SC fuel pump wiring

dwightp · 03-09-2003, 01:36 PM

Ran into an interesting problem and need some feedback from those "in the know".

I'm trying to modify the fuel pump relay wiring to work with an aftermarket ECU. This ECU provides a gnd when it wants fuel pump running. However, the existing SC wiring appears to supply power to fuel pump relay with ignition on and relay appears to be normally closed. Providing gnd to energize relay opens it and interrupts current flow to fuel pump.

I'll need to modify wiring to relay such that + 12v is present at all times, relay is normally open, gnd from ECU will provide gnd to relay to close it.

Please clarify or correct me if my assumptions are wrong here.
Please verify or clarify what I missed.

Thanx

dean · 03-09-2003, 05:19 PM

I think you are right. The thing I am sure about is that the reason they do it that way is for the safety fuel pump shutoff when the motor is not running. There is a switch in the air flow meter that shuts or opens and the fuel pump runs only when air flow is present, or cranking. The rev limiter also opens the relay to prevent overrevs. Do you have a wiring diagram? Thay would clear things up
Good luck

dwightp · 03-09-2003, 05:28 PM

I do have some wiring diagrams but they don't go into much detail of the internals of the flow meter or rev limiter. I don't have the flow meter any longer.

I may have to go with my guess after I try further ringing out the wiring in this area.

Thanx

dean · 03-09-2003, 05:38 PM

You don't have to concern yourself with the internals. As long as you know if the relay is open with ground or power. It has been 2 year since I messed around with the wiring on my car and I forget which way it goes. I do remember that it seemed ass-backwards when I figured it out. But it works good