Hi every one. i have a 77 f100 that seems to have ignition problems and im out of ideas as to what it could be. a little background on the truck it has a 300 l6 3 speed manual with a draw through turbo setup. on the trucks maiden voyage with the turbo it made it about 5 miles and then just shut off. no sputtering or surging just died. so i checked for spark and nothing. thinking the coil had gone bad i threw in a spare and nothing. also tried installing a spare igniter box and ignition switch with no luck. so i bought an hei distributor thinking maybe the pickup in the distributor had gone out and to eliminate the igniter box and external coil. after the install the truck fired and ran better than ever. even fixed a fequent missfire at idle, but it would shut off after a couple of minutes. so i checked the charging system and the alternator output was at 12.5 volts, so i replaced the alternator and regulator. after that once again the truck ran fine except now it ran for much longer. however if you try and move the truck it immediately dies and wont restart. i checked for spark and nothing. so i checked incoming voltage to the distributor and it was at 5 volts. to circumvent the factory wiring harness i installed a toggle switch to provide power to the distributor strait from the battery. after that i got my spark back and the truck fired but the same problem occurs. try and move it and it dies as soon as the clutch begins to grab, and then no spark from the distributor but now i know it has 12 volts to the coil. so i replaced the coil in the distributor thinking maybe it was bad and nothing new. if you let the truck sit for an hour or so there is a good chance it will fire back up but i have never had a coil overheat that fast in any of my chevys. i have checked and cleaned the grounds from the battery to the motor and from the motor to the cab. i have also swapped out the battery for the one in my brothers f150 with the same results. any ideas? sorry for the long post just trying to provide as much info as i can

 

Ignition switch could be causing it maybe, or wiring.

 

The OE coil and dizzy module were voltage 'matched' by way of a resistor wire.

The new HEI already has the module and coil matched, so using the OE resistor wire will drop the voltage, although 5V sounds very low.

Remove your entire OE coil wiring and toggle switch, and replace it with brand new 12 gauge wire.

Not sure why the coil is overheating !?

Is the charging system putting out 14+ volts with the engine running ?

If yes, then 12v to the coil is too low, but should not cause the engine to cut out.

 

Missing an engine ground?? Sounds electrical,,

 

Sounds like the ignition module, my truck would die randomly but start and run if i let it sit awhile

 

I'm wondering if your "igniter box" is the same as the ignition control module. As mentioned, the ICM can cause intermittent difficulties as you described, but if you already changed it, it would be unlikely that both would produce the same results. Watch for bad connections resulting in low or no voltage. Intermittent problems can be exasperating. Best wishes.

 

So it's an HEI? I wonder if you burned up the internal module when running it on the 5 volts from the resistor wire. HEIs definitely need the full 12 volts.