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MG MGB GT V8 Factory Originals Technical - Starter Motor problem - or is it?

Hi Guys,

I have an unusual problem with my '78 BGT starter. I'm using the standard, Lucas pre-engaged starter motor on my Rover V8 conversion. The engine is an old, ex-Costello engine, which still uses the original MGB starter motor not the Rover starter).

When I turn the key, I can hear the solenoid pull in and the starter motor always turns but only sometimes does the car's engine turn over. I've heard of plenty of intermittent electrical problems but this seems to be an intermittent mechanical problem.

If the solenoid has pulled in to apply power to the starter motor, I would have expected the pinion to have been pushed into engagement with the starter ring on the flywheel but this doesn't seem to happen every time. By the way, it seems worse when the engine and starter are hot; there are no nasty noises.

Any ideas would be very welcome.

Regards

Peter
Peter Hills

Peter
I suspect the motor is not man enough but it would do no harm to fit another earth strap between the engine and the chassis.
Roger
Roger

What are the flywheel and pinion teeth like? Like you say, the whole point of the pre-engaged starter is that the pinion is supposed to be engaged with the flywheel before the solenoid applies power to the motor, meaning that the starter shouldn't be able to spin without turning the engine. If it were not man enough it would engage but not spin. Either the teeth are not engaging for some reason (wear or breakage) or possibly the solenoid contacts are closing too soon and stopping the pinion engaing fully.
Paul Hunt

It sounds as if the solenoid is sticking. It is sometimes moving far enough to operate the starter proper and sometimes not. It is a bit puzzling that the solenoid is engaging electrically before the starter is engaged mechanically. They do gather a lot of muck internally over time so a good strip and clean may fix it. I guess that you are about to embark on what can be one of the most frustrating jobs on these cars - removing the starter motor. Good Luck.

Ian Thomson.
ian thomson

With tubular manifolds I can get my starter off and on without removing anything else except the heat-shield by using a set of 3/8" extensions and UJ between the manifold pipes to get to the top bolt. The bottom is easy, of course.
Paul Hunt

I've seen the ring gear slip and cause this problem. The starter sounds like it's spinning over because it is. The ring gear just spins on the flywheel.

Kelly
Kelly Combes

I forgot to add, only when hot.
Kelly Combes

Hi Guys,

Thanks for your advice. Following your advice, and those from the main MGB threads, I changed the starter motor for a newly reconditioned one from Moss.

Unfortunately after a couple of hours of cursing, swearing and breaking my fingernails - Sorry Paul, even the bottom screw didn't want to go back easily - I was very disapointed to find that the symptons were still there. Tomorrow, I shall lie under the car again and take the new starter motor off, examine it, test it off-line and try to peer into the dark hole to look at the teeth on the starter-ring. From what I remember - going back to last autumn - I'm not expecting to find tooth-damage on either pinion or starter ring.

Sounds horribly like time to take the engine out again and check fits carefully when I can see things properly!

Yours frustratedly

Peter
Peter Hills

How many different positions does a V8 engine tend to stop in? For a four-cylinder it is only two meaning that only two places on the ring-gear take most of the initial impact. The next time it does it try rotating the engine manually a few degrees and trying again. Seems to me that if your diagnosis is correct (motor turns but not engine) it can only be the ring gear.
Paul Hunt

This thread was discussed between 30/03/2003 and 03/04/2003

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