No Ignition, real head-scratcher. Seemingly no HEI signal.

[ball]

Hey fellow astro-vanners,

So I got the van packed and ready for the weekend last night and then...the engine won't start! Tried various things until 5 in the morning so I'm pretty shot, but here is the run-down:

• No spark.

• I have a backup coil, ECU, and distributor so I first tried swapping the HEI module, coil, and even the ECU.

• I made sure the wires were all good including the four wires to the ECU.

• I'm nearly certain I'm getting no signal from the distributor. There is power to the coil, but spinning my spare distributor produces no movement on the tach (using an ancient tach/dwell device connected to the tach out on the coil). As I understand it, I should get some movement. Tapping battery positive makes the tach needle move, as does powering-off the coil (via the ignition key).

What could it be? :shrug: My current theories are:

1) I somehow have two bad modules which makes no sense to me because they both worked. I only switched distributors due to a mechanical issue. The spare module would have had to die the instant I connected it, which if true makes me wary of buying another. Is there any way to safely test a module?

2) Something else isn't getting power like the ECU? Not sure what are the symptoms of the ECU not getting power. I also only have one firmware module for this engine so I can't swap that. However, I don't think the ECU has to even be connected to the module for it to fire. I think the four pin connector is only to advance timing, otherwise I don't see how hotrodders use the 8 pin HEI unit for their projects. Can someone confirm?

3) ???

Oh yeah, drove the van yesterday no problem except for some reason the engine did die soon after it was started the first time. Drove it a few miles, parked, and now it's dead.

[ball]

I had both ignition modules tested at NAPA and they are fine.

This leaves, what, pickup coil? I got 0.3vAC out of the dizzy that's installed. I'll probably put the old one back in and see if that helps :\

[chesehd]

Do you have any codes?

[ball]

OBD1 typically doesn't have useful codes. I'll check if swapping the diff doesn't help. I have a cheat sheet in my GM service manual.

I also just tested the ohms on both coils and they were fine.

[ball]

OK, we can close this topic. I'm getting spark now.

Turns out it was a weak mag coil. I was getting .3VAC and it wasn't enough.