Since my 92 and 93 trucks were modified/updated to the LSx powertrain and the fuel pumps were also updated to Walbro 255 LPH pumps, I decided it was time to update the power supply for the pump. If you've ever worked on one of these things you'll know that the stock wiring going to the pump is about 18 gauge wire(the new wire is 10 gauge fine strand copper). If you put a heavy load on a small wire it acts like a resistor and drops the voltage via resistance and heat. Lower voltage means that the pump is going to turn slower. A slower turning pump means less fuel supply and less pressure. Now comes the cure, the RACETRONIX HOTWIRE kit. RACETRONIX does not stock a plug and play kit for the trucks but will build you one if you call them. I found a kit on their website that I purchased and modified for my specific purpose. Buick Fuel Pump Offer - GNTTYPE.ORG I ordered the one on the right Grand National PnP Fuel Pump Upgrade Harness but the one on the left should work also. Notice the notches cut on the connector that "sex" the connections. The one on right would not plug into my harness so I got busy cutting wires. The harness comes with a nice waterproof military type relay.I cut the wires coming from the front of the truck about 3" before the connector. Only cut the black and grey wires, the purple wire is for the fuel sending unit. Cut the grey and black wires on the RACETRONIX connectors and toss the RACETRONIX connectors. Next just strip back the insulation and solder and shrink wrap the relay into your factory harness connecting grey to grey and black to black. Connect the large red wire coming from the relay to the grey wire/fuel pump feed. The grey wire coming from the front of the truck will be triggering the relay to feed power to the pump and the black wire is the ground to the pump and the front of the truck. You will also be adding a new ground near the fuel tank and the harness supplies a clip that adds additional fuel tank grounding for static electricity suppression. To mount the relay I simply removed the stock ground bolt on the frame and put the new ground, the existing ground and the relay on the bolt. Next you will need to run the main power wire from the relay up to the large 12V power lug on the alternator. The connector that came with my harness was only 1/4" diameter so I had to buy a 5/16" connector and crimp/shrink-wrap it onto the fused connector end. Since I have an Fbody accessory setup I chose to cut and shorten the main power lead rather than to bundle it up under the frame. The fuse at the alternator end is setup to be mounted anywhere so I drilled a small hole through the plastic on my alternator and stuck a carriage bolt and nut through the plastic and bolted the fuse mount there. All that was left to do was take the supplied zip ties and bundle all the wires up out of the way from hot items and pinch points.
I'll try to get some pics up when I get my truck back.
Also supplied with the kit is a supplemental ground to increase/improve the ground flow from the battery to the body.
BTW, the above link is for the correct pump for the OBS pump to GenIII conversion.
Reply With Quote
