You might think that the starter motor test is difficult to do, but nothing could be further from the truth! Not to mention, you don't need to remove the starter motor to test it.
In this tutorial, I'll show you how to tell if the starter is good or bad without needing expensive diagnostic equipment.
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:
- Important Testing Tips.
- Symptoms Of A Bad Starter Motor.
- Tools Needed To Test The Starter Motor.
- TEST 1: Applying 12 Volts To The 'S' Terminal.
- TEST 2: Verifying The 12 Volt Start Signal.
- TEST 3: Voltage Drop Testing The Battery (+) Cable.
- More 3.1L Buick Regal And Oldsmobile Cutlass Supreme Test Tutorials.
You can find this tutorial in Spanish here: Cómo Probar El Motor De Arranque (1989-1993 3.1L Buick Regal, Oldsmobile Cutlass Supreme) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 3.1L Buick Regal: 1989, 1990, 1991, 1992, 1993.
- 3.1L Oldsmobile Cutlass Supreme: 1993, 1994, 1995.
- 3.1L Oldsmobile Ciera: 1996.
WIRING DIAGRAM: You can find the starter motor wiring diagram here:
Important Testing Tips
As I mentioned at the beginning of the tutorial, testing the starter motor isn't difficult. However, you should keep the following testing suggestions in mind to avoid complications:
TIP 1: The battery must have a full charge before starting any of the tests in this tutorial.
TIP 2: The battery cable terminals and the battery posts should be clean and corrosion-free before starting the tests.
TIP 3: Read the entire article first to familiarize yourself with the tests.
TIP 4: Use jack stands for safety. Don't trust the jack alone to keep your vehicle up in the air while you're underneath it!
TIP 5: Take all necessary safety precautions. Use safety glasses while working underneath the vehicle. Be alert and think safety all of the time.
Symptoms Of A Bad Starter Motor
The starter's job is to crank the engine. If it fails, it stops cooperating and won't start the engine.
Unfortunately, two types of starter failures occur in the wild:
- The starter motor causes an engine no-crank problem.
- The starter motor causes an intermittent no-crank problem.
In most cases, the starter motor fails and stops cranking the engine until it's replaced. In the intermittent no-crank problems, the starter works well most of the time, but not now and then.
In general, these intermittent starter motor problems are the most difficult to diagnose. The key to successfully resolving an intermittent no-crank problem is to test the starter motor when it's not cranking the engine.
Tools Needed To Test The Starter Motor
You'll need a few basic tools to test the starter motor. Here's a list of what you'll need:
- Jack.
- You'll need to raise your vehicle to gain 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, Pepboys, 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 (at: easyautodiagnostics.com).
- A wire piercing probe.
- This tool is not 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 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 receives an activation signal on the S terminal of its solenoid. In the photo above, I've labeled the S terminal with the letter S.
Your first test is to apply the 12 Volts (from your vehicle's battery) to the S terminal of the starter solenoid.
I recommend you apply these 12 Volts with a tool called a remote starter switch. The following test instructions assume you're using one.
If the starter motor is OK, these 12 Volts will activate the starter motor and crank the engine.
If there's a problem with the starter motor or any of the circuits connected to it, it will not activate (and the engine will not crank).
IMPORTANT: Remove the key from the ignition switch for this test.
OK, let's get testing:
- 1
Raise the front of your vehicle and place on it 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.
