Howdy,
I have a '76 Ranchero with a 351m, and duraspark ignition system. While trying to reconnect the tach last week it dies and has not run since. We first thought it might be the coil, so we replaced it. No luck there. I then took the module down and had them test it, and they couldn't find any problems but replaced it for me anyway. No good either. Bought rebuilt distributor and installed it and that didn't do it. Went to junk yard and found a wiring harness (The one that goes from duraspark module to coil/distributor) and installed that with no luck. Measured resistance between the ends of the wires in the aforementioned harness, no problems there. Ran hot lead from + side of battery to coil to bypass ignition, no good.

I should probably state at this point that the system does create spark, but only when switching from 'run' position on the column switch to the 'off' position.

I'm not sure how to test the magnetic pickup in the distributor, but I connected a vohm meter (set to read AC current) to the purple and orange wires on the distributor and cranked the engine. The output was just over 2VAC. I performed the same test on the old distributor by spinning the shaft with a drill and it read 5VAC, but it was spinning much faster than the engine would be while cranking. I also connected the old distributor to the wiring harness (Orange, purple and black wires -->duraspark module), ran ground to the metal housing and spun the shaft on the distributor with the key in the 'run' position. No spark on the test plug that was connected directly to the coil output.

Oh, this is important too: I've never been able to connect the red wire to the duraspark module on my car. If I do it sounds like it wants to start, but will not stay started after it fires. This has been a constant pain in the butt (I just leave it off so I can actually drive the car), and in the course of troubleshooting our current problem I found that there is continuity between that red wire (It's supposed to supply 9VDC to the module while in the run position) and ground. The "I" side of the starter solenoid, which is supposed to supply 12VDC to the module while cranking has never had anything connected to it since I've owned the car. While roaming through the junkyard today I looked at '76 torinos to see how they're wired and none of the ones I saw even had an 'I' post on the starter solenoid so that through me off again.

Whew. Sorry for the lengthy post, if anyone can solve this one for me I'll buy them lunch next time they're in Sacramento. If I don't get this fixed soon my lanlord's going to have this car towed.

Thanks guys,

Shawn

 

My opnion is that your ignition module has an internal short. You should not have continuity between the red wire and ground.

 

Unplug the module. With the key in run, there should be 12 volts on the wire that goes to the red wire in the diagram. If not, you need to fix this.

You can also take the heavy wire off the starter relay that goes to the starter. Then you can spring the keyswitch over to start. You should hear the starter relay "clunk" and you should have 12 volts on the white wire going to the module.

And during both of the above tests, you should have somewhere near 12 volts on the coil positive.