James Stockhold

I have a 1991 GMC Sierra 1500 4.3L that was gifted to me with a problem of dying when warm and not restarting until cool but starting and running fine when it does cool. Now it wont catch at all do to no spark. Ive changed cap, rotor, plugs, ignition control module, pickup coil, external coil. Ive checked all fuses. Truck has full power so im doubting ign switch on top of column. With the key on i have constant power on the pink lead grey plugin from the ecm/ecu going into the coil. When i bridge same plug with key on usi g a test light between pink and white wires while disconnected from the coil i get nothing. When i go from same plug white wire to battery + with key on i still get nothing. Does that imply my ecu is bad or not getting/supplying power or could the ground be broken from ecu to coil? And, how would i proceed in terms of diagnosing/repairing?

Steve Stahl

I would think your on the right track....I'd look for a ecm a wrecking yard, or find a similar truck and try swapping the ecm.

There used to be a company the would rent you a ecm for a fee to trouble shoot.....Our ecms or something like that