Testing the starter motor, to see if it's good or bad isn't difficult. In this tutorial, I'll explain the three tests you can perform to find out if it's kicked the bucket.
All three tests can be done with the starter motor still in the your pickup (no need to remove it to bench test it).
NOTE: The starter motor test in this tutorial is an on-car test. The photos I'm using show the starter motor off of the vehicle only to explain the test connections better.
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 4.6L Ford F150: 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010.
- 5.4L Ford F250 Light Duty: 1997, 1998, 1999, 2000.
- 5.4L Ford F250 Super Duty: 1997, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010.
- 5.4L Ford F350 Super Duty: 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010.
E-Series Vans: You can find the starter motor test for the E-Series vans here:
- How To Test The Starter Motor (1997-2014 4.6L, 5.4L V8 Ford E150, E250, E350) (at: troubleshootmyvehicle.com).
Crown Victoria And Grand Marquis: You can find the starter motor test for the Crown Vic/Grand Marquis here:
- How To Test The Starter Motor (1995-2011 4.6L Crown Victoria, Grand Marquis) (at: troubleshootmyvehicle.com).
Important Testing Tips
TIP 1 -Charge Battery: Ensure your battery is fully charged. A weak or dead battery can mimic starter motor issues and also skew the results of your test.
TIP 2 -Clean Battery Posts: Clean and remove corrosion from the battery cable terminals and battery posts. Any corrosion between the terminals and battery posts can hinder current flow to the starter motor, affecting it's ability to crank the engine and the results of your test.
TIP 3 -Use Jack Stands: Use jack stands to support the car, not just the jack. Be alert and think safety all of the time.
TIP 4 -Wear Safety Glasses: Wear safety glasses when working under the vehicle. Be alert and think safety all of the time.
TIP 5 -Keep Hands And Tools Clear Of Moving Parts: Be aware of belts, pulleys, and fans that are spinning as the engine is cranked (to perform the starter motor test). Keep your hands and tools away from these moving parts to avoid injury.
TIP 6 -Remove The Key: Remove the key from the ignition switch. This will prevent the engine from starting, in case the starter motor is OK.
Symptoms Of A Bad Starter Motor
As you're already aware, the starter motor's job is to crank the engine when you turn the key. This cranks the engine at a high speed, allowing it to start.
If the starter malfunctions, it can't properly crank the engine, leading to starting problems. In my experience, I've noticed that the starter motor usually malfunctions in one of two main ways:
- Engine no-crank problem: With a completely failed starter, the engine won't crank at all when you try to start the engine. It's probably the most common end-result of a bad starter motor.
- Intermittent engine no-crank problem: In this situation, the starter works most of the time, allowing the engine to crank and start normally. But every now and then, it fails and you experience the same "no-crank" issue as a complete failure. This can be frustrating because it's unpredictable and might not happen every time you try to start the engine.
NOTE: The starter needs to be checked or tested specifically when the no-cranking issue occurs. This is important because if you test the starter when it's working properly, it'll pass the test even though there's an underlying problem that causes the intermittent failure. By testing it during the no-crank situation, you're more likely to identify the starter as the culprit.
Tools Needed To Test The Starter Motor
No expensive diagnostic equipment is required to test the starter motor. Here's a list of the things you'll need:
- A jack.
- You'll need to raise your vehicle to access to the starter motor.
- Jack stands.
- A remote starter switch.
- If you'd like to see what a remote starter switch looks like, you can follow this link: Actron CP7853 Remote Starter Switch For 6V And 12V Automotive Starting Systems.
- You can either buy this tool online, or you can buy it at your local auto parts store (AutoZone, O'Reilly Auto Parts, etc.).
- A multimeter or a 12 Volt automotive test light.
- If you don't have a multimeter or need to upgrade yours, check out my recommendation here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
- A wire piercing probe.
- This tool isn't an 'absolute must-have tool,' but I can tell you from experience that it makes it a whole lot easier to probe the S terminal wire for the Start Signal.
- If you'd like to see what this tool looks like, you can find out more about it here: Wire Piercing Probe Tool Review (Power Probe PWPPPPP01).
- A helper.
TEST 1: Applying 12 Volts To The S Terminal
When you turn the key in your car, the ignition switch sends a 12 Volt electrical signal to the starter motor. This 12 Volt signal goes to a specific terminal on the starter motor called the solenoid S terminal. When the solenoid receives this 12 Volt signal, it engages the starter motor and cranks the engine.
For our first test, we're gonna bypass the ignition switch and apply 12 Volts directly to the solenoid S terminal. By bypassing the ignition switch, you're essentially testing if the starter motor itself is functional or not.
If applying 12 Volts directly to the S terminal cranks the engine, the starter motor is good. In this case, the problem likely lies somewhere in the ignition switch or wiring leading up to the solenoid, not the starter itself.
NOTE: Using a remote starter switch to apply 12 Volts to the starter motor solenoid is the safest and easiest way to accomplish this test section. Take all necessary safety precautions when working around a cranking engine.
You can see an example of a remote start switch and where to buy it here:
IMPORTANT: Remove the key from the ignition switch for this test. If your Ford pickup is equipped with a standard transmission, place it in neutral.
OK, let's get testing:
- 1
Raise the front of your vehicle and place it on jack stands (to gain access to the starter motor).
- 2
Disconnect the battery negative (-) terminal.
You'll reconnect it back in one of the following steps; for now, it's a safety precaution as you set up the test. - 3
Attach one end of the remote starter switch to the battery positive (+) post.
- 4
Attach the other end of the remote starter switch to the S terminal of the starter motor solenoid.
This is easier said than done, so take your time and make sure the connection is on the S terminal of the starter motor solenoid.
Also, in case you're wondering, you can leave the starter motor solenoid's S terminal wire connected to the engine's wiring harness connector or not, the test will work either way. - 5
Reconnect the battery negative (-) cable to the battery negative post.
- 6
Apply 12 Volts to the S terminal wire of the starter motor starter solenoid with your remote starter switch.
- 7
You'll get one of two results:
1.) The starter will activate and will turn over the engine.
2.) The starter motor won't do a thing.
Let's see what your test results mean:
CASE 1: The starter motor cranked the engine. This is the correct and expected test result and confirms the starter motor itself is functioning correctly.
Since the starter motor isn't cranking the engine when you turn the key to crank it, the next step is checking it's receiving an activation signal. Go to: TEST 2: Verifying The 12 Volt Start Signal.
CASE 2: The starter motor DID NOT crank the engine. This test result usually tells you that the starter motor is bad and needs replacement.
Before replacing the starter motor, your next step is ensuring that the cable connecting the starter motor to the battery positive (+) terminal is OK. Go to: TEST 3: Voltage Drop Testing The Battery Cable.
