The Lt1 is from a 94 vette, it is in an 89 v6 firebird. I installed the Racetronix in-tank fuel pump and harness, which takes power directly from the alternator, however the painless wiring harness has a grey wire which is supposed to connect to the fuel pump. Do I still need the wire from the painless kit?

 

I'm not quite understanding what you mean by"takes power from the alternator". Your fuel pump will need to be switched on by the PCM. The output from the PCM "turn on pump" signal will drive a relay which in turn powers the fuel pump.

 

The Fuel pump doesn't need to be turned on by the PCM, it just needs to be turned on, either by the PCM or by an ignition source.
The best way to run power to the pump is from the battery to the relay and from the relay to the pump, and either have the PCM or ignition activate the relay.

 

I just ordered that harness. Let me know how you get this worked out. I have a similar issue becase I have an LS1 engine.

 

It doesn't need to be ran from the PCM, but who want's there fuel pump to run 100% of the time whenever the ignition is clicked forward one notch? Not me.

 

If you use the painless harness it comes with a fuel pump relay in the harness.

if using an intank pump im quite sure this relay will suffice.

if using an Aeromotive external pump then you may want to use that relay to control another High amp relay. then wire the high amp relay from the batt to the pump to ground with sufficient size wire.

If using an external inline pump i suggest using the aeromotive fuel pump controller. this varies fuel pump voltage based on engine rpm, to help keep the pump cool on longer driving conditions.

 

the painless harness plugs into your stock fuel relay, but the racetronix harness comes with its own relay, so now I have 2 and am not sure which to use...

if I connect the grey wire from the painless harness to the racetronix harness then I will probably disconnect the painless relay and just use the racetronix relay. I will see if it works when I hopefully start the car in about a week...

 

You have a similar setup to mine. I also used a '94 Vette Lt1. How about some pics when you get a chance. I used the Painless harness and a new/stock relay. It's been working fantastic so far for me.