MP Ignition not firing

[SlinktRR]

Check the unit grounds with an ohm meter to battery ground. Do not assume just because everything was clean and tight the ground is good and yes use star washers and bolts if needed for fasteners. If you do not have a good ground it may run but the ECU is going to overheat and melt gound and you do not want that Mopar setting stranded.

This.

Take a voltmeter and go through your ignition wiring, check voltages and grounds. What is the voltage reading at coil positive in "run"? Should be less than 10V or the coil will eventually fail. ECU/coil should not be hot to the touch so soon unless its getting full 12V all the time. Run a ground strap from the ECU to the block.

Bad wiring is a recipe for getting stranded, or worse! I got stranded recently and consider myself lucky I didnt have an electrical fire.

 

[TBass]

ECU is grounded to the block as well as the firewall. The coil did feel hotter than I thought it should after the engine shut off with the new coil. I gotta check the voltage in the "run" position for sure. New coil, ballast, switch. Planning on checking that reluctor gap again. I am pretty certain it is .008". That is what I set it at. I was having an issue with the pickup not being square to the reluctor vanes when I first stuck this new distributor in. The pickup is not an even gap at all. I dunno if that will make this happen, but I also think that if .008" to .010" negatively differentiates things, that the uneven gap would too.

 

[440roadrunner]

My impression, possibly wrong, is that you are throwing more parts at this than you are doing checking

You need to do some checks, and take steps to try to eliminate.

Where is ECU mounted? Too much engine heat?

"New" does not mean "functional" Heat related problems can apply to either coil or ECU but this is typically a "coil fail" problem IE getting hot.

Try to catch it when hot.

Check power TO ignition system, check coil voltage to coil + and ALSO coil NEG

Remove distributor connector, hot, in "run" position of key

Tap the ECU end of the dist. harness connector to ground, that is the bare terminal. The thing should produce a spark each time you do that. If it's quiet and the coil is failing, you might hear a "click" from the system. Clip your meter onto either of the coil terminals and look for a instantaneous change as you "tap" the dist. connector, indicating box is triggering the coil

 

[TBass]

I finally got the chance to dive in with a multimeter. My first obvious concern is the voltage of the charging system overall. Right off the top the battery is showing about 13.85V. The car will fire up and run, but as it is running the voltage will gradually decrease. Once it got down to around 12V it shut off. I went through the entire system after it shut off and that immediately threw a red flag for me. I am now back to thinking it is a charging system issue. While the car was running it gave me proper voltage on both sides of the ballast, at the coil, and the pickup. As of right now, I am leaning toward working through my charging system. As I stated earlier, I have a dual field alternator and the flat can replacement to my old mechanical regulator. Once again, input is welcomed.

I did put my battery charger on it to bring the voltage up again and see if it fires back up.

 

[440roadrunner]

You are telling me that the voltage AT the battery decreases as the car runs? That is strange.

Belt tight?

When it first starts, and is normal (13.8) check both battery voltage and at the alternator output stud, and again when it drops.

Do the "wiggle test" on the VR connector.

Remove the green field wire at the alternator. Ground that disconnected alternator terminal. This will "full field" the alternator. With that in place, check the voltage at the remaining blue field wire, still connected. Should be 'same as battery." Run the engine, bring up RPM and see if voltage increases, keep it under 16V

If that works, I'd replace the VR. Make absolutely certain the VR (and the ECU) are both grounded.

 

[TBass]

In an attempt to do the check you described, I couldn't get it to fire up, so I continued my voltage checks. I broke down and popped the switch out. I started checking the posts on the back and everyone was on deck except IGN2 which is the brown wire going to the ballast resistor. At no point does that post have power according to the multimeter. I may finally have found the culprit. Gotta snatch up a new one. I am definitely gong to check that charging stuff once I get it fired up. Everything I know says it should be at 14.4V when running.

 

[1wild&crazyguy]

sounds like a ballast, but...Is this a matched ignition kit that you are using?
Is the coil using the correct ballast?

I once had an orange box, brand new, plugged it in and it constantly rapid fired the coil and made a electrical whine noise. I pulled it off and wired up an msd6a with same coil and never looked back. The orange box doesn't hold up beyond 6k rpm and 2 out of 5-6 orange boxes were junk right OOTB... they used to be great, I ran those for years on a lot of cars.

opposite end here...but do you have run a non vented gas cap by chance?

 

[TBass]

I bought a Blaster 2 which comes with its own ballast. When I swap coils I swap the ballast accordingly. I also switched from an orange box (made in China) to a chrome box (made in 'murica). Neither swap made a difference.

Never thought about the gas cap. It is the stock cap. 50 years old of course.....

Whatever this gremlin is, it has now developed into a monster. It went from running long enough to actually go on a drive and get me stuck somewhere close to home, to not running long enough to move out of the driveway and back in. I just gotta crack the code. I pick up my new switch tomorrow. If that don't do it, there is no telling where I need to go from there.

It literally just shuts off. As if the key was switched to "OFF". No stumble, no miss, nothing.

 

[SlinktRR]

I bought a Blaster 2 which comes with its own ballast. When I swap coils I swap the ballast accordingly. I also switched from an orange box (made in China) to a chrome box (made in 'murica). Neither swap made a difference.

Never thought about the gas cap. It is the stock cap. 50 years old of course.....

Whatever this gremlin is, it has now developed into a monster. It went from running long enough to actually go on a drive and get me stuck somewhere close to home, to not running long enough to move out of the driveway and back in. I just gotta crack the code. I pick up my new switch tomorrow. If that don't do it, there is no telling where I need to go from there.

It literally just shuts off. As if the key was switched to "OFF". No stumble, no miss, nothing.

Any luck with this one? Post some voltage numbers from the meter if you have them, like before and after the ballast. Also might be worth checking for bad wiring or grounds using voltage drop tests.