Gas Guage Fluctuates

[covetsthesun]

Hi all, Just got back from a 10 day trip. The last 2-3 days the gas guage started fluctuating from full to zero and points in between. We resorted to relying on the trip meter to let us know when to fill up. This happened years ago when Shell put some additive in their gas that messed up sensors or sending switch or something like that... but the result was the same.. gas guage fluctuation.

Not sure what happened this time. Going to the dealer tomorrow for OC and to check this out.

I'd really appreciate some advice before going to the dealer in the morning. DH wants to ignore it and just use the trip meter. I like things to work like they're supposed to.

So..what could this be and what costs could I be looking at?

Thanks all!

cts

[covetsthesun]

They did the diagnostics and said there was nothing wrong in the dash. The sensor/sending unit is the culprit, but the dealer recommended replacing the fuel pump at the same time. Right now, we're relying on the trip meter and filling up every 250 miles. PITA, but not ready to shell out $1200.00 for repairs just yet... IRS gets $$ first!

cts

[davidbt]

I have a 2004 Duramax, and mine did the same thing. Bought it used, and thankfully got a 30 day, 3000 mile warranty. The dealer had to replace the instrument cluster after replacing the tank sending unit.

[Thunderbolt]

Common problem on gm trucks since 1996. I had my intstrument cluster replaced on my 03 under warranty. Some replace the stepper motors which are available or they replace the whole instrument cluster.

ib516 wrote:
Try googling the term "stepper motor". Might be your truck's problem. It's a common issue with that vintage of GM truck.

[_40Fan]

The pumps for those pickups are expensive. List for a Delphi that I would sell is $773. About $200 for labor is what I would charge. That is if you came in the door and said I wanted my fuel pump replaced, no need to check it out.

[1oldtruck]

In my experience I have found that local shops may only save $100 or $200 on a job of that size. You may try to negotiate with the dealer for a price match or watch for online coupons. I get 10% off service flyers in the mail from our local dealers all the time.

[carringb]

Buy the fuel pump from RockAuto.com, then start getting quotes from local independent shops (or pay good neighbor in beer?).

[covetsthesun]

Well, it is the sending unit. And since they replaced all this stuff 176,000 miles ago... they suggested I replace the fuel pump too. Cost is $1200 plus tax. The adviser said it could wait as long as I was diligent about using the trip meter to make sure I didn't run out of gas.

So... that's what I'm doing for right now. I do want it fixed though. So any advice on independent's for repairs? What to look for or avoid? $1200 is a lot of money...

Thanks

cts

[rockhillmanor]

When are they going to stop putting things 'inside' the gas tank? :R
.....old enough to remember when they were under the hood. Inexpensive 10 minute job for everything. :B

[Sport45]

Be sure to complete the diagnostics before spending $$$ replacing parts. That said, it sounds like the sending unit to me too. We drove our '05 Envoy a long time trusting the odometer to let us know when it was time to fill up.

I replaced the sending unit 4 or 5 years ago and it's worked fine since. Yours has a lot more miles than ours did at the time. With 200k miles, I'd change the pump too when I had the tank out.

That said, I now have an UltraGauge in the Envoy, and I wouldn't have any problem trusting it to let me know how much gas is left in the tank. The install was a heck of a lot easier than dropping the tank.

[Sinnettc]

My '95 Silverado 1500 has the bouncing fuel gauge at times too. Mostly if I'm below 1/2 tank. We dropped the tank and replaced a bad fuel pump last year but I'm not sure if the sender is included in that unit?

[rockhillmanor]

Interesting my fuel gauge just started doing the same thing along with a high pitched whine coming from the rear. I was just praying it was a dash wire and not the fuel pump again. :{

[_40Fan]

I can just about guarantee that it is the sending unit. GM uses two small contact pads with three little fingers on them. They wear out and cause your issue.

Now, if it stayed full, or empty for a long time then jumped down or up and stayed there, then I would say the stepper motor is the cause.

[carringb]

Any shop with a decent diagnostics terminal can command a gauge sweep a selected value test to determine if it's the gauge or the signal.

[monkey44]

My 2003 GMC had the same issue -- gauges and I took it in and had all the dash gauges replaces / rebuilt. Took care of it - at first the gas gauge, then the speedometer went ... So just did them all.

If you Google this issue, you will get a lot of hits about Chevy/GM gauges in 2002-2006 truck models. As I remember it, GM even did a recall/fix for some of this ... can't remember exactly tho -- Google it and you'll find it ...