Technical How do you test a GM 4 pin module

Hey guys
I have lost spark at my coil, went to NAPA got another module and the same thing, no spark
So I'm wanting to know how to rest a 4 pin module.
Thank
Mike

 

If you replace it with a new module, and it still doesn't work, then it's probably something besides the module. Like the coil, pickup, wiring, cap, rotor, power source, etc.

there's a pretty good diagnostic chart for the early HEI in the 1970s GM shop manuals.

http://www.autozone.com/repairguide...em/Diagnosis-and-Testing/_/P-0900c1528007d96a

 

Take an ohmmeter and connect it to the white and green leads on the pickup coil and move the wires every way possible. I suspect you will find an intermittent open circuit in those as they are very commonly broken due to very fine and flexible wires.

 

Agree with above. Have repaired 2 due to break in wire. Believe it's from the advance plate going through the motions, repeatedly.

 

Before you plug in a new module check the coil for shorted winding. Supposedly defective coils are the cause of a lot fried modules.

 

That unit puts out a hefty spark. Check the rotor. The metal strip on top of the rotor, that contacts the button from the coil above, just below that rotor metal strip, it will arc a hole through the rotor plastic and sending your spark directly to ground.