This problem is wierd. I am also posting this on fullsizechevy.com. So when I was driving to church today, the fuel gauge was jumping towards full. It would be fine when I was on the go pedal, but as soon as I let off to coast, the gauge would flutter, and eventually peg itself wayyy over at 3:00 position. I can't tell if it matters if I step on the brakes or not when decellerating, but it seems to expedite the progression towards F. When I step on the diesel "gas" pedal again to accelerate, the gauge corrects itself back to the normal level. I have 3/8 tank right now, and about 400 miles ago, filled it all the way up to where the pump at the station stops itself.

When I shut off the truck, I can hear this dull "d-d-d-d-d" sound coming from the fuel tank area, probably the lift pump. I have the 35 gallon tank.

Thanks everybody, any help is appreciated.

Mine did the same thing after my only warranty pump swap leaving the dealer. I just started kicking the truck in the guts (under the steering column and the powerbus) a couple times and she shut up...

Works nicely on Hondas as well.

Think its a grounding issue to the console. Any other gauges act weird? ie. turn signals making the voltmeter jump or instant temperature shifts?

Nothing like good ole' GM calibrations on the fuel gauge (mine is buried past full when full, "Full" is 2/3's tank, and 1/2 is 1/3 of a tank for my pig)...

Oh yeah, my lift pump runs for a couple seconds after I shut the engine down. I guess it's to keep the low pressure circuit primed for the next start...

That was a quick response. I know what you mean about the fuel gauge. My gasser's fuel gauge doesn't move until 70 or 80 miles has passed. On the diesel, None of the other gauges jump around, they operate normally, like the gauges on my gasser. So... I will try to pull the cluster and see where the wires to the fuel gauge go. You think that will work? Maybe an easier way??

I'm not sure if the sender on the suburban is different, but on mine there is a plastic clip that presses over a shaft and applies pressure on the 'wiper' portion of the variable resistor on the sending unit. OVer time, the clip loosens and the symptoms get worse. Mine is pegged at 3:00 all the time now. Pushing the clip back buys you some time, but a sender was $260.

The lift pump usually runs for a few seconds after shut down, as it takes a little bit for the oil pressure to fall enough for the OPS to break the circuit. Cold oil takes longer, you can hear it sometimes as long as 30 seconds after shut down.

My gauges have acted up several times in the past, jumping around as you describe.

It has proven to be an indication of 1) bad battery connection 2) bad batteries and 3) a bad alternator.

Sounds good, I will clean the connections of both batteries, and check the alternator at AZ. When AZ "checks" my alternator, will that really tell me if it is bad, or causing problems for the rest of the truck?

My friend at Kettering has a gas Tahoe, and he said it sounds like my sending unit. I will keep trying the cheaper solutions. Is there any way to tell if my sending unit is bad besides the 3:00 (completely pointing right) fuel gauge?

To refresh:
The gauge only acts up when I am off the go pedal. When I slightly apply pressure, coasting/cruising at 45MPH or so, the gauge will twitch towards F, then when I get back on the throttle, the gauge acts fine.

Good to hear my lift pump and OPS are working :)

Thanks very much :)

Well, I got 500 miles on the last tank. I put 30 gallons of regular diesel in it, and the gauge was still acting up. After about a day, and 100 miles, the gauge is FINE. No problems. I don't drive the truck that much, so it is hard to diagnose problems. I am starting to drive it more though.

Would a sending unit just not work, and then start working again? The gauge would only jump towards F when my foot was off the accelerator pedal.

Thanks guys.

OH, hahaa, I got a good squeal from the rear tires when the trans shifted from 1st to 2nd yesterday:muahaha: . Lots of black smoke too. I am getting my exhaust soon. (being shipped)