[71_challenger]

Great forum that you guys have here. I found it whiel trying to research my lack of spark problem that I have on my 71 Challenger.

A little history first. I bought the car about 2 years ago with the orignial 340 4-barrel and 727 torqueflite. I drove the car for about 3-4 months while suffering through 4 blown head gaskets and a slipping tranny. I had the heads redone with new valves, new 3 angle valve job, new comp cams springs, guides, etc. and they required approximately .008in machined off to be flat. So, after all this, I parked the car, and tore into the engine to find the answer to the problems. I believe that it was overheated repeatedly some where in its previous life. The engine need to be bored, decked, mains honed, etc. Lots of machine work and money so, I put it aside for a while. About a year later, I got a lead on a 76 Chrysler New Yorker with a 440 and 727 that I could have for $25 if I got the car out of the field and took it away. What a deal it seemed like. Long story short on the 440 is that after going through the machine shop and being checked, the only machine work required was a new valve job on the heads. And, the tranny check out as good as well. So, I decided why not go with the no replacement for displacement attitude and to save my original drive train I decided to convert to a 440.

OK, I now have the engine installed and all the wiring put back in and ready to fire it up. Here is my problem. The engine will turn over, but I am not getting any spark to the plugs. The distributor is a new Mopar Performance unit, new Taylor Ignition wires, new spark plugs, and new battery (I keep it charged using a trickle charger overnight). I had previously converted the 340 setup to the Mopar Electronic ignition setup with the orange box (which was all working when I parked it). Before reinstalling the wiring, I did a continuity check on all the engine and dash harnesses to verify they were good. I have traced the starting wires and have found the following:
1) Dark Blue wire with white tracer gets 12V in the run position at the ballast resistor
2) The Brown wires going to the other side of the ballast resistor and the coil are receiving approximately 9-9.5V in the start position.
3) It has an Accel 8140 Super Coil (came with the car) I have measured the primary resistance to be 1.5 ohms and secondary resistance of 7.2 kohms.
4) I have checked the ignition coil wire and it seems to be OK. I even changed to the old coil wire that came off of the running 340 and no difference.

In the start position, should there be more than 9-9.5V going to the coil? If this is correct, then it has to be the coil, right?

Thanks for the help and the great message board.

[papasan]

Have you check the ballast resistor located on the firewall? If this resistor breaks, often times there will be no spark to the coil.

[dave-r]

You should get full battery voltage to the coil +ve with the ignition in the "start" position and around 10 volts in the "run" position (through the resistor).

Have you got the orange box connected up right?

The black/yellow wire goes to the -ve of the coil. The blue/yellow wire goes to the "run" side of the resistor.

[dave-r]

Oh. And this thread should be in the "Electrical" section. I will move it later.

Have a look through that section. There is a lot of these sort of problems in there.

[dave-r]

A normal "factory" coil primary winding resistance should only be about one ohm. Yours sounds OK to me.

The secondary winding resistance should be somewhere between 4,000 and 10,000 ohms.

Again. Yours seems OK.

[71_challenger]

Thanks guys for the insight and help. I found the problem this afternoon. It turned out to be that the coil was being grounded through the choke ground. Oops. Changed the wiring to correct that and SPARK! Almost fired before dinner. I think I need to adjust the timing a bit before trying any more. Tomorrow will be a good day. Thanks again and here are a couple of pictures from about a year ago.