I have replaced everything in the ignition system except the computer and still have no spark. Got power to the distributor. New Distributor and trigger coil, ECM, Coil, Ignition switch, and Rotor. It looks like the three wires coming out of the ECM in the distributor go into the harness and to the computer behind the glove box. Don't know if it controls the spark or just adjusts it. Anyone know if it can kill the spark? I know the coil is working in the distributor.

 

what about the ignition module under the distributor cab. its a little black half moon thing with either 4 or 7 wires going to it.

 

this is what an icm looks like



some look a tad different but this is what came up for an 86 k5

this would stop the spark if it went bad
some auto parts test them also

 

According to this.. Part 5 -GM Distributor Mounted Ignition Module (ICM) Test. .. the ECM only advances the timing once the engine reaches 400 rpm, otherwise the coil is fired at base timing by the ICM.

That makes sense, but on Fords, the ICM wont fire at all if the ECM is connected through SPOUT and doesnt send the signal, so if you disconnect the same lead as disconnected for setting base, the ford ICM will fire the coil.
It COULD be that the GM ICM works the same way. In that case, if the coil fires with the base time connector open then problems in the ECM.
Another thing to check is if the injectors are firing. If they are, it probably isnt the ICM.

 

i remember when my icm failed i was not getting spark from the coil