PART 2: Checking The Fuel Injector Spray Pattern
If you've reached this section, you've checked the fuel injector's internal resistance and confirmed it's within the indicated specification.
Now that you've ruled out an internal electrical issue with the fuel injector, the next step is to remove it.
Once removed from the fuel injector rail, we're gonna check that it sprays properly using a DIY fuel injector cleaning tool (which you can buy online) and a can of brake cleaner.
This fuel injector cleaning tool kit includes two important components:
- A 12 Volt power module that triggers the fuel injector in pulses, similar to how the fuel injection computer does it.
- An adapter that connects the fuel injector to a spray can of brake cleaner.
After setting up the test, a good fuel injector should spray the brake cleaner in a fine mist. If the injector is clogged or faulty, it will either squirt the cleaner or not spray at all.
The cool thing about this fuel injector cleaner took kit is that it's not expensive. You can purchase it here:
- QX Fuel Injector Tester & Adapter for Diagnosis and Cleaning of Injectors DIY Cleaning Tool Kit (at: amazon.com).
- EM276SET Fuel Injector Tester & Adapter DIY Cleaning Tool Kit Set (at: amazon.com).
IMPORTANT: Before installing the same or new fuel injector back on the fuel injector rail, take a look at: Important Tips For Installing A Fuel Injector.
CAUTION: Use safety glasses when performing the fuel injector cleaning procedure.
Alright, these are the test steps:
- 1
Remove the fuel injector.
- 2
Connect the fuel injector to the plastic adapter.
NOTE: I've found that securing the fuel injector to the adapter with a thick rubber band helps to make the whole process easier and less messier. - 3
Connect the fuel injector to the tool's power module.
NOTE: Follow the tool's safety and recommended set-up instructions. - 4
Connect the cleaning kit's power module to your pickup's battery.
- 5
Connect the fuel injector/adapter to a spray can of brake cleaner and press them onto the spray can.
- 6
Activate the power module.
- 7
The fuel injector should spray fuel in a fine mist and in a conical shape.
Let's interpret your test result:
CASE 1: The fuel injector did not spray at all. This tells you that the fuel injector is bad and needs to be replaced.
CASE 2: The fuel injector sprayed the brake cleaner in a fine mist and in a conical pattern. This tells you that the fuel injector is OK.
CASE 3: The fuel injector sprayed the brake cleaner in a squirt or a stream (not in a fine mist). This tells you that the fuel injector is dirty/clogged.
Continue cleaning the fuel injector until it starts to spray in a fine mist. If the cleaning it doesn't restore the injector's spray pattern to that of a fine mist, you'll need to replace it.
Important Tips For Installing A Fuel Injector
When installing a fuel injector (whether it's a new one or the same one) on the fuel injector rail, it's important to follow these important tips:
- Use new fuel injector O-rings: Always replace the O-rings when installing a fuel injector, whether it's new or the same one. New injectors usually come with new O-rings, but if you're reinstalling the same injector, you'll need to buy them. New O-rings are critical to ensure a good seal and prevent gasoline and vacuum leaks.
- Lubricate the O-rings: Before placing the new O-rings onto the injector, coat them with a thin layer of clean engine oil (5W-30 or lighter). Don't use silicone-based greases or other lubricants.
Lubricating the O-rings with light engine oil helps avoid damaging them when inserting the fuel injector into both the injector rail and the intake manifold port. If installed without lubrication, they'll end up getting damaged and you'll have gasoline or vacuum leaks when you crank and start the engine. - Replace damaged connectors: If the fuel injector's connector is damaged, replace it with a new one. Ford fuel injector connectors are notorious for having their locking tab break when disconnecting them from the fuel injector. If the fuel injector connector is broken, replace it.
- Avoid butt connectors: Instead of using butt connectors to join the new connector's wires to the engine wiring harness, solder the wires for a permanent repair. Butt connectors are notorious for eventually losing their grip on the wires, causing false contact issues.
Remember, the goal is to prevent gasoline leaks and avoid the risk of fire. Take your time to ensure everything is properly seated and secure.
Precautions To Take When Removing The Intake Manifold Plenum
Before and during the intake manifold's plenum removal, keep the following important tips in mind:
- Have a repair manual on hand: Get a repair manual (preferably a Haynes Repair Manual, as Chilton manuals are less reliable) to learn (in detail) what the intake manifold removal process involves. The manual will also provide torque specifications for the bolts.
- Disconnect the battery: Disconnect the negative (-) battery cable before removing the intake manifold plenum and keep it disconnected throughout the fuel injector testing procedure.
- Prevent foreign objects from falling into the open intake manifold ports: Ensure that no foreign objects, such as bolts, nuts, or any metal parts, fall into the open manifold port runners. Once the plenum is removed, cover the open intake runners with a clean rag or rags to prevent anything from falling in.
- Organize removed parts: As you remove bolts, nuts, and other components from the intake plenum, place them in a container and keep them away from the engine compartment.
- Do not crank the engine: Never crank the engine with the plenum removed from the lower intake manifold.
Anything falls into the open intake runners, without you knowing, and the engine is started, you're gonna be in a big world of hurt! Since it may require the removal of the cylinder head to retrieve the part that fell in. So be alert and be careful.
Taking off the plenum isn't rocket science; lots of folks do it and don't have any problems. The key is to take some simple precautions to avoid any complications or issues.
More 4.2L Ford Diagnostic Tutorials
You can find a complete list of 4.2L Ford F150/F250 tutorials and wiring diagrams in this index:
Here's a small sample of the tutorials you'll find in the index:
- How To Test Engine Compression (4.2L Ford).
- How To Test The Throttle Position Sensor (4.2L Ford F150 And F250).
- How To Test The Ford EGR Valve EGR Vacuum Solenoid, DPFE Sensor.
- How To Test The Coil Pack (Ford 3.0L, 3.8L, 4.0L, 4.2L).
If this info saved the day, buy me a beer!
