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MG MGB Technical - Starter intermittent

Hi Folks

On my late 72-build roadster the starter has been intermittently only giving a solid metallic clunk from the solenoid but with no rotation. After a number of turns of the key the motor spins and cranks ok. The problem is now getting a good bit worse with 20 turns of the key today to get the motor to turn. I had thought of the starter pinion failing to mesh and holding the mechanism back but rocking the car in gear to change the engine position 3 times didnt help. I have also checked the solenoid current which stays up at 45 amps or so when the fault is on indicating that the high-current pull-in sol. winding is not being shunted out. (The current falls to around 10 amps as it should when it cranks). The solenoid contact asssembly is I think suspect.
I need to fix this asap and would value any wisdom re the best approach. So far I am of a mind to simply get an exchange unit and would appreciate anyone's experiences with the various sources of supply.

Noble M.
N. Macpherson

N. sounds like it's time for a starter,solonoid replacement will more then likely be a waste of time. RIC
R E L Lloyd

Noble

This sounds similar to a problem I have been experiencing with my 80GT. I had installed a reconditioned motor which was fine for a while but every now and then takes a large number of turns of the key to rotate. I phoned the guys I bought it off and he suggested looking at the starter relay fixed to the inner wing. This has a crack running through it!!! I'll be replacing this next. May be worth checking before pulling the starter.

Regards

Darren
D Paine

If you are getting the clonk from the solenoid but no rotation then the electrics down to that point, including the relay, must be OK. Together with the hold-in current remaining at pull-in levels it sounds like the solenoid isn't moving far enough to disconnect the pull-in winding *or* close the motor contacts, rather than just the motor contacts being the problem, i.e. a mechanical problem. If the current was dropping I would say it was the solenoid contacts, or possibly the motor brushes or a dead segment.
Paul Hunt

Try switching the headlights on before turning the key. If the starter works OK, rewire the feed from the motor up to the starter relay, (on mine it's located next to the fusebox on the rh inner wing).

Don't ask me how the headlight thing works - the auto electrician who told me about it didn't know either - but it worked.
C Linn

Whilst the headlights and the starter relay share a grounding point, which if bad can explain why they sometimes interact, in this case the solenoid is clonking which definitely points to problem inside it or the motor.
Paul Hunt

This thread was discussed between 15/08/2004 and 20/08/2004

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