ignition issue

[guys71cuda]

vehicle is a 74 w100 318 727 with electronic ignition. when the key is turned to the start position the engine fires then dies immediately when the key is disengaged from start position. the starter is new, the coil is new, the alternator is new, had the battery tested it is good. had the voltage regulator tested it passed. ignition control unit is new. ballast resistor is new. not sure what else to check/replace. any suggestions?

[dodj]

I would double check the 'run' side of the ballast resistor and the wiring connections for it just to be sure then check the ignition switch and make sure there is 12vdc on the 'run' wire. Can't tell you what colour wire to be checking- don't have a print for that vehicle.

[72rtchallenger]

I would double check the 'run' side of the ballast resistor and the wiring connections for it just to be sure then check the ignition switch and make sure there is 12vdc on the 'run' wire.

[guys71cuda]

this is what the resistor wiring looks like . how do i know which side is the run side? the run wire is pink one coming from the bulkhead to resistor correct? i can email u the diagram if it helps

[72rtchallenger]

 When you start turn the ignition key to start, the IGN1 "Run" wire that goes to the ballast resistor (the power for the coil while key is in "run" position) is not hot. Only the full voltage IGN2 "Start" wire that gives extra power to the coil while starting is hot. This is the wire that is connected to the same side of the ballast resistor as the wire that connects to the + terminal on the coil.
I think your run wire is the pink one but cant say for sure.
I would check the ballast ,,just because its new doesnt mean its good,,and make sure you have good connections at the wiring bulkhead

[ShelbyDogg]

The start side has the 2 big wires together under the one female. One comes from the ignition switch (start) position the other wire goes directly to the coil
s + side. That side is working.  You have 12v when in start.   The other wire opposite those 2 is your RUN wire. You should have 12v there when in run position. (usually blue i think)