Procharged GTA

Hi all, we are switching a 1989 Chevrolet C1500 pickup(basically same setup as a 1989 TBI thirdgen) from a 350 TBI over to a Carbureted 350 with a small B&M 144 Supercharger. We have already replaced the factory TBI intank pump with a Walbro 255lph intank pump in the factory sending unit, along with a Holley Return style regulator. We have most of it installed in the truck and everything plumbed. Here is the question I have.... The truck still retains the factory ECU and complete wiring harness, nothing hooked up on the engine of course since it is now carbureted. Can we simply plug the factory fuel pump harness back into the factory sending unit at the tank, and have the fuel pump and Relay operate as it did factory, as long as we retain the factory ECU and harness?(I do understand the check engine light will likely be on, because of all of the engine electronics being unplugged), but that is ok, we will just remove the bulb. I have read several on here saying you have to power the fuel pump relay with a 12v "key on" source, but all of them I have read about usually have the factory ECU and harness removed from the vehichle. Keep in mind, that the new carbureted engine does not have the factory oil pressure switch that ties into the fuel pump circuit like the factory engine had, there is no room to mount it behind the intake where it was mounted factory, do too the design of the supercharger intake manifold. We thought maybe we could just ground that wire permanently(if we had to) and do away with the switch to make it work anyway?

Thank You, Brian

Procharged GTA

Ok, after much research, I think I have found out that the fuel pump and relay will work just as it did originally, as long as we retain both factory oil pressure switches and the ECU, and will not require any rewiring. Is that correct?

BIRD91ZRAG

iTrader: (1)

Not unless you run the factory distributor. The pulses from the pickup coil tell the ECM that the engine is turning, and that triggers the ECM to turn on the fuel pump relay. You'll need to figure out another way.

Procharged GTA

To follow up on this thread, all we did is retain both the oil pressure sender and the oil pressure switch behind the intake, along with the factory ECU and fuel pump relay, and the fuel pump operates just as it did factory. We are running a Holley 750 carb and aftermarket Top Street Performance billet distributor(MSD 8360 copy), seems to do just fine so far, fuel pump prime even works just as it did factory when the key is turned on.