In this tutorial, I'm gonna explain the three tests you can perform on your 4.2L V6 equipped F150 to find out if the starter motor is good or bad.
All the test steps are explained in a step-by-step manner so you can easily and quickly determine if the starter motor has kicked the bucket. By the way, there's no need to remove the starter motor to 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:
- 4.2L V6 Ford F150: 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008.
- 4.2L V6 Ford F250 Light Duty: 1998.
Starting System Wiring Diagrams: The following wiring diagrams are available to help you further troubleshoot the starter motor:
- Starter Motor Circuit Wiring Diagram (1997-1998 4.2L V6 Ford F150, F250 Light Duty).
- Starter Motor Circuit Wiring Diagram (1999 4.2L V6 Ford F150).
- Starter Motor Circuit Wiring Diagram (2000-2003 4.2L V6 Ford F150).
Important Testing Tips
TIP 1 - Charge Battery: To get the most accurate test result from your starter motor test, the battery must be fully charged. If the battery is weak or dead, it'll mimic a starter motor issue and also skew the results of your test.
TIP 2 - Clean Battery Posts: Clean and remove any 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: If you do need to raise your pickup to access the starter motor -don't trust the jack alone to keep it up in the air. Jack stands are a must to support the vehicle while working underneath it. 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 already know, the starter motor's sole job is to turn the engine over fast enough to get it started when you turn the key to crank the engine.
Sooner or later, the starter motor is going to wear out, and when this happens, you're gonna see one of two types of malfunctions:
- Engine no-crank problem: When the starter motor has completely failed, the engine won't crank at all when you try to start it.
This means when you turn the key, you'll hear nothing or maybe just a click, but the engine won't turn over. This is the most common result of a bad starter motor. - Intermittent engine no-crank problem: In this case, the starter motor works most of the time, allowing the engine to crank and start normally. However, occasionally, the starter will fail, causing the same "no-crank" issue as a complete failure.
This is frustrating because it's unpredictable. One time the engine starts without a problem, and the next time, it won't crank at all. This intermittent failure makes it harder to diagnose and fix.
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
The cool thing about testing the starter motor is that you don't need any expensive testing or diagnostic equipment. You'll need a few things, though. Here's a list of items that'll help and make diagnosing the starter motor a whole lot easier and safer:
- 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
The starter motor gets a 12-Volt activation signal from the ignition switch when you turn it to crank and start the engine.
For our first starter motor test, we're gonna bypass the ignition switch and apply 12 Volts directly to the starter motor.
If the starter motor cranks the engine, we can conclude right off the bat that it's good and working correctly.
If it doesn't crank the engine, we'll continue with the next tests to further troubleshoot the problem.
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.
S Terminal ID: Look for the thinner wire among the two that connect to the starter solenoid. Follow this wire to the smaller threaded stud on the solenoid. This is your S terminal.
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.
