Hello, I have a 2001 2 door blazer, 4.3l. In the process of changing the fuel pump because the blazer broke down, fuel pump would not hold pressure and wouldn't come on when you turned the key, checked the relay and changed the filter. My fuel injectors were also replaced once it broke down the first time, ran for a few weeks then happened again.


Made one mistake - didn't know there was a difference between 2 and 4 door fuel pump because the first one I bought didn't fit so I researched more and found that out. Though I hooked it up and it came on but I could only find 5 volts on the wires back there. Left it hooked up while the right one came in, now neither will turn on and the 5 volts is still there.


I have a BLK/WHT, GRY, PPL, BLK wires. The PPL one is the one showing 5 volts, I guess according to the papers that's the fuel level sensor signal circuit? I thought I'm supposed to get voltage on the GRY one which should be the power circuit but nothing so I'm looking for answers and how to trouble shoot this, thanks.

 

When you initially turn the ignition to the RUN position, the grey wire should show battery voltage for ~2 seconds, and then drop to zero. The purple wire is for the fuel level sender and should show ~5 volts with the igntion in the RUN position. The two black wires are grounds for the fuel level sender and the fuel pump. They should both should show less than 5 ohms resistance to ground at all times. This link will help: https://blazerforum.com/forum/2nd-ge...eakdown-88305/

 

Ah, did not know I had 2 seconds to check voltage, thank you. I'll report back.

 

Ok, checked the wires, with my dmm leads on the gry and blk wires, key turned to run position, did not show any voltage. I checked the ohms on both ground wires, the blk and white wire had less than 1 ohm. The bigger blk wire had 5.5. I also checked for continuity from positive battery terminal to gry wire, and nothing. Not sure if it would beep or not but figured I'd try that as well. I also put the lead on the negative side of battery, other lead on gry wire and turned the key to on position, no voltage. I'm about to go check the relay again but before it was fine.

 

In the link in post #2, it explains how to activate the pump in the underhood fuse panel. While the jumper is installed, check voltage on the grey wire in the fuel pump module connector. Positive probe on your DMM to the grey wire and the negative probe to a good clean chassis ground. Post your results.

 

So went back out there yesterday and started checking from beginning to end on electrical for the fuel pump. Made a rookie mistake, forgot to bolt the ground all the way down that's on the back left of the vehicle. Once that was down, boom, voltage. Went back to work on it, got it installed, bought ac delco so hopefully I'm good for a while. Got the tank back up and started the vehicle! Ran around town with it last night, stopped at 5 different places so it had its opportunity to show me that it'll really start lol. One time it kinda had a rough start. No ses light yet but might get a scanner and see if there are any codes on it. To be honest, I've never once worked on a car (except the audio side) before this. It was fun and about to tackle other issues (heat doesn't work, oil pan gasket and timing belt cover leak, and possible transmission issue - misfires somewhere) I'll be posting up more threads and I'll post later tonight in this thread of what mistakes I made and couple things I did differently vs what I've seen in videos. Thanks for your help captain!

 

My blazer broke down aswell, my pump wouldnt work, i smashed the tank 5 times with a small hammer worked just fine since, also you need the most expensive two door only pump and there is no access panel in the car you have to cut one out of drop the tank hope that helps

 

So I just wanted to jot down some things that I ran into that might help future fuel pump replacers that happen to come across this thread.

Before working on my fuel pump, I searched and read threads - saw a great video on replacing on in a 4 door blazer. Did not know there was a difference between 2 and 4 door fuel pumps, there is. I did not know that until I was hooking up the last fuel injector - pump set in the tank no problem, no leaks or anything - just one of the fuel injectors would not fit on and after looking in the small print, saw 4 door model only on instructions. I also bought a lock ring, 2 doors do not have lock rings - they have like an O ring. I did also solder and heat shrink the new fuel connectors on and I highly recommend doing that for peace of mind.

Another thing that might help is I tried getting the filler neck off the tank, even with a