Ignition Mystery Help please

[Wahoo1]

So this is weird, running a slightly built 383 in my 69 Coronet, new motor, maybe 500 miles on it. New electronic distributor, FBO ignition ECU w/rev limiter and Pertronix flamethrower coil(kit). Starts and runs good but ebery once in a while if driven and shut off won't start again. Not vapor lock just acts like spark dissappears. Always seems to start up again after it sits a while. Coil seems OK, maybe grounding on the ECU not good? Driving me crazy. Any thoughts, I know you guys will have answers, thanks in advance.

 

[451Mopar]

I have had issues like that with bad battery cables.
if it does it again, try jumper cables in parallel with the battery cables.
What I mean is connect one wire of the jumper cable to the battery negative, and the other end to the engine block so it is a parallel circuit.
Try the same with the other lead from the battery positive to the starter battery connection, or at least the the neutral safety relay stud.
I'd also add a ground from the engine block to the firewall/ECU

 

[66Satellite47]

Be sure the ECU has a really good ground.

 

[67 coronet]

first thing to start with is carry a test light with you and check to see if you have power to the coil when this happens. check all the ignition body grounds. scrape off some paint if you are not sure.

 

[lewtot184]

I think i'm having issues with my FBO rev-limiter box. doesn't start good hot and dwell went down to 17 degrees at idle. i'm going to call Don at FBO Monday and see what his take is. always had good luck with FBO, but not so sure about this box.

 

[Wahoo1]

So latest story, added a ground strap from engine block to ecu, fired it up went to gas station fired up again fine. Drove 35 miles to another town stopped for 30 minutes won't start, not even pop. Swapped out ecu from FBO to orange box, nothing, swapped out pertronix cool to accel 12V coil started immediately, only took 15 minutes to do all this. Drove to sisters house 1 mile stopped and bolted new coil down to mount won't start again. Swapped back to FBO ecu and it started. Drove 35 miles home ran great. Stoped engine in drive hit key restarted immediately, waited 15 minutes and it won't start again. Starting to think I'm crazy.

 

[Dennis H]

Easy first. Cables. Does it spin? I say heat-soak ethanol related.

 

[Wahoo1]

Easy first. Cables. Does it spin? I say heat-soak ethanol related.

Spins great, no heat soak on the starter. Fuel in the bowl and squirts when's throttle depressed.

 

[Sixpactogo]

Intermittent issues like the one you are dealing with are a nightmare for sure. It sounds like a bad ground somewhere to me. Bad grounds or bad connections are the most common electrical problems with our old iron. My thoughts are that it could be your coil ground. Does your coil feel hot to the touch after a shut down? Both the coil and the ECU need to have a good ground otherwise with excess current flow can overheat them and they will both open up the internal circuit. Kinda like a circuit breaker and will close back up when they cool down.
If you have a digital Ohm meter, with everything bolted down and hooked up, Check between the case of your coil to Neg on the battery and case of your ECU to Neg on the battery. Should be less than .3 ohms on both to be properly grounded. I can't think of anything else that could open and close the circuitry like you are getting unless it could be the plate coil in the distributor but I have never heard of them healing themselves up. Once they fail, they usually don't come back to life again.

 

[oldbee]

Bulkhead connections? Getting weirder by the minute.

 

[Wahoo1]

Thanks for the thoughts guys, I'll keep trying, testing my limits for sure. I appreciate the help.

 

[miller]

Shot in the dark. Rarely happens, real hard to find.
Somewhere in your wiring circuit, for your ignition, maybe a broke wire. When it's cold/cool, the ends at the break touch, making the circuit. After getting warm, wire expands, opening the break...no contact.
Look over your wiring carefully.

 

[HALIFAXHOPS]

I see this so often with the pick up in the distributor when it gets hot, they have issues new or old see that when I heat them to test them.

 

[451Mopar]

Might be Distrubitor pickup coil, or battery cables (they both can be affected by heat soak.)
Maybe Ballast resistor, but unlikely. Sounds like you swapped out the ECU and coil already

This is what fixed my problem:
http://www.autozone.com/batteries-s...ast-battery-acc-battery-cable/570485_309923_0

 

[Wahoo1]

Might be Distrubitor pickup coil, or battery cables (they both can be affected by heat soak.)
Maybe Ballast resistor, but unlikely. Sounds like you swapped out the ECU and coil already

This is what fixed my problem:
http://www.autozone.com/batteries-s...ast-battery-acc-battery-cable/570485_309923_0

I've got to do some more checking, cables are brand new and motor spins great but I'll check them anyways. Distributor is starting to concern me, replaced rotor, gapping looks good but maybe the pickup.

 

[demonram]

I know you replaced the coil. Just for kicks try another one, I had the same issue. I replaced the coil, never had that issue again. It's worth a shot.

 

[67 coronet]

might be a good idea to go through and shake all the wiring in the eng compartment and under dash while at idle. if it stalls or hesitates then you have an area to check for bad connection. if nothing, then you at least know its not a loose connection.