Troubleshooting help - Crank but no start

[GregD]

Good morning,
I'm looking for some troubleshooting tips to help determine why my 1971 Challenger 440 6 pack/automatic will not start. Some background on the issue. The car was starting and running fine. While on a drive last weekend, the car randomly shut off while driving about 25-30 mph. There was no stumble or hesitation at all. It just turned off as if someone turned off the key. I pulled over and it fired right back up without issue. I continued on my drive of about 10 miles. Later on that night, it fired up without issue and I drove about 15 miles home. The following day, I went to start it and it would fire up, but as soon as I released the key from the start position, it would die right away. I suspected a fault ballast resistor. I ran a jumper wire from the positive battery terminal to the positive post on the coil. The car fired right up and stayed running even after releasing the key. In order to turn off the car, I removed the negative battery cable. The car was running for approx 3 mins before i shut it down with the neg battery cable. I removed the jumper wire and then picked up a new ballast resistor. I installed the new one and attempted to start the car. it would crank, but not start at all. I reinstalled the jumper wire and still it would crank and no start. I installed the old ballast resistor and still it will crank but no start. Any tips for troubleshooting this?
thanks,
Greg

 

[Deathproofcuda]

Roadside Troubleshooting

 

[Deathproofcuda]

Points or electronic ignition? Running your car with the jumper wire may have damaged the points or ECU.

I would start by checking cranking voltage at the positive side of the coil.

 

[Chryco Psycho]

Replace the ballast resister

 

[GregD]

Points or electronic ignition? Running your car with the jumper wire may have damaged the points or ECU.

I would start by checking cranking voltage at the positive side of the coil.

electronic ignition. I had replaced the ECU recently, within the last two years. If no cranking voltage, do you think i damaged the ecu?

 

[GregD]

Replace the ballast resister

That was the first step i took to try to fix the original issue. but now the car won't start at all with the old resistor or the new one.

 

[Chryco Psycho]

Did you try jumping it with no ballast ?

 

[oneof52]

Where is your coil located? If its on the intake manifold, move it to the fender, even if for troubleshooting. I had a similar problem, and when the engine got hot, would short the coil and leak oil. Moved it to the fender, no more problems. Air, Fuel, Spark.....

 

[GregD]

Did you try jumping it with no ballast ?

no, i didn't. do i just unplug the two plugs from the ballast and leave disconnected? then run the jumper wire like i did before?

 

[GregD]

Where is your coil located? If its on the intake manifold, move it to the fender, even if for troubleshooting. I had a similar problem, and when the engine got hot, would short the coil and leak oil. Moved it to the fender, no more problems. Air, Fuel, Spark.....

its on the intake. engine is cold and will not start. but maybe the heat got to the coil and its dead?

 

[Chryco Psycho]

try that

 

[oneof52]

Try another coil. When it overheats, oil leaks and no insulator between primary and secondary - it’s a quick check. Continuity check center to positive. Meter beeps, got a short in the coil

 

[Deathproofcuda]

electronic ignition. I had replaced the ECU recently, within the last two years. If no cranking voltage, do you think i damaged the ecu?

Actually, scrap the cranking voltage test. You already ran a jumper from the battery directly to the coil and it didn't start, so your problem is at the coil or downstream. So if no spark is your issue, then its either the coil, ECU or the distributor. I know this started as an ignition issue, but just to be certain, have you confirmed that the carb is getting fuel?

 

[Chryco Psycho]

If you connect & disconnect ground at the coil with the power on the coil should spark everytime the ground is disconnected

 

[GregD]

Try another coil. When it overheats, oil leaks and no insulator between primary and secondary - it’s a quick check. Continuity check center to positive. Meter beeps, got a short in the coil

did a quick swap out to a Blaster2 coil i had lying around. no difference

 

[GregD]

Actually, scrap the cranking voltage test. You already ran a jumper from the battery directly to the coil and it didn't start, so your problem is at the coil or downstream. So if no spark is your issue, then its either the coil, ECU or the distributor. I know this started as an ignition issue, but just to be certain, have you confirmed that the carb is getting fuel?

sprayed in some starter fluid to rule out fuel as as an issue. no difference.

 

[GregD]

starting to think the ECU took a dump even though its very new. I ordered a new one. I'll keep it as a spare if that doesn't end up being the issue.

 

[Deathproofcuda]

starting to think the ECU took a dump even though its very new. I ordered a new one. I'll keep it as a spare if that doesn't end up being the issue.

I think you're probably right. My understanding is that the newer ECUs take dumps on a fairly frequent basis, so carrying a spare is recommended. Part of the reason why I'm still running points.

 

[Ricks72Chlgr440]

I highly recommend going to the FBO ignition setup. Their ECU is top notch, and when purchased with the flamethrower coil you can bypass the ballast entirely. As a bonus, their ECU has a built in rev limiter as well.

FBO Ignition Systems MOPAR Micro-Processor IGNITION SYSTEMS Digital Micro Processor Circuitry|EPROM Processor with|Built in DEAD STOP Algorithm REV Limiter|Eliminates Ballast Resistor|44KV Output on demand|Plug and Play|one simple wiring modification

 

[Chryco Psycho]

I highly recommend NOT using FBO junk , all the systems I sold either filed or created far worse performance , even a $15 ECU works better . Their return policy is just as bad if you have a problem return it right ? Nope they say it works fine & do not refund .