Puzzle. 1996 Silverado Burning up Fuel Pump Relays

[JimmyMack]

Hey All,
So my 1996 Silverado 1500 stopped on the street. 5.7 Vortec, 240k miles. Fuel pump relay was too hot to touch at first. I hurried and put a new one in. Started and ran great for couple weeks. Then, same thing. New relay and I did some fuel pressure and voltage tests from a couple youtube videos. Fuel pressure around 60-62 at startup (no dropoff). Testing the relay center box showed pin 86 (12.62 volts), pin 87 (12.32) pin 30 (12.38) and there was no voltage at pin 85. (I'm not even sure what these tests are supposed to tell me, but it was cool to do them). Visually, the spot where pin 30 plugs in was burned, the plastic melted a bit and the wire pulled up higher than the others. I've been told it could be many things, from fuel pump (the truck still starts and runs strong with fresh relay) to crankshaft sensor (?) and all kinds of wiring issues (replace the whole relay center). It's a great old truck. Just need a little advice on how to proceed. Appreciate y'all.

[Blue Bowtie]

If the problem is researched, it becomes apparent that the reason for GM changing the fuel pump connector and harness at the tank was valid. The fuel pump can draw more current than the original connector design could support in the long term. There are literally thousands of accounts and photos of the fuel pump connectors at the tank unit melting and burning due to overcurrent.



That same current must also pass through the fuel pump relay and through the power bussing in the UEC. A relay that is optimistically rated for 20A (really a 10A design) should never have been used there. Having experienced a similar problem, I added a second (heavier) relay in parallel.

[JimmyMack]

Blue Bowtie,
Thanks for the reply. That makes ense. Just how did you add the other relay? Difficult to do?

[Blue Bowtie]

I tapped into the wiring in the UEC, routed out spare wires for the pump relay signal and pump power circuit, tapped directly into the auxiliary battery power (upfitter connection) and fed power to the relay. It required disassembly of the UEC, tapping and soldering the extension wires, are re-looming all the wiring into the convoluted protection tubing.

That's been about 3 years and it hasn't had a hiccup since.

I had to do the same thing on a '97 Sierra some years ago - After other shops had replaced the fuel pump three times. it never hiccuped after the relay addition and wiring upgrade.

[JimmyMack]

Blue Bowtie,
Whew. I had to ask, didn't I? Lol. Thank you for the info. I would love to do the mod but I am lost unless I can actually see how to do something. I can follow your steps but am not sure what wires are what, which goes where, stuff like that. Glad you found a solution for what seems a common problem. Thanks again.