no spark while cranking but sparks after key turned back

[c10 custom]

i am having an issue with a 1981 chev truck 3 ton it has no spark
while cranking but when key is released it has spark the pink wire on
the distributor has power when key is in run position but goes out
when cranked and ignition module power wire is the same way could it be the ignition module any help would be great thank you

[ray_mcavoy]

That sounds like a problem with the ignition switch as opposed to the module.

The switch should supply power to the distributor in both the "run" and "start" positions.

[bnoon]

I agree with the switch.

[jjzepplin]

Had this happen in a FURD once. Started for a millisecond right when you gave up and shut it off.=Was the switch.

[wilkin250r]

I second the motion.

I imagine that up until now, you've been focused on the ignition module and distributor because you have an ignition problem, and that's perfectly reasonable. But let's take a step away from the trees for a second so we can look at the forest.

When you turn your key to the "start" position to crank your engine, you need power to the starter solenoid in order feed the starter motor, and also power to the ignition in order to get the spark to fire.

Once the engine fires, you let the key snap back to the "run" position, which should still supply power to the ignition to keep the engine running, but you no longer need power to the starter.

It sounds like your "start" position is indeed applying power to the starter motor, but you're missing the ignition power. You're cranking and cranking, but never firing. I agree with everybody else, your ignition problem isn't in the ignition components, it's in the switch.