Lost voltage to coil when cranking engine

[sjp63]

Hi

I have a sudden fault on my Bristol (chrysler V8) When cranking the starter the voltage to the coil goes to zero and only comes back when you stop cranking. Its been concerted to electronic ignition a long time ago so i suspect it no longer has a ballast resistor but not sure. Any work arounds??

Any ideas?

[stevieturbo]

faulty ignition switch.

[Yuxi]

Take a wire from the solenoid on the starter motor (the small one from the ign switch) to the coil as a tempory measure, then find the fault and mend it.

[Pigeon]

No, don't do that, or the supply to the coil when the ignition switch is in the "run" position will keep the starter engaged...

The temporary workaround is to fit a starter button so you can work the starter while leaving the ignition switch in the "run" position.

[rev-erend]

If you have 12v when not cranking the as said above the fault lies within the ingition switch and not a faulty wire somewhere.

[sjp63]

Pigeon said:

No, don't do that, or the supply to the coil when the ignition switch is in the "run" position will keep the starter engaged...

The temporary workaround is to fit a starter button so you can work the starter while leaving the ignition switch in the "run" position.

correct - i already found that out!

ive taken a wire to the coil from the sidelight circuit which stays live when cranking the starter. Just temporary whilst i find the fault

how hard to fit new ign switch?

Edited by sjp63 on Monday 8th March 19:26

Edited by sjp63 on Monday 8th March 19:26

[stevieturbo]

sjp63 said:

how hard to fit new ign switch?

Questions like this are great.

its very easy if its car with an ignition switch is easy to access, and you have all the tools and skills to do it.


If its a nightmare to access and you have no tools, and dont know which end of a screwdriver to use....then it could be a difficult task.

[Yuxi]

Pigeon said:

No, don't do that, or the supply to the coil when the ignition switch is in the "run" position will keep the starter engaged...

The temporary workaround is to fit a starter button so you can work the starter while leaving the ignition switch in the "run" position.

You are quite right of course, I was havinga "senior" moment. Apologies!!

It could still be a wire off somewhere, my car (1972 Scimitar GTE) has a seperate inner wing mounted starter solenoid with a small spade connection that goes +12v when the key is in the start position, independant of the +12v thick wire to the starter. This small connector is connected to the coil. This gives 12v to the coil when the key is in the start position, the coil then goes back to about 9v through the strangley named "eureka joint" when the key is in run position.

[oakdale]

If you look at the starter motor solenoid, there should be two small wire connections, one is the instigater lead (The one that the switch feeds to operate the starter) and the other one is the feed to the coil from the solenoid during cranking.

The fault is most likely in the connection or wire of this feed to the coil (or the starter soleoid itself).

Edited by oakdale on Tuesday 9th March 00:01