How To Test The Starter Motor (1991-1995 3.9L Dodge Dakota)

TEST 4: Making Sure The Starter Motor Is Getting A Start Signal

So far you have confirmed that:

• The starter motor DOES NOT crank the engine when you bypass the starter motor relay (TEST 1).
• Female terminal B (of the starter relay socket) has 10 to 12 Volts (TEST 2).
• The starter motor cranks the engine only when you apply battery power to the starter solenoid's S terminal (TEST 3).

Our next step is to see if the Start Signal is present in the wire that connects to the S terminal of the starter motor.

The start signal is only present when the ignition key is turned to crank and start the engine.

These are the test steps:

1. 1

   Install the starter motor relay in Power Distribution Center.
   
   NOTE: This test is done with the starter motor relay in its place on Power Distribution Center.

2. 2

   Disconnect the wire that connects to the starter motor solenoid's S terminal.

3. 3

   Connect the black multimeter test lead to the battery negative (-) terminal.

4. 4

   Connect the red multimeter test lead to the round terminal of the S Terminal wire you just disconnected in step 2.

5. 5

   Depress the clutch pedal till it bottoms out (standard transmission equipped Dodge Dakota only).
   
   This test will not function without depressing the clutch pedal (standard transmission only).

6. 6

   Have your helper turn the key to start the engine.

7. 7

   Your multimeter should register 10 to 12 Volts DC.

Let's examine your test results:

CASE 1: The multimeter registered 10 to 12 Volts DC. This is the correct test result and lets you know that the starter motor is getting a Start Signal. You can also conclude that the park/neutral safety switch and ignition switch are OK.

The next step is to do a voltage drop test on the starter's battery cable. For this test go to: TEST 5: Voltage Drop Testing The Battery (+) Cable.

CASE 2: The multimeter DID NOT register 10 to 12 Volts DC. This lack of voltage lets you know that the Start Signal is not being supplied to the starter motor. Without the Start signal the starter motor will not crank the engine.

If you have:

• Bypassed the park/neutral safety switch in TEST 1 and the starter motor DID NOT crank the engine.
• Applied 12 Volts to the S terminal and the starter did crank the engine (TEST 2).

Then this result tells you that one of the following problems is causing the lack of the Start Signal on the S terminal wire:

• The starter motor relay is bad.
• The ignition switch is bad.
• The park/neutral safety switch is bad (automatic transmission).
• The clutch switch is bad (standard transmission).
• The S Terminal wire has an open-circuit problem between its connector and the starter motor relay's connector in Power Distribution Center.

TEST 5: Voltage Drop Testing The Battery (+) Cable

In some cases, the starter motor does not crank the engine because it's not receiving the full amount of current the battery can supply.

This usually happens when there's hidden corrosion on:

• The battery cable terminals.
• The battery posts.
• The round terminal that connects the battery cable to the starter motor.

So in this section we're gonna' do a simple multimeter voltage drop test on the battery positive cable and make sure it's not keeping the starter motor from receiving all of the current the battery can supply.

IMPORTANT: The battery must be connected to its two battery cables. The starter motor relay must be in its place in Power Distribution Center. The S terminal wire must be connected to the S terminal on the starter motor solenoid. The battery (+) cable must be connected to the starter motor.

CAUTION: You'll need to raise your 3.9L V6 Dodge Dakota to access the starter motor. Use jack stands to keep it up. Don't trust the jack!

These are the test steps:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Attach the black 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 lead make contact right in the center of the positive battery post.

3. 3

   Connect the black multimeter test lead to the center of the stud to which the big battery cable attaches to on the starter solenoid.

4. 4

   Depress the clutch pedal till it bottoms out (standard transmission equipped Dodge Dakota only).
   
   This test will not function without depressing the clutch pedal (standard transmission only).

5. 5

   Have a helper crank the engine.
   
   This is important, since a voltage drop test has to be done while the component in question is working (or trying to work).

6. 6

   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 (which is bad), your multimeter will register voltage (usually above 7 Volts DC.)

Let's take a look at what your results mean:

CASE 1: Your multimeter registered 0 Volts (no voltage drop). This is the correct test result and tells you that the starter motor is receiving all of the battery current it needs to crank your Dodge Dakota's engine.

You can conclude the starter motor is bad if you have:

1. Confirmed that the starter motor DOES NOT crank the engine when you bypass the starter motor relay (TEST 1).
2. Confirmed that terminal B of the starter motor relay socket has 10 to 12 Volts DC (TEST 2).
3. Confirmed that the starter motor DOES NOT crank the engine when you apply battery power to the S terminal of the starter motor's solenoid (TEST 3).
4. Confirmed that the starter motor is receiving a Start Signal (TEST 4).
5. Confirmed that no voltage drop exists on the battery positive cable (this test step).

Replacing the starter motor should solve your no-crank condition.

I'm going to make two more recommendations to you:

• Before removing the starter motor, manually turn the engine using a 1/2 ratchet and the appropriate socket on the crankshaft pulley. This is to make sure that the engine or the A/C compressor have not locked-up. If the engine is locked-up then the engine will not crank and it'll look like the starter motor is at fault.
• Bench test the starter motor after removing it. This is a super easy test to do and this tutorial will help: Bench Testing The Starter Motor.

CASE 2: Your multimeter registered 5 Volts or more. This result tells you that a voltage drop does exist and that full battery current is not reaching the starter motor.

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 that connects to the starter motor's battery (+) cable stud.

After cleaning, try cranking the engine. If it cranks and starts, no further testing is required.