Weird no Crank/start situation

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Hi everyone,
I am facing a no crank issue with my 6A12 MIVEC converted 2001 Mirage Coupe (engine is from an FTO MIVEC). It used to start with this motor so this is not a post conversion issue.

I originally suspected it was a starter motor issue and performed the following tests:
1. Checked the voltage of the battery (12.6v)

2. Checked the direct battery positive feed to the starter has voltage; it does however I did not record the voltage so cannot comment currently (will perform this test tomorrow)

3. Checked that the starter solenoid (S terminal) is receiving voltage once ignition is turned; 10.3v was registered which is within “normal” even though a 2.3v volt drop seems excessive (more on this later as something odd happened with this test)

4. Checked for voltage from the solenoid directly to the actual starter motor while turning the ignition on; 0v registered. At this stage I thought “Ok, problem is with the starter solenoid”

Odd behavior in test 3:
The voltage would go up to 10.3v when I tried to start the motor at the starter solenoid. Then when I stopped trying to crank the motor and just left they key at “on” in the ignition the voltage was at 9.5v (I was expecting unless I am trying to crank this should be 0). Finally when I turn the key to the off position the voltage takes about 3-5 seconds to slowly drop
At this stage I removed the starter motor thinking it needs replacing and while out I bench tested it directly with the car battery. The pinion spring up and the starter motor started spinning very quickly, so it seems the starter motor and solenoid are fine.

What could my problem be?
Starter motor relay?

Tomorrow I will reinstalled the starter motor and try to connect the solenoid S (ignition/crank) terminal directly to the battery live feed that goes to the starter solenoid.

Any other tests I should perform?
Any ideas of what this could be?

If it is the starter motor relay, is this a common part on other Mitsubishis that are more easily found at wreckers?
 
Check the grounds. Also check the big wire from the battery to the starter under load. If you have voltage to the starter on the little wire from the key but none on the big wire, the starter will click but not turn.

Your idea to jump the S terminal to the battery is a good one, it will bypass the key switch neutral switch and any relays in the car, so you can concentrate on the major parts of the battery, starter, and connections between them, including the ground cable(s).
 
Check the ground wire from the starter motor:

starter.gif


Quote:
Checking the earthing of the circuit:

To check for a high resistance on the earth side of the starter circuit, connect the voltmeter to the battery earth terminal and earth it on the starter casing.

To check whether there is high resistance in the wiring on the earth side of the circuit, connect the positive lead of the voltmeter to the negative-earthed terminal of the battery, and the negative lead to the body of the starter.

Working the starter switch should cause a drop from 12 volts to below 0.5 volts.

If the voltmeter reading stays above 0.5 volts, look for a bad connection at the battery earth strap (at either end) or the engine-to-body earth strap.



LINK
 
The starter is grounded by it's casing on the motor, but I will do a ground check as well.

I am also thinking about using jumper leads to:
A. Provide a direct earth from battery terminal to starter body
2. Provide a direct +12v from battery terminal to starter solenoid and the constant feed to the solenoid


Would bad grounding explain the odd volts I am getting at the solenoid S terminal, and how the volts linger rather than drop when I let go of the ignition start?
 
Put a booster relay on the solenoid wire, this will sort any low voltage issues to the solenoid. Pretty easy to make, most of my cars have them. Do a google on starter booster relay.
 
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