Sigma starter motor problem - help please

[Garth]

Towards the end of a track day last week my starter motor stopped working. It was making a high pitched whirring sound but no engagement with the flywheel. Thought the drive gear might be a bit sticky and a tap on the side of the unit got it working until the next time it was needed! I have since done the following;

1. Earthed the block separately to make sure it is not a poor earth

2. Removed the starter motor, gave it a good clean (but it was not too dirty anyway!)

3. Tested it out of the car - it appears to work - drive gear shoots forward and spins

4. Put it back in, same problem!

5. Battery seems fine but hooked up to my tintop battery just to be sure. Same problem!

I know of a local man who rebuilds starter motors, but wondered if there was any wisdom from within before I seek him out?

I have been told that modern starter motors do not like being tapped on the side - it does not help and is more likely to break them?

Thanks in advance.

Garth

 

[Jonathan Kay]

I think it's probably a fault within the starter, but I'd take the electrical checks a bit further:

1. What's the battery voltage at rest and minimum seen during cranking (you can do the latter with the jump battery connected if you choose)?
2. You've put in a good earth. Now inspect and wiggle all the other relevant wires and disconnect, clean and reconnect all the connections. That's everything at the starter and the battery and the thin wire(s) to the starter solenoid.

Jonathan

PS: As well as clouting them when they're sticky you can turn the ignition off, put the car in gear and push it a bit.

[Garth]

Thanks Jonathan

Did not check the voltage on the battery as I assumed that putting it in parallel with my other car's battery (and keeping it running) would ensure there was enough juice?

Have cleaned and remade all the positive and solenoid connections. Thinking it must be a problem with the starter - that even though it appears to be working, when it is under load something is 'slipping'?

I tried moving the flywheel slightly by moving it in gear - the starter did still not appear to engage (unless is is engaging but then not driving (as the drive gear is slipping on the spindle (or whatever drives it?)

Thanks

Garth

 

[Garth]

I think this starter has a clutch drive to turn the drive gear - perhaps this is gone?

[Jonathan Kay]

Did not check the voltage on the battery as I assumed that putting it in parallel with my other car's battery (and keeping it running) would ensure there was enough juice?

Usually yes. But that relies on the assumption of good contacts, and if jumping, that the 7's battery etc isn't pulling the other one down.

And that's only the first part of the test: if there's enough oomph across the battery when cranking you can then test if it's getting to the starter.

Jonathan

[Jonathan Kay]

I tried moving the flywheel slightly by moving it in gear - the starter did still not appear to engage (unless is is engaging but then not driving (as the drive gear is slipping on the spindle (or whatever drives it?)

Sorry, that was generic advice for sticking when engaged, not your failure to engage.

Jonathan

[Garth]

Sorted thanks - evidently an issue with some internal gears - looked like it was working under no load. Found a very helpful local man who has been rebuilding alternators and starter motors for 48 years! £98 and an hour later all sorted. 

Now just to put it back in the car...