Hi!

I have a 1998 blazer S-10 4 door 4wd 4.3l. The fuel pump died on it so I replaced it with a AC Delco fuel pump Assy. with fuel sender Assy. I had also replaced the wiring harness plug they give with you. The fuel gauge first read full when ignition turned on but after about 20 seconds went to empty and now always reads empty and low fuel light is on. I have about 1/3 tank of fuel. I removed that AC Delco Fuel pump and installed another one and the fuel gauge still reads empty. While troubleshooting I connected the ist AC Delco fuel pump Assy. outside of the tank to the 4 pin wiring harness back at the tank tank and the fuel gauge reads normally when the key is turned on so it appears the fuel sender works while out of the tank but doesn't when installed in the tank. Puzzling to me for sure but I'm thinking about something like grounding etc. Does anybody have any ideas? Thanks!!Rick

 

I got the same exact problem, but i was thinking i messed up the wiring because there was one wire i kinda got confused on.. but you said you took your pump out of the tank and and it worked fine? so do you mean you moved the float up and down and it moves the gauge??

The only ground is on the rear cross member right next to the filler neck, but if it wasnt working the pump its self would work either. I think maybe next week ill tare into it again so ill keep u posted on what i find.

 

Thats right, the pump whose fuel level doesn't work in the tank works outside of the tank as I can move the float lever and it moves the gauge. I agree about the ground as I wouldn't expect the fuel pump to work. I appreciate the post if you find anything. So far I've put too many hours into this without any success so thats why I thought I would reach out to the forum for some ideas. Thanks!

 

Did either of you ever fix the problem?

 

I came to the conclusion that i had a bad sending unit, i took the pump back out and hand operated the float and it still only went to 1/4 tank

 

The ground for the sending unit is actually up by the engine block. The ground for the pump itself is on the crossmember by the filler neck. If you're fuel guage doesn't go all the way to empty, and when full reads higher than full it's because there's too much resistance on the ground wire for the sending unit. Check this thread for diagnosis details: 98+ Fuel Gauge Diagnosis.

 

Hmm.. Too bad thats only for 98+ but my gauge only goes up to 1/4 tank when i have a full tank. But the gauge still drops like normal as i use gas, so when the gauge reads empty i have 3/4 of a tank left.

 

I still used it to fix the gauge for my '96 after I replaced my fuel pump and updated the harness to the new flat 4 pin plug. I'm pretty sure that the resistance values are the same even for all 2nd gen trucks.