ecu and/or ballast resistor causing dead short at key
 

i have a 1970 plymouth gtx. bought the car rolling with no drive train. put a 1966 440 in it. bought electronic conversion kit ( which contains distributor, ballast and ecu box ). purchased an engine harness from year one already converted for electronic application. harness came to accommodate 4 prong ballast resistor. by going this way i figured i'd make my life easier, just plug everything in. not so. engine turns and starts from starter relay. dead at key. no click, nothing. unplug ballast and it turns with key or remove ecu from firewall taking away the ground and it also turns over with the key. when everything is mounted i believe a dead short is being caused. HELP PLEASE!!

Sounds more like the ballast is wired wrong

Check back of ballast, if it is open back type with exposed coil see if broken and touching firewall.

440 -

Check / replace the ballast resistor and it's wiring. Even if that's not it, you will want a spare in the glove box. They really don't go all that often, but when they do, you'll need one usually in a hurry.

Archer

i've tried 3 ballast resistors which are all good. have the new ecu box that came with the kit plus 2 others i've tried. it's something with the wires i'm sure. i think things get a little more complicated when using the 4 prong ballast. the ecu box has 5 wire connections but in actual fact only 4 of those connections are in the current. i've also heard that there are ecu's which actually do use all 5 connections. i went this route so i wouldn't have to mess around with wires ( lol ). i would like to know how to modify this for a 2 prong ballast.

Here is some info and a 2 prong diagram.

http://www.mopar1.us/electronic.html

4 and 5 pin drawing.

http://www.allpar.com/fix/electronic-ignition.html

sweet, thanks for the links. i'm sure this will help me. i'll let you know how i make out

Please do. I prefer passing along info rather than telling someone what to do. Good Luck.

Coronet 500s post showing allpar is the best diagrams. hint which ever ballast you have get 2 new ones, put them in your glove box. on the first "no start" just replace the one under the hood. i bet that will fix it. it will happen in the cold or heat most likely. HINT to test the coil in the distributor. 1. get an analog meter. 2. set it on the lowest AC setting. 3. unplug the dist wires. 4. put the meter wires into the dist wires. 5. spin the dist, the faster the better. 6 if the coil is set right and the coil it self is good. and the meter wiggles the dist is good. it wont move much.

This sounds to me more like your harness is wired incorrectly, and that the ballast might be loading an incorrectly wired situation

First, it's helpful to understand how Mopar ignition switches work from the early sixties into the ?? 80's

You of course have SEVERAL switch contacts inside the can that we call the "ignition switch." ALL of these contacts act as separate switches

1---Accessory, not relevant to this problem, is HOT in run or acc, feeds power to the switched buss in the fuse box

2--Ign 1, or "ignition run" traditionally dark blue (different in some late vehicles) is hot ONLY in run and feeds power to the switch side of the ballast, to the regulator IGN terminal, to alternator field 70/ later cars, and to a couple of smog doo-dads on late cars HOT ONLY IN RUN, NOT hot in "start"

3--Start, traditionally yellow, goes directly from the switch, through the bulkhead connector, to one of the push--on connectors on the start relay EXCEPT in cars with the dreaded seat belt interlock, where it is routed in series with the reset device under the hood. HOT only in start, this operates the start relay

4--IGN2, or bypass, traditionally brown is yet another set of contacts in the switch, goes from the switch, directly through the bulkhead connector, and to the coil + side of the ballast resistor. HOT only in start. THIS IS the ONLY source of ignition voltage during "crank" or "start."