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Published 2007

Bad Coil

Phil aka chopperpilot asks:

I have got the roadster running great. Engine is smooth with the new Z therapy carbs. I bought a used GB dizzy from the classifieds here. I am having a problem this AM with the car cutting out every little bit. I took it out this am going along and it died. I stared it back and and we limped back home. It would run pretty good have a big backfire and die. Start back up fairly quickly go a few blocks and repeat.

I got in the garage and started looking it over. I have tested the ignition pick-up and am right about 400 ohms. If I have the key on I show no voltage to the coil. This is measured at the neg term like the instructions say. The coil test.

When the car sits for 15-20 min It will start right up idle and rev for about 5 min then die. If I measure the voltage at the coil while it is running I get over 12 volts.

The car previously was not charging. I did put a new VR in today prior to the problems starting. The car is charging nicely now.

I ran the car all over heck yesterday never a stumble. Laughing

A long not but I am mystified. All signs point to the module according to the trouble shooting guide. Why would it be intermittent like that??

Mike aka Exit64 answers:

Sounds like you have a coil going bad. Start her up after dark and look for arching from the primary over to the secondary leads. I had one do the exact same thing once and about drove me over the edge trying to find the problem. Although it was in a Triumph with a Lucas coil so that should tell you something. Evil or Very Mad What happens is the coil builds up a charge like a capacitor and then stalls the car, after the car has been off for a few minutes it looses the charge, starts up like nothing is wrong and then starts the whole process all over again.