Problem with HEI in a 366 V-8 GMC truck.

[bstrom1953]

My truck just quit. No spark. HEI system. Did some troubleshooting. Replaced the module in the distributor and then replaced the coil too. Still nothing. I have 9.6 volts at the BAT terminal while cranking. Tach terminal has greater than 10 volts. Coil is grounded properly, I checked it with an ohmmeter plus grounded it with jumper. The cap in the distributor checks fine, not shorted or open. Can the reluctor go bad? How do you test it? Help, thanks.

[MagicRat]

I might suggest new cap, rotor and try another high voltage coil wire (to the distributor)

[bstrom1953]

Thanks for the tip. I did get the truck to run by replacing the rotor. I was able to determine that I had good spark at the output of the coil but a super weak spark at a plug. The only thing in the path was the rotor and cap. After inspecting the rotor I discovered a black spot where the HV had bored through the plastic and was shorting out on the spark advance mechanism. Thanks again!

[JustSayGo]

Bad ignition modules cause HEI to produce unregulated max voltage that burns through the rotor. Inspect the sparkplugs to see if they are burned up as well.