73 Challenger w 318 4 bbl Holley no spark

[rbaudanza]

I have a 73 Challenger with a 318 engine that has been sitting for some years, maybe like 5. I changed battery drained out fuel, car will turn over but I can't seem to get any spark. It looks like the original ignition was swapped at some point. There is a 4 prong ballast resistor, stock looking coil, and what appears to be a ready to run or HEI type accel distributor in it. With key on I get 12 volts into ballast resister and 10 - 11 volts at the coil positive, when I crank the voltage at the positive goes down to like 6 or so. Not sure where else to go from here, already changed plugs, wires, cap, rotor, coil, and ballast resistor before I started taking voltage readings because they were old, not that expensive to do, and going to need to be changed anyways since the car was sitting so long. I was hoping changing them would give me some spark but no luck. If anyone can help me where to go from here, I'm figuring testing the distributor is next I'm just not sure how to do that. Any help I can get would be greatly appreciated!

By the way most of what I have done to this point is the result of trolling the internet and using my rudimentary engine knowledge so please forgive any misinformation I may be giving above. I'm also dreading if I have to change the distributor as I have never attempted that before.

 

[66plyValiant]

is it still running a mopar 4 pin ECU or is the distributor a ready to run unit?

 

[67Dart273]

If the coil + voltage drops that far when cranking, the ballast resistor bypass circuit is not active.

Basically what you "had" in the Mopar 4 terminal resistor is TWO separate resistors in one ceramic block

One resistor fed the coil + just like a "points" system, and in fact was very close or the same resistance.

So for that "half" of the resistor, you have:

1---IGN 1 or "ignition run" traditionally dark blue. (I didn't look at a diagram of a 73, might be different color) This "run" voltage is hot ONLY when the key is in the "run" position.

So in "start" you need something "else" to provide start power

There are two OTHER SEPARATE switch contacts inside your ignition "switch" which in reality is SEVERAL switches in the same housing.

2--One is the yellow "start" wire which is working because the engine will crank.

3--The last is known by Ma as "IGN 2" and is the "bypass" circuit. This is a separate switch contact, feeds a traditionally brown wire through the bulkhead/ firewall connector, and goes to the coil + side of the ballast resistor. THIS IS hot ONLY in "start" and is the ONLY source of ignition voltage during "start" or "cranking."

So look at your ballast / harness and see if that brown, coming out of the bulkhead, is hooked up. If so, probe the firewall connector. Wiggle the harness connector vigorously and see if it comes alive. If you cannot "find" power on that wire, get under the column at the ignition switch connector and see if you have power on that wire in "crank." Refer to a proper year/ model diagram to be sure you have the right color.

I have a 74 manual, not certain if it's correct.

 

[rbaudanza]

is it still running a mopar 4 pin ECU or is the distributor a ready to run unit?

It is not running the 4 pin ECU. I assume it's a ready to run distributor but I'm not really an expert. I came to that assumption after searching for the darn ECU and never finding it, then while using google to search for was to test the distributor and pickup coming across people talking about using HEI modules in Mopar ignitions. When I looked at the distributor in the car I noticed the pickup was connected to what looked like an HEI module attached directly to the bottom of the distributor and wired the same way posts were explaining witring in HEI modules. I then came accross the ready to run type distributors and putting 2 and 2 together assume this is what I have installed. I'm assuming a ready to run distributor really just a distributor with an HEI module installed in it.

If the coil + voltage drops that far when cranking, the ballast resistor bypass circuit is not active.

Basically what you "had" in the Mopar 4 terminal resistor is TWO separate resistors in one ceramic block

One resistor fed the coil + just like a "points" system, and in fact was very close or the same resistance.

So for that "half" of the resistor, you have:

1---IGN 1 or "ignition run" traditionally dark blue. (I didn't look at a diagram of a 73, might be different color) This "run" voltage is hot ONLY when the key is in the "run" position.

So in "start" you need something "else" to provide start power

There are two OTHER SEPARATE switch contacts inside your ignition "switch" which in reality is SEVERAL switches in the same housing.

2--One is the yellow "start" wire which is working because the engine will crank.

3--The last is known by Ma as "IGN 2" and is the "bypass" circuit. This is a separate switch contact, feeds a traditionally brown wire through the bulkhead/ firewall connector, and goes to the coil + side of the ballast resistor. THIS IS hot ONLY in "start" and is the ONLY source of ignition voltage during "start" or "cranking."

So look at your ballast / harness and see if that brown, coming out of the bulkhead, is hooked up. If so, probe the firewall connector. Wiggle the harness connector vigorously and see if it comes alive. If you cannot "find" power on that wire, get under the column at the ignition switch connector and see if you have power on that wire in "crank." Refer to a proper year/ model diagram to be sure you have the right color.

I have a 74 manual, not certain if it's correct.

AHHHHHHHH, thank you this is a big help. I noticed there is some rot on the firewall around where the connectors are so could be the issue. I have been using the wiring diagram I found at this link http://www.mymopar.com/downloads/1973/73ChallengerA.JPG looks like connector 22 on the fw connection is where I need to test. I will let you know as soon as I can test this. Hopefully tonight.

Thank you both for responding.