Crazy Duramax fuel gauge

[olds48]

I have a 2001 Duramax.Bought it used with 156,00 miles on it.Everything works fine but the fuel gauge is wierd.It seems to work fine and when the fuel gets low it brings on the low fuel light.BUT,when you fill the tank all the way,the first 30 miles or so,whenever you stop or back up it brings on the low fuel light???The gauge will drop instantly to "E" and then BOING just shoot straight back to "F" and the light will ,of course, go out.Don't really hurt nothing,just wondered if anyone else has run across this.Really annoying cause that darn idiot light is super bright at night.

[jmarksdragster]

Most likely the tank sending unit, not cheap. I have a 99 Suburban Diesel I need to replace a second time, I think I was victim to a Chinese GM look-a-like part (bought on internet). I will go to the dealer next time. I would ignore it till it gets unusable.

[olds48]

Kinda what I was thinking.The way it jumps around at only a full tank makes me wonder if it is shorting out possibly????Just don't want it to fall off and possibly stop me on the side of the road.You say expensive??How much...or do I want to know?

[jmarksdragster]

The sending unit is a variable resistor. As it goes up and down the resistance changes. If you hit a bad spot with no connection it will make the gauge jump. Funny you mention fall off... that is what mine did. I hear it rattling in the tank when the fuel level is low. I keep track by watching my mileage and filling up at 500 miles. Be ready to spend $200 to $500. I would leave it alone till it gets worse. I may be crawling under mine next week....

[olds48]

The sending unit is a variable resistor. As it goes up and down the resistance changes. If you hit a bad spot with no connection it will make the gauge jump. Funny you mention fall off... that is what mine did. I hear it rattling in the tank when the fuel level is low. I keep track by watching my mileage and filling up at 500 miles. Be ready to spend $200 to $500. I would leave it alone till it gets worse. I may be crawling under mine next week....

500 miles!!!???Man,I can't get more than 375 or so out of mine.And that's sucking fumes.Thanks for the info though.

[jmarksdragster]

500 miles is about 30 gallons, I have a 40 gallon tank.

[olds48]

Most I've ever put in mine is 28 gallons :shock:

[cpgeneration]

check the connections for a good ground, might save you a lot of work and money.. :D

[johnracer]

GM has had a lot of trouble with the sending units on it's trucks. I'm sure that's it. I've replaced a ton of em....