47-55.1 49 GMC 100 5.3 swap engine only runs in start position

[skymangs]

I’m using an aftermarket harness. Sounds great until you let off the key, then it dies. Bought a new Ignition switch last night, we’ll see what that does. I’m at my wits end! Any ideas would be appreciated.

[joedoh]

what ignition switch are you using? some have two "coil ign" terminals, one through a ballast resistor and one that gives full voltage for starting, and it switches between them when you cycle to the start. a new switch would probably fix this.

other than that, make sure you have hots to hot and ign to ign and accy to accy. i seem to remember if you switch the hot and ign terminals by accident it might operate the way you describe. my experience with the latter is fixing radio installs that the complaint was the radio would lose preset memory, they had the hot and ign reversed and so when key on both had power and everything would work, but turn off ign and it would lose hot, losing memory. same problem, different system.

[skymangs]

I am using a 67 Chevy truck Ignition and an EZ 12 circuit harness. There is a pink wire marked coil and a brown marked ignition. I have abandoned the coil and am using the Ignition. Also, there’s 2 ring terminals on the harness marked starter. I have them going to the B+ since there is no I terminal.

[jweb]

Make sure your ecu and fuel pump have voltage in the run position. I did an LS swap in a Cutlass and had the same problem. Fuel pump had voltage in the accy and crank position but not in the run position

Also double check all your grounds. Seems to be one problem I always have with these swaps.

[skymangs]

we figured it out, spliced the coil and Ignition wires. Starts right up now!