So I've been lurking around here for awhile but this problem really has me stumped.

My 79 F250 400M won't start at all now. Originally started out not starting when hot. So I replaced the ignition control module. Wouldn't start hot. New coil. Still wouldn't start hot. Would run for about 15 min and then shut off like somebody turned the key off. Let it sit for awhile (30 min to 2 hrs) and it'd fire up. Got it home and went to replacing plugs and wires (was due anyway) and since it died from getting it home it won't start at all. Cranks and cranks and cranks. There is power (6+ volts) to the coil with key on. Don't have a volt meter to get an exact number. There's no spark coming outta the coil (new or old. Hooked both up to try). Put a new distributor in. Still cranks and cranks and cranks. I'm stumped now and not sure what my next step is. Any help is appreciated.

 

Have you checked to see if the dist rotor is turning when the engine cranks?

 

How do you know you have 6 volts to the coil if you don't have a voltmeter? Whether you have 6 volts or 12 volts matters. 6 volts means the module is grounding the coil like it should. 12 volts means the coil is floating. Both will light up a test light.

 

Dist turns when cranking

Just have a basic wire tester. Has lights for 6v, 12v, 13v, and 24v. Checks voltage and continuity.

 

I'd go ahead and grab a multimeter to get real numbers. I wouldn't rely on something like that. You're going to need a multimeter to measure the pickup coil resistance anyway. How are you checking for spark?

 

Been using one of the old spark plugs I took out.

 

That doesn't exactly answer the question. Please explain how you're checking for spark, in complete detail, including what actually cranks the engine.

 

Key is on
Use a jumper wire on the solenoid to turn the engine over
Hold the wire with the old spark plug close to something metal and watch for spark.

 

Thanks, that sounds good (sometimes folks report no spark when in fact they didn't leave the key on first). Sounds like you're on the right track.

Next I would borrow or pick up a cheap multimeter and double check the coil voltage with the key in RUN to make sure the module can actually ground the coil. If that checks out, move on to check the pickup coil resistance.

 

Well I feel like an idiot.

Buddy came over after work and we started going through double checking everything. Found a bad wire going to the coil. Fixed that. Then found in my haste putting new distributor in I didn't swap the rotor to match the cap. Came with 2 styles of caps.

 

Glad to hear you got it worked out. We've all been there.