Weird spark issue

[Toon]

Ok, I am having trouble with my '86 720 pick up.  Died while driving, no spark condition.  I am not too familial with dual spark plug ignition so I would like some quick help as I need transportation asap.

 

In an effort to trace the loss of spark I found that the motor would run with either coil lead unplugged, but spark was gone as soon as both coils were plugged in to the cap.  Pulled the exhaust side coil and limped it home on one set of plugs, and now I have no clue where to look next. 

 

So, both coils are give good spark, but I need some help or ideas as so why i would loose spark when both coil leads were plugged into the dizzy cap. Pulled cap and looked normal? Not sure what normal is but it wasn't too fried.  How safe is it to drive around with one of the coils disconnected?

 

 

 

Thanks All

Toon

[datzenmike]

Yes you can run on one set of wires but the timing will be badly retarded. Poor mileage and power. You could run the advance up around 10-12 degrees but better to fix what's wrong.

 

 

Pulled cap and looked normal? Not sure what normal is but it wasn't too fried.  How safe is it to drive around with one of the coils disconnected?

.

 

Well " wasn't too fried" says:... get a new rotor and cap. There's no reason why spark shouldn't get through with both coil high tension leads on the cap. Maybe cap or rotor are cracked.

[vanmansam]

Toon is my friend and I have been helping. I am guessing cap and rotor as well.

[datzenmike]

No way the spark can be stopped from doing this... but it maybe could be diverted somewhere under the cap.

[vanmansam]

Dylan came over for some help tonight, rotor was toast. A hole eroded in the "wall" between the inner and outer riders. Sorry if this makes no sense cause I dont know how else to describe it, but basically the cap was NFG so both coils were arcing like crazy inside the cap.

New rotor and cap solved the problem, and the truck runs great.

Thanks Mike.