I need some wiring advice.

[Dale Merritt]

I recently dropped in a fresh engine into 90 GMC. It's a .030 350, with flat tops pistons,268H comp cam,vortec heads, edelbrock performer rpm air gap intake and a 650 Holley spread bore carb. I installed a new hei distributer and have the wiring figured out. What I need to know is, does the fuel pump circuit have to be rewired ? If so ,how? Thanks in advance.

 

[Schurkey]

Holley-and-HEI sounds like the computer is entirely disabled. With no computer, there's going to be nothing to turn the fuel pump relay on.

1. You need to figure out how the fuel pump is going to be turned on and off.

2. You need to reduce the fuel pressure from whatever the pump is capable of--13+ psi--to more like 6 or 7 psi.

"I" would scrap the "Holley and HEI", go back to a proper TBI system with full computer control. But that's me.

 

[884x4310ci]

Does your block have the hole for the fuel pump or is it a newer block ? I used a mechanical fuel pump and did away with the intank one. You just need to reroute the fuel line.

 

[RichLo]

Mount a mechanical regulator on the firewall with a return line back to the tank. Then wire the fuel pump relay to the ignition switch so it turns on and off with the key.

TBI fuel pumps can be regulated down to carb levels but vortec pumps cannot.

 

[ZRoe]

Mount a mechanical regulator on the firewall with a return line back to the tank. Then wire the fuel pump relay to the ignition switch so it turns on and off with the key.

TBI fuel pumps can be regulated down to carb levels but vortec pumps cannot.

Be careful with wiring it to the ignition. You only want the fuel pump running when the engine is running. A good way to ensure that is the case is to wire in an oil pressure switch to the fuel pump relay. That way if the engine dies the pump stops. This is especially important in the event of a crash, no need to add fuel to an already bad circumstance.

Sent from my moto e5 supra using Tapatalk

 

[PlayingWithTBI]

"I" would scrap the "Holley and HEI", go back to a proper TBI system with full computer control. But that's me.

Ditto!

 

[1989GMCSIERRA]

You’ll need to wire your fuel pump as a key on accessory. Basically turn on the key gives power to the pump. The key is the on switch.


You can always wire it up with a independent toggle switch. Problem is if you forget to turn it off. But you can wire it so the switch gets power from a key on source only.

You’ll need a relay to turn on the pump.

 

[Schurkey]

Needs to be "hot" in "Run" and "Crank", but not in "Accessory" and "Off". And of course, routed through an oil pressure switch in "Run" but not in "Crank".

 

[89GMCJOHN]

Does your block have the hole for the fuel pump or is it a newer block ? I used a mechanical fuel pump and did away with the intank one. You just need to reroute the fuel line.

X2