GM HEI troubleshooting: Project S-10

If I had any hair, I would tear it out.

To recap: this is an '87 Chevy S-10, with a TBI Iron Duke 2.5 I-4.

Truck would not pass smog due to a severe misfire under load. Replaced lots of parts. On the last test drive around the block, the truck coughed and sputtered its way back into the driveway, and now is a total no-start.

Latest update: Fat, juicy spark at the (external) coil. No spark at any plug wire. Cap, rotor, wires, and plugs all new.

I have verified that the rotor is, well, rotating, thus eliminating any mechanical failure of the distributor drive.

Rock Auto tells me there is an "Ignition Pickup" (Hall effect sender, I'm thinking) and an "Ignition Control Module" inside the distributor. It would certainly seem that either of these could cause the problems.

Unfortunately, most Internet HEI troubleshooting guides cover the coil-in-cap V-8 ignitions.

Any insight is greatly appreciated.

The common problems with the HEI are the module (under the cap) or the wires for the pickup shorting to the case where the exit the distributor (out the bottom). The module can be taken to an autoparts store to be tested, replacements are cheap. To check the wires try moving them around a little to see if the problem changes. Niether of these suggestions explains why you would have spark at the coil but not the plugs the only cause I can think of for that is a bad coil wire that is either open or shorted to ground or the rotor is out of phase with the cap terminals by enough that it cant fire.