Odd fuel gauge behavior

Try looking for any chafing of a wire harness near the shifter linkage. Under the dash, under the hood, under the body.

That's an excellent idea! Thank you. I will.

Looks like the sender is messed up. I have sent away for a new assembly including fuel pump, since I should do the whole Monty at the same time.

This seems to be an issue in GM products. Mother has a 99 Venture and a 91 S10 P/U that both have this problem. I had 96 Tahoe that had it (Fixed under extended warranty), and now have a 06 Trailblazer EXT that was fixed under warranty. I'm sure it's an electrical problem (short, bad ground, etc), but not worth hassling with out of warranty. We just watch the mileage, and fill the tank when we hit 150 miles or so.

John

Indeed, I have been watching miles passed and liters consumed, to estimate the fuel left in the tank. It appears that the sender, attached to the fuel pump, is made out of plastic with a variable resister coil, and the exposed conductor on that coil often wears out.

I have finally installed a new pump and fuel level sender. The problem is fixed. The contacts of the sender were missing.

How hard of a job was this? Did you drop the tank or remove the bed? Isn't the fuel pump and level sender a kit that's really pricy?

It's an easy job IF you live in an area without rust and can pull the bed.

It's still not real bad if it's rusty and you can pull the bed.

Dropping the tank is a real PIA either way.

You can get just the sender if it's the problem, depending on year you can also get just the pump. DO NOT SHOP ONLY ON PRICE FOR THE PUMP. Most of the low priced ones I have seen installed make it about a year before you get to do it again.....

Thanks for the reply. My truck is a 2000 silverado 1500 w 5.3 and about 85k miles. What is the lifespan of the pump? I can live with the fuel guage acting weird but I heard these fuel pumps are only good for 10-15 years.

IF you keep the tank full so the pump stays cool (it uses the fuel going through it to cool it) and don't run it out of fuel, change the filter ,they hold up OK. As to how long? I've seen OEM pumps go 200K and others fail at 80K.

There are a couple things that are easy to do and can give you a quick insight as to the pumps condition. One is a running amp test, you see how much current the pump takes to pump open loop and then deadhead the pump and see how it does against the pressure. Another is a simple flow test.

One of the primary reasons they fail is the connector on the pump module. The pump takes some power to run. That draw heats the connector. Get a bit of crud in there and it starts a vicious cycle, Pump on, heats the contacts and makes it take more power to run the pump, connection gets weaker and makes it worse. That is why most of the good pump kits include the harness.

You are the best, Steve. Thanks for the great lesson on fuel pump care.

Cheers!

Autumn

I did it the lazy way: I very carefully cut a hatch in the bed pan above the rear seat, operator's side, above the fuel pump. The pump and sender came as a unit, and it cost $79.08 for the part and the shipping, total.

I figured as long as I was doing the work, I would replace the pump as well as the sender. Rock Auto supplied the pump and sender in one box. The cost was $79.08

I replace the pump if it has a high running current or shows any signs of commutator failure (watch the motors current/voltage on a scope and you can see the current pulses as each segment connects), plus the harness end connector and 50% of the time need to replace the fuel lines due to rot.

Usually check the regulator operation and the spider as well.

Oh if you have a system that works fine but loses pressure on shutdown due to a crappy check valve at the module, you can get an external check valve that will retain system pressure.

Also, there are a lot of folks who ask about drawing fuel through the factory pump by using an external pump. Don't waste the time or money.