Electrical issues that I suck at diagnosing

[barnfindseries3ffr]

The '87 v8 starter motor was spinning but not throwing the gear to the fly wheel so it sounded like a fan running on.
I removed it in the Woolies car park and replaced it with one I salvaged out of a' 90 3.9.
It fired up no problems for about 9-10 starts and drives until it started up and continued to run even with the key turned off. So I disconnected the negative terminal.
I'm hopeless with electric stuff and I believe that the problem is not originally the starters as it is 2 in very quick succession.
Where do I look?

[barnfindseries3ffr]

And I should also put that the alternator fried itself about a month ago and I replaced it with the one from the '90 3.9.

[DoubleChevron]

sounds like either the ignition or starter solenoid relay is sticking in the start position.......


seeya
Shane L.

[aussiebushman]

Quite seriously, give the solenoid (not the starter) a few good wacks with a hammer. They do rust inside and this is a proven way to loosen them up

[DoubleChevron]

Quite seriously, give the solenoid (not the starter) a few good wacks with a hammer. They do rust inside and this is a proven way to loosen them up

I find that usually knocks worn out brushes back into contact with the commutator ..... A **very** short term fix!

[Blknight.aus]

3 possible electrical iissues.

1. the alternator is backfeeding the ignition due to a failure in the regulator pack
2. the startermotor is backfeeding the igntion through the hold in winding in the starter solenoid due to a burnt or damaged pull in winding.
3. the ignition switch has burnt and sticking contacts.

easy to test, unplug the alternator unplug the signal wire off the starter, turn the key to on and then bridge the hot pole on the starter solenoid to the signal to get it to wind over and start.

with it started turn the ignition off. if it keeps going its not the starter or the alternator.

the next bit is a bit harder and involves mimicking the action of the ignition switch as well as metering the ignition switch.

if it shuts down plug the alternator back in. repeat the test. if it keeps running now you have the culprit. its the alternator.

if it doesnt keep running wire the starter motor back up and start it. IF it keeps running now the issue is the starter.

good luck with it.

It might also be the ingition relay fusing closed if its fitted with one.