Im sure this question comes alot on the forum since blazers are known to have fuel pump issues...my gas gauge always shows full or 3/4 full and if i put it in park for 2 minutes the gauge shows that i have no fuel. If i shake the car as im sitting in it while still in park, it goes back to full tank. I replaced the filter a week ago and the pump about 9 months ago. Is it the pump again or maybe some wireing? I also replaced my gas cap. Also not sure if this is where i should post this since im new.

 

Check the ground on the pump a corroded/poor ground causes this issue more often than not!

 

So just clean the corroded stuff off if it is corroded or make sure they are attached properly...sounds easy enough...i really dont want to drop my tank again is there a way to get to it from the inside of the truck under the carpet?

 

You don't have to drop the tank to get at the pump ground. It grounds on the top of the cross member just behind the gas tank. If you have the spare tire were it mounts underneath, dropping the tire should make it easier.

From the black wire at the connector where the pump plugs in, you should see less than 5 ohms (I think) to a good, clean ground source. When I checked mine, I just scrapped all the rust off the underside of the cross member and measured from there to pump connector.

 

Thanks guys!!! Im gonna try that tomorrow and see if it works and get back to.you guys on it

 

Just keep in mind these things are known for bouncing while driving but should read correctly after sitting still.

 

Ok so i barely got time to get to it since it turned dark fairly quick but i also dont feel like following wires all day(plus im not too great with cars) ...i know the ground is somewhere on the rear crossmember on the driver side by the filler neck. Im posting a picture of a random blazer rear end in the hope i could get pointed in the right direction. would the ground be around 1, 2, 3, or am i totaly lost lol

 

Mine grounds around #1. On the top of that cross member. Where it's really hard to get to. You can just scratch down to bare metal somewhere on that cross member and measure your continuity from the pump connector to the shiny spot you just made. In theory, you could test from pump connector to any bare metal on the frame, it's all ground, but it's probably best to stay kinda close to where the ground attaches to it.

So your fuel pump runs fine, it's just the gauge that's acting up? I know on my '95, I can replace the actual pump separately from the sending unit, is your 2000 the same way? If you just replaced the pump and not the sending unit, it wouldn't have changed anything.

Also, I've never done it with a fuel level sender, but with a throttle position sensor you can hook a DMM to it, and manipulate the throttle and read the volts across it to see if it's working properly. I would think the fuel level sender would work the same way. You would have to drop the tank and pull the pump out to be able to move the float, but if you're good, you can pump the tank out, drop it, and have it back up in about an hour.

 

The image is a 4 door, if yours is a 2 door, the ground is on top of the last frame crossmember, extreme left rear corner. Tough to see, even with a mirror, gotta use the eyes in your fingers

EDIT: If the ground doesn't fix it, the level sender is probably on its way out. It can be replaced separately, but the tank has to come down and the module removed from the tank to replace it.

 

Thanks guys!!

As soon as i get time which will be on Saturday afternoon i will get to it.

I really don't feel like cutting my wire and ground it somewhere else but im sure my fat fingers will find the ground up in there. My fuel pump runs fine. My car stalled one day then bought a new fuel pump and gauge worked fine until maybe a month ago. The only way to get to the fuel pump is to drop the tank and i just filled it. I can always wait till i get low and then drop it but i just didn't like putting it back up

I do have a 4 door blazer and thanks for the tip. If the ground doesn't fix the problem i will definitely try that