Wiring harness confusion - Third Generation F-Body Message Boards

mavcar38 · 09-16-2009, 10:30 AM

I have an 89 5.7 TPI im converting to carb. I have a brand new crate 350hp I just dropped in. I had the 700r4 rebuilt with a non-lockup converter so Im not concerned with the tcc switch. I keep reading different opinions when it comes to the wiring harness. Ive heard some say to take it out and others say to leave it in and cut out later. If I'm disconnecting the harness from the computer anyways then what good is it to leave the harness in? Im going to use the oem fuel pump with a fpr. Is it best to wire the fuel pump to the ignition or the alternator? Not an expert at this so any help would be greatly appreciated. Thanks much.

five7kid · 09-16-2009, 11:06 AM

Go ahead and remove the ECM harness. Cutting doesn't make a lick of sense to me. There is always someone out there who needs an unmolested harness.

Wire the pump relay to battery power. Use ignition switched power to energize the relay.

mavcar38 · 09-16-2009, 07:53 PM

Can you tell me what to do with the two heather hoses that come out the firewall and into the plastice piece? I got the harness disconnected from the computer and through the wheel well. Im just concerned about taking out a wire I need and keeping everything else functional. Any advice?

1ADan · 09-25-2009, 08:32 AM

If you don't have an ECU (computer), the entire passenger side harness can come out. There should be no wires that you need to worry about reusing.

As for the heater hoses, those are for your heater core, don't get rid of those. Unless you don't want heat in your car. Then you can think about it.

mavcar38 · 09-27-2009, 04:08 PM

Which one is the pump relay. There are 3 or 4 relays on the drivers side? Then I wire the pump relay to the ignition?