Approx 300 miles ago I replaced my fuel pump with a Walbro 255. The stock sender assembly including wiring all looked in mint condition so that all went back in. Fast forward 300 miles, no prime. I had power all the way to the socket by the tank, and banging on the tank didn't help.

I did what I said I would never do again and dropped the tank. I pulled everything out and the pump runs fine. However, there is corrosion on the positive pin of the stock sender unit harness where it passes through the metal gas tank ring. Sure enough, infinite resistance on this pin only until cleaned. I've seen photos of burned up connections like this on GM vehicles due to a loose connection and I've also seen corrosion when the two metals on each side of the connector are different (e.g. copper and aluminium).

I'm going to replace the sender unit and harness. This does not seem like a place where dialectric grease needs to be used! Anyone else seen this?

 

I've seen that on other applications. Start with a little corrosion creating resistance, and a new pump using higher current, and the situation becomes a cascade of heat, resistance, and erosion racing to the finish line to see which one will kill it first. That's always one of the risks of a "high output" pump on 40 year old stock wiring components.

 

I would highly recommend replacing the in-tank wiring with the kit from Racetronix. All new components and has dual power and ground wires to power your upgraded pump. I had a Walbro 255 fail after 150miles due to high resistance in the in-tank wiring. I was able to test the voltage drop of the wiring after dropping the tank for the second time when the pump stopped working. The old factory wiring was dropping voltage on both the + & - which is what killed the pump. Connected to a battery and a good used Walbro pump I had 12v at the tank connector and 7v at the pump.

 

Do you have a link to the correct Racetronix kit? I was looking for options there yesterday but drew a blank. I already have their wiring harness kit (FL98 Fuel Pump Wiring Harness, FPWH-005) plus improved chassis ground, but it did not include anything starting at the wires that enter the fuel tank. This looks to be the current equivalent of what I currently have: https://www.racetronix.biz/p/fl98-19...ss-hd/fpwh-035

 

Looks like you mean this one: https://www.racetronix.biz/k/fl98-f7...ly/bcwa-fl98hd

This would give redundancy on the positive but not on the negative. Better than nothing and reduces the series resistance, but won't do anything if the negative decides to corrode (might not happen, due to polarisation).