Cranking Issues

[CornDogsCharger]

Working on a 1970 Coronet RT, 440 4bbl, 4spd. Someone already converted it over to electronic ignition. We rebuilt the engine, rebuilt suspension, painted and fully detailed the engine compartment. In doing so, we installed a new "modified" engine harness from M&H where the electronic connectors are included with the regular harness. We also replaced the ECU module, ballast, starter relay, coil, and ignition switch with all brand new BWD parts. The electronic distributor is new from Chrysler. Now, the issue. When you remove the coil wire and crank it, the only time you see a spark is whenyou release the key in the crank position. Usually it will only spark once. Everything is grounded and I'm just about out of ideas on what it could be. Any help would be greatly appreciated.
Justin
"CornDog"

[Nacho-RT74]

If we are sure everything is new, I would bet a loosen contact around... ECU plug, Dist plug, or ballast plug.

NOW, have you check down the dash for loosen terminals on bulkhead ? You could push it out when conecting the new harness plug. Check specially the blue and brown wires that cames from ign switch up to bulkhead

Have you tried feed the ballast directly from batt and crank it ?

[macca3441]

Hi mate,

It sounds as though the ballast by-pass (the wire that by-passes the ballast resistor and powers the coil while cranking) is either not wired in, or open-circuit!
Therefore, with the key in the "start" position, the coil has no power, and as you're releasing the key, you're momentarily giving the coil its normal ignition power through the resistor!
Hope this helps...


Wade

[CornDogsCharger]

I will check all of the connections again and make sure everything is like it should be. Wade, if what you say is the case, how would you go about fixing the problem. Do you think it could be a faulty new part? Possibly the harness too?  Thanks for the help.
Justin
"CornDog"

[macca3441]

Justin, the problem may lie in the new harness! Or, it may not!
Hard to diagnose over a computer!
Something to try..... With a test light, probe the +ve side of the coil. Turn on your ignition, and the test light lights up!
Continue to hold test light on +ve side of coil, and turn the key to crank. This is when you'll lose power??? Am I right??  If so, then it's a by-pass problem!
This can be solved in a couple of ways, however, (if it was me) I'd want the fault found and fixed!
You'll have to trace this wire back through the harness, probing with your test light along the way, testing for crank power at each connection, plug, relay, switch, etc... that this wire runs through!
I'm not sure whether the harness you have gets it's ballast by-pass from the ignition switch, or starter relay, or somewhere else. You'll have to trace that wire back to find out!

Wade

[68charger440R/T]

I had the same problem, I replaced the ballast resistor and it fired right up.