I have an issue with the ignition system on my 993. The problems began when the engine suddenly started hesitating through the rev range and whilst I think I've found the cause I just wanted to check with you knowledgeable chaps....

During my investigations I've replaced the distributor caps and rotor arms since they've never been changed (to my knowledge)....one rotor arm was really burnt. I've also checked the dual distributor belt and that looks fine. The problem now seems to be that one of the coils has failed. I proved this by disconnecting the top coil HT lead and the engine started. I then reconnected and disconnected the lower coil lead and the engine failed to start. So there is a problem with the top distributor circuit. I then connected the top distributor HT lead to the lower Coil and the car started. So it looks to me like the top distributor coil has failed

I've seen a post that says to check that 12v is going to the black wire on the coil when the ignition is on and 12v is present. The only thing I can't test is the other connection which I think comes from the ECU. So my question is....if the other coil is working do the green wires go back to the same point in the ECU? Therefore it's definitely a coil failure ? I've read that it's not uncommon for these to fail, but I just wanted to check.

Thanks in advance

 

I don't know where the green wires go, but you could disconnect them all and swap the coils over completely. That way you can rule out the wiring / ECU and be sure it's that coil.

 

The black wires are the 12 power feed to the coils. The green wires go back to the dual ignition module . If you swap the green wires over on the working coil that will tell you if you have a module failure .
The 964 had two seperate modules , each with its own plug so that was easier ?

Good luck

Geoff

 

Thanks for the replies. I took your advice and swapped over the feeds to the coils from the ECU and thankfully the suspected dead coil didn't start working and the other coil was still working fine when doing the disconnect one HT lead test.

So at least I've only got to replace the coils which is no doubt cheaper than anything ECU related.

Thanks again