STARTER TEST 3: Voltage Drop Testing The Battery (+) Cable
Corrosion on the battery positive (+) post or battery positive cable can keep the starter motor from cranking the engine.
You've probably already cleaned the battery cable terminals and the battery posts but there's still a good chance that hidden corrosion (on the battery positive cable) is blocking battery power from reaching the starter motor (this condition is known as a voltage drop).
The absolute best way to eliminate this possibility, is with a simple multimeter voltage drop test of the battery positive cable (that attaches to the large stud of the starter motor solenoid).
To further explain what a voltage drop is: a voltage drop is simply a condition in which unseen corrosion blocks a lot of the battery power from reaching the starter motor. When this happens, the starter motor will not be able to crank the engine in your Chrysler 3.9L, 5.2L, 5.9L pickup (van or SUV) even though the battery is in a fully charged state.
OK, to get started, this is what you need to do:
Place your multimeter in Volts DC mode. Attach the red multimeter test lead to the center of the positive battery terminal. If the positive battery post isn't clean, clean a spot right on the top of it. It's important that the multimeter test lead make contact right in the center of the positive battery post.
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 and someone else will need to crank the vehicle while you perform the next step.
With the black multimeter test lead, touch the center of the starter solenoid stud to which the big battery cable attaches to. You'll maintain the black multimeter test lead in this position throughout the next step.
Now, have a helper turn the key to crank the engine from inside the vehicle. This is important, since a voltage drop test has to be done while the component in question is working (or trying to work).
OK, if all is good (no voltage drop), your multimeter will register 0 Volts (0.5 Volts is still 0 Volts). If there's a voltage drop, your multimeter will register voltage (usually above 7 Volts DC.)
OK, now that the testing part is done, let's take a look at what your results mean:
CASE 1: Your multimeter registered 0 Volts (no voltage drop). This result indicates that the starter motor is receiving all of the battery voltage and Amperage it needs to crank the vehicle.
This also means that the starter motor is bad, and here's why:
- In STARTER TEST 1 you confirmed that the starter motor doesn't work when you apply power to the S terminal wire of the starter motor solenoid.
- STARTER TEST 2 you confirmed that the starter motor is receiving the crank signal.
- In this test step you have confirmed that no voltage drop exists on the battery positive cable.
These 3 test results, taken together, indicate that the starter motor is bad. Replacing the starter motor should solve your 'no-crank' condition.
I'm going to make two more recommendations to you. 1.) Before removing the starter motor, manually turn the engine using a 1/2 ratchet and the appropriate socket on the crankshaft pulley. This is just to make sure the engine or the A/C Compressor have not locked up and causing the no-crank condition and 2.) Bench test the starter motor after removing it. This is a super easy test to do and you can find this article by clicking 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 is not a good result.
The good news is that this can easily be corrected, since a voltage drop is always caused by some sort of corrosion issue on the battery positive cable or terminals or the battery positive post.
The solution is to thoroughly clean the battery positive post and the battery positive (+) terminal (both the end that attaches to the battery positive post and the end the connects to the starter motor solenoid).
After cleaning, try cranking the engine. If it cranks and starts, no further testing is required.
Related Test Articles
You'll find a complete list of Chrysler 3.9L, 5.2L, 5.9L tutorials in the following index: Chrysler 3.9L, 5.2L, 5.9L Index Of Articles.
Here's a small sample of the articles/tutorials you'll find in the index:
- How To Test A No Start Condition (Dodge 3.9L, 5.2L, 5.9L).
- How To Test The Fuel Injectors (Dodge 3.9L, 5.2L, 5.9L).
- How To Test Engine Compression (Chrysler 3.9L, 5.2L, 5.9L).
- How To Test The Ignition Coil -No Start Tests (Chrysler 3.9L, 5.2L, 5.9L).
If this info saved the day, buy me a beer!