Thread: Help ! ? with New(er) GMC Truck...

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OK Guys...I need your help...

For the past few months, my fuel guage on my 99 GMC 1/2 ton truck has been going weird on me...I can fuel up, have a full tank of gas, and the guage will still read empty, and then it will jump to full, and then to 3/4, and back to full, etc.

Sooooo.....

I took my truck to the GMC dealer today, to have it looked at.

After not hearing from them all day (grrrrr...) I finally called them at about 5:30, only to find out that they had just got the truck in...(double grrrrr......)

They determined the problem to be a fuel sending unit (I guess I'm spelling this right...).

They told me it would be about $500 to fix it. ($170-something for the part, and 3 hours labor)

I told them I couldn't afford that, and I would come pick up the truck....
And of course, the shuttle driver had already left for the day, so, I am having to wait for a another ride, so I can pick up my truck...(triple grrrrrr......)

Anyway, sorry about the venting...I'm just extremely frustrated right now...

My question (finally) is this: What exactly does a fuel sending unit do, and if I don't replace it, am I gonna be in trouble?
(i.e., if it isn't fixed, will I not be able to drive my truck, or does it just control the reading on the guage?)

Please help me...

Thank you....
-Misty

it just controls the guage. if you know the fuel mileage you get you can figure how many miles per tankful you get. just keep an eye on your odometer. i've been doing this for years and didn't run out yet

The fuel sending unit is basicly a voltage regulator and your gas gauge is none the less, a volt meter( but reads small amounts of voltage ), on older vehicles, tanks had floats in them, the float was on an arm, attached to the sending unit, the float goes down, the sending unit decreases the voltage to the gauge, if the sending unit is decreasing the voltage wrong ( or increasing it instead ) it will do things like that. If you can figure out how much gas you have by seeing patterns in the gauge readings, that's fine, it's not gonna matter if that gauge works or not but, until you can get it fixed or see the patterns, leave a full 5 gallon gas can in the back so you can get to a station if you run out.

Any chance that its only the slip-on wire connector that's corroded or a rubbed wire short?

Especially since it reads full, then empty, then 3/4.

Bert

Originally posted by Hot Rod Angel
OK Guys...I need your help...

For the past few months, my fuel guage on my 99 GMC 1/2 ton truck has been going weird on me...I can fuel up, have a full tank of gas, and the guage will still read empty, and then it will jump to full, and then to 3/4, and back to full, etc.

Sooooo.....

I took my truck to the GMC dealer today, to have it looked at.

After not hearing from them all day (grrrrr...) I finally called them at about 5:30, only to find out that they had just got the truck in...(double grrrrr......)

They determined the problem to be a fuel sending unit (I guess I'm spelling this right...).

They told me it would be about $500 to fix it. ($170-something for the part, and 3 hours labor)

I told them I couldn't afford that, and I would come pick up the truck....
And of course, the shuttle driver had already left for the day, so, I am having to wait for a another ride, so I can pick up my truck...(triple grrrrrr......)

Anyway, sorry about the venting...I'm just extremely frustrated right now...

My question (finally) is this: What exactly does a fuel sending unit do, and if I don't replace it, am I gonna be in trouble?
(i.e., if it isn't fixed, will I not be able to drive my truck, or does it just control the reading on the guage?)

Please help me...

Thank you....
-Misty

100.00 hr. labor? that would cost you about 250.00 here. got to be a good independent shop up there that will do it for less than that. if you keep fuel in the tank you dont have to have it though.

I think SBC has a point, it sounds like wiring connections more than the tank sender. Buy a can of electrical contact cleaner from Radio Shack and clean up all the connecters.

Thanks for your help guys !

I'll check into the wiring connections first, and then, if that's not it, I'll just do like I've been doing...just keeping an eye on my odometer, and filling up when I know it's getting low!

Thank you ! You guys are the best-est!

*KISS*KISS*

I have been riding in my 65 C-10 for the past couple years without a working fuel gauge. Been telling myself that I'm going to fix it when i change tanks. I just fill up every evening right by my house. That way in the morning i know i have a full tank and no worries if im running late 4 work. I also keep a 5 gal can in the back for "just in case". Had to use it once... If you do keep a can though ... I recomend emptying it into the tank every other time or so that you fill up. That way the gas doesnt get old on ya.

HRA, make sure you check any and all grounds also. Sounds as though you are experiencing an intermittent open circuit. If it was a short circuit it would read full all of the time.