Starter elecrics and intermittent stater op.

[pebattrick]

Continuing my previous post. Has anyone had issues with the battery to starter cable running from the battery through the tunnel. Can internal corrosion or possibly partial breakage be an issue and drop some volts. After all the cable is 2m + long and 35 yrs old (onon my car), not a simple job to replace. Likewise the crimped connections. Clutching at straws here.

 

[IndischRot]

The earth lead is the far more likely culprit. Do start there.

 

[geedee]

Sorry to read of your intermittent starter issues and can not recommend any one to effect repairs.
It seems you have an understanding of the basic low current circuit operation which by your description works to the extent that the solenoid mounted on the starter is activated, as indicated by the sound of a clunk but nothing beyond that..?
The solenoid mounted on the starter performs two functions when the low current coil within it is activated, the first of which is to draw a plunger into the now magnetised core of the solenoid. One end of the plunger acts on a lever which then attempts to engage the starter motor gears with the teeth on the flywheel... at the same time the the other end of the same plunger acts on HEAVY electrical contacts, which short out the two heavy wiring terminals terminals on the outside of the solenoid... one of which is the POSITIVEpower lead direct from the battery, the other being connected to to the internal windings of the starter MOTOR, when both are shorted together STARTER MOTOR turns
For this all to happen in the mechanical sense, the teeth in the gearing of the starter motor must match those in the flywheel for them to be able to engage fully. There is usually a chamfer on the leading edge of the teeth to assist engagement... and if for any reason the teeth do not fully engage then the plunger within the solenoid can not complete it`s travel to close the heavy electrical contacts to drive the starter motor... which seems to be the stage of the game you may have reached..?
Of course any dirty/cruddy connection in the high current wiring will provide similar results.
If you have not been able to determine the earth link body to engine/ gearbox assembly as being fully up to the task, then I guess you could use a set of jump leads linked together to provide a direct connection from the battery NEGATIVE terminal with one clamp end, and the other clamp end to a good clean and bare metal part of the engine/gearbox assembly, and then try for a start. The electricity does not care as to the colour of the insulation on the jump leads... just that YOU have to be well aware of what to connect to.. Nothing will be carrying current until you turn the key into the start position.
You could pull the DME relay to avoid the engine actually firing up, and thus then be able try numerous attempts without the engine firing up..? If it turns over numerous times and without issue then you may well have found the cause...?
Should you be tempted to use a bit of wire you have lying around and not of the required current carrying capacity, it could heat up and melt or set fire to the insulation along it`s entire length with who knows what consequences..?
Good luck..Please let us know how you get on.

 

[Targatopp]

Hi I have a 1984 carrera 3.2 and was plagued for 10 yrs of intermitant starter failure, not even a clunk.Having changed most things eg starter ,gbox earth wire , replaced immobiliser.

I did voltage drop tests on both live and neutral and both looked ok.
I narrowed it down to two possible causes
1 starter switch sticky and not turning to start position eevery time so I marked the start position with a piece of white tape on the key surround plastic as a point of reference.

2 I put a new temporary solenoid wire on the starter and ran it back through the car into the front boot area .there is a wiring harness coming from the ignition switch to the bulkhead .The solenoid wire is yellow and runs back through the car to the engine bar into a connector block which enables the wiring to the engine to be easily disconnected when you do an engine drop.

In my case I connected the new solenoid wire to the ignition switch yellow in the front boot and this was to eliminate possible faulty wiring through the cars harness via the engine bay into the starter.

as belt and braces I extended the now disconnected yellow solenoid wire and ran it to the battery area and insulated it.(This wire should go live every time the starter is fired by the temp wiring).

The purpose of having this second original wire was to bypass the ignition switch in the event that it was the faulty element by simply flashing it onto the live battery to close the solenoid.

To date my temp wiring fix is working but I dont know 100% if its the starter switch position or the old yellow solenoid wiring through the car that was causing the issue

hope that helps

Paul

 

[pebattrick]

Thanks to all for the helpful and constructive comments and answers on my post. The solution turned out to be a worn throw out clutch on the starter motor. It manifested itself by exploding and leaving small bits in the bell housing. I have a rebuilt starter motor a new ring gear and a thorough cleanup of flywheel, cavity clutch etc. and fingers crossed all good. I was recommended to an excellent "old school" starter and automotive repair shop by my local vintage car restorers (AK Vintage Restorers). The repair shop is called, imaginatively, Starter and Alternator Centre, Cinderford. I can't recommend them too highly. Fair price, quick turnaround. They even sorted the starter on my Moto Guzzi California which has been giving me the same trouble.
Happy days, all I need is to get my shoulder replacement back working and I can have some summer fun in the 911.