TEST 1: Applying 12 Volts To The S Terminal
The first thing that we're gonna' do is apply 12 Volts to the starter motor solenoid's S terminal to see if the starter motor will crank the engine.
If the starter motor cranks the engine, then you can conclude that the starter motor itself is OK.
A remote starter switch will come in super handy when applying 12 Volts to the starter motor solenoid's S terminal.
Also, I use a wire piercing probe to pierce the S terminal wire and then connect my remote starter switch to it and proceed from there; I suggest you do the same. You can see what this tool looks like here: Wire Piercing Probe Tool Review (Power Probe PWPPPPP01).
IMPORTANT: Remove the key from the ignition switch for this test.
OK, this is what you'll need to do:
Raise your E-Series van and place on it jack stands. Remember, the only way to gain access to the starter motor is from underneath the vehicle.
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.
Attach a 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.
Reconnect the battery negative (-) cable to the battery negative (-) post.
Now, apply 12 Volts to the S terminal wire of the starter motor starter solenoid with your remote starter switch.
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 is the correct and expected test result.
With this test result we can usually conclude that the starter motor is not receiving a 'Start' signal if the starter motor does not crank the engine when you turn the key to start it.
The next step is to verify if the 'Start' signal is missing. Go to: TEST 2: Verifying The 12 Volt Start Signal.
CASE 2: The starter motor DID NOT crank the engine. Double check your connections and repeat the test.
If the starter motor still does not crank the engine, then this usually means that the starter motor is bad and needs to be replaced.
Before you run out to buy it, you need to make sure that the battery (+) cable does not have a voltage drop issue. Go to: TEST 4: Voltage Drop Testing The Battery Cable.
TEST 2: Verifying The 12 Volt Start Signal
When you turn the key to crank the engine, the starter motor solenoid receives a 12 Volt 'Start' signal from the starter motor relay.
This 'Start' signal is delivered to the starter motor solenoid's S terminal. In the photo above, the S terminal is labeled with the letter S.
In this test section, we're gonna' confirm the delivery of this 12 Volts 'Start' signal to the starter motor solenoid's S terminal.
OK, let's get testing:
Set your multimeter to Volts DC mode.
Connect the red multimeter test lead to the wire that connects to the starter motor solenoid's S terminal using an appropriate tool.
Don't know which wire is the S terminal wire? This is the one that connects to the smaller of the three studs on the starter motor solenoid.
The S terminal wire (circuit) is the one that delivers the Start (Crank) signal from the starter motor relay.
Ground the black multimeter test lead directly on the negative (-) battery terminal using a jump start cable.
You can also Ground it on the engine, if you can find a clean, unpainted and rust-free spot of metal.
When everything is ready, have your helper turn the key to crank the engine.
Your multimeter should read one of two results:
1.) 10 to 12 Volts DC.
2.) 0 Volts DC.
OK, let's examine your test result:
CASE 1: Your multimeter DID NOT register 10 to 12 Volts. This test result tells you that the starter motor is not receiving an activation signal from the starter motor relay.
The next step is to make sure that the starter motor relay is getting its activation signal. Go to: TEST 3: Testing The Starter Motor Relay's Activation Signal.
CASE 2: Your multimeter registered 10 to 12 Volts. This is the correct and expected test result and it tells you that the starter motor is receiving an activation signal from the starter motor relay.
At this point, you have:
- Confirmed that directly applying 12 Volts to the starter motor solenoid's S terminal makes the starter crank the engine (TEST 1).
- Confirmed in this test section that the 'Start' signal is being delivered to the starter motor.
With these test results you can conclude that at this time the starter motor problem is not present. You'll need to wait till the starter motor does not crank the engine to continue troubleshooting the problem.