Run & Start for a Sniper or FiTech

[65 Dartman]

A friend emailed me about using a FiTech or Sniper on his 80’s Dodge truck. He sent me a picture of the schematic of his ignition switch from his truck to see what I thought. I told him these FI units require power to the TBI during both the start and run from the ignition switch. He is thinking that the J2 14DB Circuit in the upper circle supplies power in both run and start. It definitely does in run I believe. If that’s not the case, he believes power is supplied during start in the bottom circle in the P5 20GY/RD• circuit which he said goes to the brake warning switch and parking brake switch. I’n not an electrical guru but in thinking about it and looking at the switch schematic, I think his logic is reasonable and should work. any electric experts care to comment?

 

[Professor Fate]

I can't tell from the pic, but what year exactly is the truck?
Depending on the year, the 80s could have used at least 3 distinctly different wiring schemes for gas V8s- the familiar Chrysler electronic, a more or less "Lean Burn" type system and controller, and the '88 and up TBI systems and computers- all of which had slightly different wiring. For what it's worth, the standard Chrysler ignitions needed the IGN1 and IGN2 (at least that's how they were labeled on pass cars) twisted together for the power feed, and I believe the TBI systems had a dedicated start/run lead in the system. I'm not sure about the Lean Burn type system, it's been ages since I've dealt with one...

 

[67Dart273]

DO NOT use the start wire. This is because if you tie the "start" wire and the "run" circuit together, the run voltage will backfeed and engage the starter, anytime the start relay is grounded through the neutral safety switch

First actually CHECK that the "run" line goes dead

I cannot see enough of or read that diagram. The switch in the older cars all had "IGN1" and "IGN2" which you tied together for this type purpose--for EFI or for an ignition that does not use a ballast

I "believe" that the later trucks eliminated this. Does the truck still use the "old looking" style starter relay? If so have him look for a FIFTH terminal on the relay. Use that to supply cranking power to the EFI

If the truck has a starter relay like this........

use the "bal" terminal to supply cranking voltage to the EFI

If not, the bypass circuit MUST exist somewhere. Does the truck have a power distribution/ fuse/ relay box? It may be that the plug in starter relay "if used" holds the key.

WITHOUT A DIAGRAM I am without a better answer

 

[65 Dartman]

I will contact him and see if I can get some more info