It's not that difficult to test if the starter motor to find out if it's good or bad. In this tutorial, I'll show you the three tests you can perform on it to determine its condition and all without removing it from the vehicle.
By the way, the tests I'm gonna explain are all on-car tests. The photos show the starter motor off the vehicle only to explain the test connections.
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 4.6L Ford Crown Victoria: 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011.
- 4.6L Mercury Grand Marquis: 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011.
F-Series Pickups: You can find the starter motor test for the F-Series pickups here:
- How To Test The Starter Motor (1997-2010 4.6L, 5.4L Ford F150, F250, F350) (at: easyautodiagnostics.com).
E-Series Vans: You can find the starter motor test for the E-Series vans here:
Important Testing Tips
TIP 1 -Charge Battery: Ensure the battery is fully charged. A dead battery will cause the starter motor to not crank the engine. Not only that, a fully charged battery is needed to get an accurate starter motor test result.
TIP 2 -Clean Battery Posts: Clean and remove any corrosion from the battery terminals. This can stop the starter motor from getting the power it needs. Just like a dead battery, corrosion on the battery terminals can also affect the accuracy of your starter motor 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
In a nutshell, when you turn the key to start the engine in your car, the starter motor cranks the engine at a high speed. It's this cranking of the engine that allows it to start.
When the starter motor fails, it'll usually cause one of two headaches:
- Engine no-crank problem: The most common result of a bad starter motor is the engine failing to crank at all when you try to start the car (engine no-crank problem).
- Intermittent engine no-crank problem: Another sign can be an intermittent engine no-crank problem. This means the starter works most of the time but fails to crank the engine when you least expect it. This type of failure is probably one of the most frustrating because it's unpredictable.
NOTE: If you suspect a starter motor problem, it's important to have it checked or tested specifically when the no-cranking issue is happening. Testing the starter motor when it's working normally will not detect the problem, even though there is an underlying issue causing the intermittent failure.
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 your car key, the ignition switch sends a 12 Volt signal to the starter motor's solenoid S terminal. This signal activates the solenoid, which in turn engages the starter motor to crank the engine.
For our first test, we'll bypass the ignition switch and directly apply 12 Volts to the solenoid's S terminal. This test will help us determine right from the get-go if the starter motor is working properly.
If the engine cranks when you apply 12 Volts directly to the S terminal, the starter motor is functioning correctly. In this case, the issue is likely within the ignition switch or the wiring leading to the solenoid, rather than the starter motor 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.