1978 Caprice - 5.3 LM7/4L60E - Stock, daily driver, 1994 Caprice gas tank and sender assembly, Walbro 255 lph pump.

After 5 years with no issues, my fuel pump started acting up. Then died. I replaced it (New Part# GSS343G3 (Walbro was bought by TI)). The new pump, after 200 miles, quit. The car was on jackstands and the pump would not work (no start, no 5 second prime when key on). I have tested the wiring in the car and it is working perfectly. I pulled the pump and tested the pump while submerged in a bucket of water and it all worked. I applied 12v at the weatherpack connector on the sender, worked. I disconnected the bulkhead connector on the sender assembly and applied 12v there. Worked perfectly. I'm assuming I have a bad connection somewhere, but I cannot find it. One issue that I noticed is that I tested the continuity on the weatherpack connector and all of the prongs had continuity with each other, even the sender wire. It's worked this way for 5 years with no issues, but I didn't expect to find this. I wired this per Racetronix's instructions (When I built the car I upgraded the pump to bulkhead harness and added an redundant ground that goes through a bolt I drilled and mounted through the bulkhead and leads to the car). I'm not sure where to go from here. Everything I bench tested (continuity, 12v positive) and everything worked as it should. I'm not sure what to do next. There must be a bad connection somewhere, but I can't find it.

Here's the weatherpack connector on the topside of the sender assembly. Applying 12v makes the pump work. Also, all 4 prongs (two grounds, power and sender wire) have continuity. I thought the sender wire, at least, would not have continuity to the power wire, but I supposed the way Racretronix had me run extra grounds, it makes sense.


Here is the bulkhead connector. Removing this and applying 12v to the red wire caused the pump to work fine. The screw into the top of the bulkhead is a redundant ground that leads to the car itself.


I tried to get as many angles as I could to show the wiring setup. I tried manipulating the wires to see if I could reproduce a problem but was not able to get it to stop working.

 

I am not familiar with Racetronix equipment but if it does not prime and the wiring is good, I would think that the Racetronix module has failed. Have you spoken with the tech support people there?

Rick

 

I haven't spoken with Racetronix. They basically just sell Walbro (TI) pumps, and when last dealt with them when I built the car I was so put off with their customer service I don't want to ever deal with them again. I recently replaced the pump with a new walbro. I can't understand why it wouldn't kick on while in the car, but then took it out and it bench tests fine. All the wiring in the car is good, tested with a test light.

 

The connector that plugs into the bulkhead most likely spread out and is having intermittent connection issues. Take a look at that plug that goes into the bulkhead

 

IIRC, when I bought my Walbro pump from Racetronix, I also got an upgraded pump wire harness for the original caprice unit. Did you get that too?

 

I did take apart the connector to the bulkhead as mentioned. After checking everything else, it seems like this is the only place that could be the problem. I noticed a couple things. One of the pins seems to be shorter than the others. Also, it's hard to see, but the connector for the power wire seemed to be a bit darker than the others, possibly corrosion. When I took the pin out, it broke.

My question is, what type of plug/pin is this called? I need to get a new one, but don't know what to call it. I also want to replace the connector through the bulkhead.

 

Just buy a new in tank wiring harness. They're like $10ish

 

I suppose that is a good point, I hadn't really thought of that since my goal is to try to stay away from racetronix, but I need to get my car back on the road. On their website I was able to find the new harness. They also have the connectors.

I double checked and the pin that appears to be broken off/shorter, or maybe even burned off, is the same pin that is for the big red power wire for the pump. Could a power surge or a bad connection have caused this to actually burn the pin?

 

Yea I hear ya on staying away from Racetronix. I gave them too much for too long just for their stuff to fail or flat out not work