I’ve read about that exact same symptom in a different “no spark” thread here on dmctalk. Or maybe on the eurotech forum.
Sadly I don’t remember what the cause was...
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Checking spark from coil to distributor:
https://www.facebook.com/sveinapelan...382510259/?t=0
Checking spark on plugs:
https://www.facebook.com/sveinapelan...393000259/?t=0
Connected a test light between negative post on coil and battery positive post to see if light flashes on and off, meaning Pickup and ECU should be ok:
https://www.facebook.com/sveinapelan...399200259/?t=0
Did you ever get spark to jump from the coil tower to a ground or neg post on the coil?
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Either coil should spark according to those readings....try the test I posted above to confirm if the below doesn't help.
If the battery will crank the engine over ok by itself, it is hot enough for spark.
Sparking only when you shut the ignition off suggests that the coils trigger circuit is always grounded. (It would fire whichever plug the rotor happened to be pointed at when the key was turned to OFF.) But if that were the case, the ignition tester (and tach) shouldn't be indicating continuous spark while you crank it over.
So, the only thing I can think of that may fit is a cap with its coil terminal shorted to the plug terminal feeding the only plug you are seeing fire...
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No. The ignition doesn't need the RPM relay.
If there are no shorted wires etc. between them it doesn't matter WRT no spark. The relay uses the tach signal to know it is ok to supply power to the fuel pump and CPR.
P.S. Your Facebook links require an account....
Testing Distributor from negative terminal to battery positive post Delorean
https://youtu.be/oHRR7ZB-ufs
Testing spark from coil wire to distributor cap Delorean
https://youtu.be/bmkuDlzQZ0A
Testing spark from sparkplug wire to sparkplug Delorean
https://youtu.be/x3NxgwJnDpI
Was the king lead from the coil to the distributor ever changed? Or is it still the old red one?
Well... Its barely used, but bought 8 years ago. Thinking of the condition the cap and rotor is in, I ordered new wires and plugs with the cap and rotor.
Last time it would not start it was exactly this I had to change. This was right before I started the restoration.
Original NOS? As I've found they don't age well if it's an original red type lead.