72 challenger 340 no spark issue!

the listed nominal spec on a 4 terminal ballast is 5 ohms on one side and .5 ohms on the other side. It's confusing because you think the .5 ohms (less resistance = more flow) would be the start side and 5 ohms would be the run side(for the coil) but the .5 ohm side is the "run" side(to the coil)which is a correct amount of resistance & as you know the ballast is bypassed completely to the coil for "start". This leaves the 5 ohm side of the ballast which is used for the extra "start" side circuit for the ECU (5 pin only) not the coil. Both the 4 and 5 pin ECU's get running voltage from the blue (ign 1 run) circuit. The 5 pin ECU has 2 circuits, the 5 ohm for starting and the above (ign 1) for running voltage. A spare I have shows 6 ohms from upper left to lower left and 1.4 ohms from upper right to lower right. Lower left has a blue lead switched 12V(ign 1) to it and it jumps across to the lower right with a short blue loop. Upper right is a heavy brown wire which goes to the coil positive pri terminal. The upper left is a green w a red tracer which goes to the ECU connector. The archives state that this green w red tracer wire is not used w a 4 pin ECU AND a 2 terminal ballast but in the factory shop manuals the green w red tracer wire is used with a 5 pin ECU and a 4 terminal ballast. That's what I have so far.

Ok thanks!So In my picture I have juice on both bottom terminals when key is on.If I am following u correctly i should only have juice on one side of the bottom of the resistor? I am going back tuesday to my brothers I will check that.. also I talked to him tonight and he said its got a 4 pin harness and a 4 pin module.. it was his 72 charger that has the 5 pin one sorry.. but your description of wire colors sounds right from what i have seen on his. will verify tho tuesday

I reread everything and you have a 4 pin ECU w the (pictured) 4 terminal (dual) ballast, correct? If so (1) see if you have continuity between the upper right and lower right terminals (disconnect both plugs & ohm it if you have a VOM) (2) see that the upper right (brown) terminal has fire when "cranking" & on to the coil positive pri terminal (3) that the "point" of the ECU pentastar connector has fire in "crank".

Yes that is correct From what he told me.. also when u say terminals do u mean the plugs on the harness for continuity? or on the ballast? with key on or in start mode? and am I checking for voltage at the pos primary at the sametime in crank mode? Just ground my neg meter wire while checking it? should i disconnect brown wire on relay so i don't turn motor over while checking this?

ok I am here now and i checked ballast it ohms out. then i checked for fire at hot side and crank side and i have voltage and then i checked for fire at pos side coil in crank and I have fire around 11 volts then i checked at the pentastar and with key on it has around 8 volts go into crank mode and it drops to 3.50 volts or less... so whats going on? where would i be loosing that voltage? where do trace from now? I also looked and it has the 5 pin harness with 4 pin ECU and dual ballast

jump 12V directly from the battery positive over to the "point" of the pentastar & crank it & see if starts then we'll work upstream on that circuit to find the bad connection. EDIT has it ever ran wired up the way it is right now? Just making sure we have it wired correct.

I hope your sitting down when u read this ,lol... yes it did run, but we HAVE had other issues with worn timing chain, bad dist, bad dist gear etc and then this now surfaces!,Here is what i found tonight! the pos brown wire was on the wrong side of coil! then i switched that so it was right and checked again same voltage drop!.. then i started to look into the bulk head.And man what I found is just plain unbelievable! someone spliced into the yellow ignition wire on engine side bulkhead and ran that to the ignition on relay and also to the brake light switch below master cylinder! that wire was all melted inside the tape! also the red heavy wire that goes to relay they just ran it thru the damn bulkhead where the connector should have been and spliced into the red on the other side!.So where do i go from here? and do u think this was the problem? How did it even run the other way with the crappy gear ,dist,chain eyt is way beyond me!! I will post a pic later

Yes I am sitting down as that expends the least amt of energy. Well we're making progress. One (system) at a time. www.mymopar.com has factory wiring diagrams, go to mymopar tools/reference in the main menu on the left then click wiring/electrical. It helped me immensely rewiring my 65 Dart. Holler back when you can

Here's a pic of the harness and what I marked how it was

I'd cut the splices & go back to basics & run the ign 1(run) out to the ballast upstream side(the blue loop) and to the point of the pentastar and ign 2(crank)out to the yellow solenoid wire.

could u show or draw me what your talking about?
thanks!

Go onto the "tech archives" at the top of the page then click on "electrical topics" then click on "awesome ecu wiring diagram" & they have a comprehensive schematic that will help you better than I can explain it but the yellow wire on the diagram is wrong, you run that yellow wire from the (st) terminal on the ign sw out to the starter relay and it does not connect to the ballast.

So Is that the same yellow that is all melted coming out of my harness bulkhead then? just make a new one off that connector and reconnect to ign terminal on relay where it was?

How do u get the old terminal out of bulkhead? I have a extra harness from a 74 challenger and will just use that yellow wire..thanks!

on the male terminals one end will compress & one wont & you slightly compress the one that will move just slightly then it will come out the back side easily. The female ones look at the rectangular hole and on one side there is a mini groove & use an eyeglass screwdriver to go in & depress the tab then pull it out the back side also.

Thank you! I will give it a shot saturday...

well went back and worked on the car and I got it running but I found some cluster crap in harness, and I have included a pic of what someone did.. can u guys take a look and see what they did is ok? tx! Its running ,but need to tweak rotor placement etc now and then go from there..

here is the power acc relay? that the one blue wire goes back to from previous pic.

No opinions on the above pics?

Swap in a known good working distributor. My friends 440 was doing the same exact thing. The Pickup in his reman distributor came loose.

I have that same wiring diagram at my brother's ,but its not clear on the wiring for the ign module? it only shows 3 wires? and two of them are going to something i never heard of speed switch? whats that?

well Haven't had a chance to get back to it.. Maybe this week sometime

We'll I think this Damn thing is useless at this point! it still will not run very well! I have it at 30 initial now just so it will run! Unknown on cam specs etc, And to top it off there is a damn knock somewhere in this motor! its towards the center sounds like? it doesnt go away when u rev it a little, i pulled all but the last two plug wires on drivers side as there a bitc* with headers and it didnt go away. so thinking no rod bearing. could be a main? or what else do u guys think? this motor was suppose to have been all rebuilt too! But after everything i have seen so far with the seller i wouldn't doubt he put used fricken bearings back in!! also when i pulled the drivers side valve cover to make sure both valves were closed At TDC I seen this on a couple of pushrods. this is the worse one u can literally feel a nice deep groove in it! where did that come from? I watched it roll over and it doesn't even come close to hitting way up ther ein the pushrod hole. Also how close should the pushrod be when valve is closed to that hole? cause its very close!
p.s Is there anyone close to me that can come look at this for me? thanks!!

Is there anyone close by that can stop by and listen to this car to help me decide what I need to do?