1973 Dodge Charger 400 Ignition... issues...

[MoparMilitia]

Hi All, Brand new here. Im sorry if this post gets long, but I'm going to try and supply as much information as I possibly can to try and get some help here.. so lets start with..
1973 Dodge Charger Base
400 6.6L Stock Big Block. no heads, no cams, no intake.
FiTech EFI Fuel Injection system (hpgo 400hp)
Hedman Long tube headers

now to the issues..

I was driving the car out to a job one day for about 45 minutes. toward the end of my ride I started to hear kind of a drone from the motor at higher RPM. first gear, second gear, third gear all sounded great under medium throttle. But, as id get up to 55mph, where you kind of feather the throttle to maintain speed, for the split second I would let off the pedal just a hair, I would get what I can only describe as a droning misfire (kinda sounded like a Subaru boxer motor which made me really angry lol) but anyways, didn't think much of it. car kept doing as described and eventually just transformed into a complete total running like crap misfire. after looking at the previous owners hack job install of the fitech system, I decided to take a peek under the distributor to see what his version of "upgrading" to electronic ignition looked like. Lifted the cap and found a pretronix points to electronic conversion kit. read around on the forums and saw people had mixed feelings about them so on a whim, I replaced thee entire distributor with a Proform from summit racing. still didn't fix my issues. so I replaced, and rewired per Mopars diagram the Ignition module (blue box), ballast resistor, ignition coil, spark plugs with NGK's and the plug wires with MSD's. Car did run noticeably better, but still missing. to the point where under any form of load, car sputters, backfires.. but never stalls. a friend of mine showed me a trick to ground a test light, and probe the spark plug wires on the distributor to see if you hear a noticeable change in rpm at idle. all cylinders checked out BESIDES cyl 8 and 3. So... with my stomach in my throat I compression test ALL cylinders. Every Cylinder has between 130-145 psi of compression. so I was pretty relieved there. Then, I went and bought a HEI spark tester ( the little thing that looks just like a spark plug with a ground clamp) and I hooked it up to cylinder 8. Fired the car up and this is where its making me pull my hair out. Spark no spark, no spark, spark, no spark. intermittently cutting in and out. pulled the wire off the distributor and held it close to the post on the distributor and got constant, blue crisp loud cracking spark. hooked up the plug wire and then still same thing on the spark plug end of the cable. so I thought, ok maybe the plug wires bad. I've tried 6 or 7 different plug wires all with the same result.. car idling along, misfiring and still have intermittent spark on the spark tester.

so... any clues? I've tried new plugs, wires, ignition module, 4 pin ballast resistor and 3 different coils all with the same result. The only thing I can describe this weird INTERMITTENT loss of spark is that the spark is just weak. but after replacing ALL of the ignition parts, still no avail.

Thank you all very much for enduring that long winded plea for help, and also thanks in advance for anyone who replies.

 

[MoparMilitia]

Update : it’s 1am now, so thank you to anyone who replies overnight. Tomorrow during the day I’m going to try and take a video and get it up on YouTube to share with you guys showing you my wiring and everything. Thanks again, goodnight all!

 

[MoparLeo]

Instead of throwing hail Mary's at it (which can get expen$ive) do you have a good repair shop in the area that can do proper testing on it ? I had a saying in my shop for my techs which reads " Do what you do, don't do what you don't do" In other words know when it is above your head and then find someone who knows what they are doing.

 

[MoparMilitia]

Instead of throwing hail Mary's at it (which can get expen$ive) do you have a good repair shop in the area that can do proper testing on it ? I had a saying in my shop for my techs which reads " Do what you do, don't do what you don't do" In other words know when it is above your head and then find someone who knows what they are doing.

I didn’t really see it as “busting out the parts cannon” lol because everything that was in there was cobbled together to begin with so I figured replace it anyways. I think I’m into it $250..$300? I just bought the car a few months back, and just wanna drive the thing.

 

[400sforever]

Is there a chance the timing could be off? I had a charger do something similar, although it was all stock, and found the timing to be off

 

[MoparMilitia]

Thanks for the reply! Have the timing set right, did it about 10° with a light on cyl one. Like I said the only thing I can’t wrap my head around is how the spark tester would fire, fire, not fire, fire fire fire. Not fire. It’s just a weird intermittent loss of spark, yet if I hold a test light near the center of the tester it gets strong blue spark. Just seems weak to me like it just doesn’t have the juice to just the gap at all times

 

[steve340]

Is it something to do with the fuel pump or Fitech system.
Low fuel pressure could be causing a lean misfire which is red herring you in to thinking it is ignition related.

 

[MoparMilitia]

Is it something to do with the fuel pump or Fitech system.
Low fuel pressure could be causing a lean misfire which is red herring you in to thinking it is ignition related.

Thanks for the reply! And Honestly the only tool I don’t seem to have is a fuel pressure gauge. I don’t really think it’s fuel related, as I just replaced all the fuel line, pump and filter to swap back to a return line system when I first got it, and also when it’s missing the car reaks of raw fuel, as well as if it were something such as a clogged injector I would think the fault code section of the EFI’s handheld would catch it as it catches almost every little thing. I could be wrong though, suppose a trip to harbor freight to grab a gauge wouldn’t hurt.

 

[WP29440SE]

I'll take a shot here. first make sure all your engine grounds are good , metal on metal, second, your ignition box must be thoroughly grounded to the firewall. if you have a dual ballast, make sure the plugs are in their proper positions with the tabs in their holes and no broken. if you now have an electronic pickup in the distributor, that gap needs to be .008. make sure your ballast is putting out adequate run voltage, around 9 volts with Mopar electronic ignition. I eliminated the standard Mopar box and ballast using a GM module to get 12 v full time volts to the coil. make sure your coil is actually putting out adequate voltage. you might as well check your charging output to the battery, 13.8 to 14.2 volts. timing could be something, but where you have it set , I doubt that's an issue because it would most likely be across all cylinders.