Testing the starter motor on any GM 3.8L equipped car or mini-van (to find out if it's the one causing your car or mini-van not to crank) can be done in two easy tests and in this article, I'll show you how.
With the step by step test instruction in this article, you should be able to accomplish the starter motor test in under 30 minutes, using only a multimeter and a helper.
To see if this starter motor test tutorial covers your specific Chevy or Buick or Olds or Pontiac 3.8L equipped vehicle, you can take a look at the list of applications on the box labeled 'Applies To:' on the column on the right and scroll with the prev and next arrow buttons.
Contents of this tutorial:
Symptoms Of A Bad Starter Motor
The most common symptom of a bad starter are:
- Turn the key to crank the car (or mini-van) and the engine does not turn over (crank).
- A jump start does not help. The vehicle's engine still refuses to crank.
- The battery has been charged and/or replaced and still the vehicle does not crank.
- Turn the key to start the car (or mini-van) and all you hear is a small knock and nothing else.
Although the above list is a not a very complete list of symptoms, the theme that runs thru' them, and any other related symptom, is that the engine will not turn over when the key is turned to crank the vehicle.
NOTE: If you're troubleshooting an engine no-start (instead of an engine no-crank), see this tutorial:
STARTER TEST 1: Testing The Starter Solenoid 'S' Signal
Before you start testing, you need to make sure that the battery is fully charged. A low battery can make you think that the starter motor is bad when it really isn't.
Also, you need to remove the battery cable terminals from the battery and check for corrosion on them. If corroded, please clean and crank the car (or mini-van) to see if this solves the no-crank condition and/or before proceeding with the test.
Lastly, you'll need to access the starter motor from underneath your car or mini-van. So please take all necessary safety precautions, like using safety glasses, jack stands, etc.
OK, to get this show on the road, this is what you'll need to do:
- 1
Raise the front of your 3.8L equipped GM car or mini-van (using a jack) and place it on jack stands.
- 2
Grab and set your multimeter on Volts DC mode.
- 3
Probe the wire that attaches to the S terminal of the starter motor solenoid with the red multimeter test lead.
The easiest way to do this is using a tool like a wire piercing probe, to pierce this wire and then attach the multimeter test lead to it.
Which is the S terminal wire? This is the wire that connects with a nut to the smaller of the three studs on the starter solenoid. This S terminal wire (circuit) is the one that delivers the Start (Crank) signal from the ignition switch (the orange arrow points to this S terminal in the photo above). - 4
Ground the black multimeter test lead.
NOTE: I'm gonna' recommend that you use a battery jump start cable to Ground the multimeter's test lead directly on the battery negative (-) terminal. This way you can ensure that you're gonna' have a good path to Ground, since you may you may NOT be able to find a clean and rust-free spot on the bottom of the vehicle to Ground the multimeter's black test lead. - 5
When everything is set and ready, have your helper turn the key to crank the engine.
The starter motor won't crank the car, of course, but this is the only way to verify the presence of the Crank (Start) signal from the ignition switch. - 6
As your helper is cranking the engine, your multimeter will register one of two results:
1.) 10 to 12 Volts DC.
2.) 0 Volts DC.
OK, let's make sense of the readings that your multimeter recorded in the test:
CASE 1: Your multimeter registered 10 to 12 Volts. This is good, since it let's you know that the starter motor is getting a crank signal from the ignition switch.
This test result also confirms that the neutral safety switch is good and doing its job. Now, in the majority of the cases, you could stop testing here, replace the starter motor and be done. But, I suggest one more test so that you can be absolutely sure there isn't another issue to deal with.
TEST TIP: Although you have verified that the starter motor is getting the crank signal from the ignition switch, I suggest that you apply 12 Volts directly to the S terminal of the starter motor solenoid (with a jumper wire connected to the battery positive (+) terminal). STARTER TEST 2 I'll show you how to do it. Go to: STARTER TEST 2: Applying 12 V To The S Terminal.
CASE 2: If your multimeter DID NOT register 10 to 12 Volts. This result lets you know that the reason the starter motor is not cranking up the engine is through a lack of a Crank (Start) signal.
Here's why: Without the ignition switch's crank signal, the starter motor will not crank the engine. This signal could be missing because either the neutral safety switch is bad or because ignition switch itself is fried. Testing these two components is beyond the scope of this article but you have now eliminated the starter motor as bad.
I recommend one more test, and this is to apply 12 Volts to the starter solenoid's S terminal. Go to: STARTER TEST 2: Applying 12 V To The S Terminal.
STARTER TEST 2: Applying 12 V To The S Terminal
The next step, in troubleshooting the starter motor, is to apply 12 Volts directly to the S terminal of the starter motor solenoid (with a jumper wire connected to the battery positive (+) terminal).
You can also use a remote starter switch. If you need to see what one looks like, you can see it here: Innova 3630 Remote Starter Switch (Amazon affiliate link).
This is a very simple test, but you do have to take one very important precaution:
IMPORTANT: Remove the key from the ignition switch before starting this test. This will prevent the engine from starting, in case the starter motor is OK.
OK, this is what you'll need to do:
- 1
Disconnect the wire that attaches to the S terminal of the starter motor solenoid.
- 2
Using a jumper wire that's long enough, or a remote start switch, apply 12 Volts to the S terminal of the starter motor solenoid.
- 3
As you apply these 12 Volts (to the S terminal of the starter solenoid), 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 take a look at what your test results mean:
CASE 1: The starter motor cranked the engine. This means that the starter motor is good and that you have an electrical issue keeping the starter motor from cranking the engine.
Also, since the starter motor did come alive and cranked the engine, this result lets you know beyond a shadow of a doubt that the starter motor is good and that you need to look at the ignition switch, or neutral safety switch or Fusible Link as the cause of the no-start condition on your car or mini-van.
CASE 2: The starter motor DID NOT crank the engine. This usually means that your starter motor is bad and needs to be rebuilt or replaced.
I suggest one more test and this is to test the battery cable (that attaches to the starter motor solenoid) for corrosion. This can be accomplished very easily with a voltage drop test. Go to: STARTER TEST 3: Voltage Drop Testing The Battery Circuit.
STARTER TEST 3: Voltage Drop Testing The Battery Circuit
So far in your testing, you have verified that the battery is fully charged and in STARTER TEST 1 you confirmed that the starter motor is being supplied with the crank signal (when your helper turned the key to crank the car).
The next step is to make sure that the battery positive (+) cable that attaches to the starter motor's solenoid is supplying full battery voltage and Amperage to the starter motor.
If the starter motor isn't getting full battery current, usually due to hidden corrosion somewhere on the cable, the starter motor won't be able to crank the engine.
We can easily verify this by doing a simple voltage drop test.
These are the test steps:
- 1
Place your multimeter in Volts DC mode.
- 2
Attach the red multimeter test lead to the center of the bolt that attaches the positive (+) battery cable to the battery.
NOTE: The spot on this bolt, which the multimeter test lead will be touching, has to be clean and rust-free.
You may need two helpers for this test step, since someone will have to hold the red multimeter test lead onto the battery positive (+) terminal bolt and someone else inside the vehicle (to crank it when everything is set up). - 3
Now, at the starter motor solenoid, place the black multimeter test lead on the stud that connects to the positive (+) battery cable.
The orange arrow labeled BAT+ in the photo above points to this stud. Maintain the black multimeter test lead in this position throughout the next step. - 4
When everything is ready, have your helper crank the engine while you observe the multimeter.
Although the starter motor won't crank the engine, your helper has to turn the ignition switch to START the engine for the voltage drop test to work. - 5
If everything is OK (no voltage drop), the multimeter will register 0.5 Volts or less (0.5 V is really 0 Volts).
If there's a voltage drop problem in this wire, your multimeter will register some voltage, usually 5 Volts or above.
OK, now that the testing part is done, let's take a look at what your results mean:
CASE 1: Your multimeter indicated NO voltage drop (which is 0.5 Volts or less). This result indicates that the starter motor is receiving all of the battery voltage and amperage it needs to crank the vehicle.
This result also confirms that the starter motor is bad and needs to be replaced if you have:
- Confirmed that the ignition switch and the neutral safety switch are good and that the starter is getting the crank signal (STARTER TEST 1).
- Confirmed that the starter motor did not crank the engine when you applied 12 Volts to the S terminal of the starter motor solenoid (STARTER TEST 2).
- Confirmed that the starter is getting all of the power it would need to crank the engine (this test section).
Now, before you remove the starter motor, do two more things.
1.) Turn the engine manually (using a 1/2 ratchet and the appropriate socket). This will verify that the engine is not mechanically locked up.
2.) Bench test the starter motor. You can find the step-by-step instructions here: How To Bench Test A Starter Motor (Step By Step) (at: easyautodiagnostics.com).
CASE 2: Your multimeter registered 5 Volts or more. This result tells you that a voltage drop does exist and this voltage drop is not a good thing to have in this circuit.
The solution is to simply disconnect the positive (+) battery cable from the battery and thoroughly clean it. Also, the end of this very same cable, that's attached to the starter motor solenoid, should be disconnected, inspected and cleaned.
Cleaning the end that attaches to the starter motor solenoid should be done with a small piece of sand paper. Once both ends of the battery positive cable are clean, reconnect everything and try cranking the car. If the voltage drop was the cause of the no-crank condition, your vehicle will now crank and start.
Related Test Articles
I have written quite a few articles on the GM 3.8L equipped cars to help you solve the most common types of problems with specific troubleshooting tests. You can find the ones I've written for this site, by checking out the following index of articles:
Here's a sample of the tutorials you'll find:
- How To Do An Engine Compression Test (GM 3.8L).
- How To Test A Blown Head Gasket (GM 3.8L).
- How To Diagnose Misfire Codes P0300-P0306 (GM 3.8L).
- How To Test The Ignition Coil Packs (at: easyautodiagnostics.com).
- How To Test The Ignition Control Module (at: easyautodiagnostics.com).
- How To Test The MAF Sensor (at: easyautodiagnostics.com).
If this info saved the day, buy me a beer!
