.

To confirm if your lowest number is within an acceptable limit, you'll do the same calculation again—only this time you plug in the highest reading from your own test instead of the sample values I used.

From here, the next step is to figure out why that cylinder's compression is low. Head over to: TEST 2: Wet Compression Test.

TEST 2: Wet Compression Test

Most of the time, when you see a cylinder with low or even 0 PSI, it's usually one of two things going on:

• The piston rings are worn and do not seal anymore.
• The cylinder head valves are worn or damaged and let compression escape.

The good news is you don't have to start tearing the engine apart to figure out which one it is. You can find out by doing a wet compression test.

This simply involves adding a little engine oil into the cylinder that showed the low (or 0) PSI, then run the compression test again. One of two things will happen:

• Compression shoots up: That tells you the piston rings in that cylinder are causing the issue.
• Compression stays flat (no change): That points to the intake or exhaust valves as the source of the problem.

Alright, let's get to it.

1. 1

   Add a tablespoon (or two) of engine oil in the cylinder you need to retest.
   
   I suggest using a small and long funnel so that the oil will reach the inside of the cylinder.

2. 2

   Once you've added the oil, install the compression gauge, and as before just hand tighten it.

3. 3

   Now, have your helper crank the engine till the needle stops climbing on the compression gauge.

4. 4

   You'll see one of two results:
   
   1.) The needle will climb higher than the previous compression number you recorded for this specific cylinder.
   
   2.) The needle will not move at all or stay at the same number you recorded earlier.
   
   Whatever value your compression tester reads, write it down again.

5. 5

   If you have another cylinder that needs to be tested, repeat steps 1 thru' 4 on it now.

Let's go over what your test results mean:

CASE 1: The compression reading climbed higher (in the low or 0 PSI cylinder). This tells you that the low number you saw in the dry compression test (TEST 1) is coming from worn piston rings.

The reason the reading jumps is because the motor oil you poured in is helping those rings seal tighter against the cylinder wall. You only get this kind of rise when piston ring wear is the culprit.

CASE 2: The compression reading DID NOT climb (it stayed the same). This tells you the low or 0 PSI result you saw earlier is being caused by intake or exhaust valves in the cylinder head that are worn or damaged and not sealing the way they should.

More 1.9L Ford Escort And Mercury Tracer Diagnostic Tutorials

You can find a complete list of 1.9L Ford Escort and Mercury Tracer tutorials in this index:

• 1.9L Ford Escort Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test The MAF Sensor (1991-1995 1.9L Ford Escort, Mercury Tracer).
• How To Test The Fuel Pump (1991-1996 1.9L Ford Escort, Mercury Tracer).
• Common Causes Of Spark Plug Failure (1991-1995 1.9L Ford Escort, Mercury Tracer).
• How To Test For A Blown Head Gasket (1991-1995 1.9L Ford Escort, Mercury Tracer).