2002 Suburban 6.0L fuel system

I've tried to find a thread about my problem, hoping I'm not the first. But my 2002 Suburban with a 6.0Litre gas engine, is having trouble with the fuel gauge system. This truck, I guess because of the bigger engine, has TWO (2) fuel tanks. Everything seems fine as far as running goes. It doesn't stall, only had it refuse to start once, but only after trying three turn overs! But, my fuel gauge intermittently will stop working and the LOW FUEL message comes on. It seems to happen if I'm close to a quarter tank and I leave the truck off for the night. After I fill the tank, in a few minutes, the gauges are back to normal and showing full. My mechanic and I feel it has to do with the upper, smaller tank and it's "Transfer Pump" and sending unit. But are there relays that could be the problem? I believe last week I heard the upper pump running when I was at a quarter tank and it was load because the upper tank was empty!

I've tried to find a thread about my problem, hoping I'm not the first. But my 2002 Suburban with a 6.0Litre gas engine, is having trouble with the fuel gauge system. This truck, I guess because of the bigger engine, has TWO (2) fuel tanks. Everything seems fine as far as running goes. It doesn't stall, only had it refuse to start once, but only after trying three turn overs! But, my fuel gauge intermittently will stop working and the LOW FUEL message comes on. It seems to happen if I'm close to a quarter tank and I leave the truck off for the night. After I fill the tank, in a few minutes, the gauges are back to normal and showing full. My mechanic and I feel it has to do with the upper, smaller tank and it's "Transfer Pump" and sending unit. But are there relays that could be the problem? I believe last week I heard the upper pump running when I was at a quarter tank and it was load because the upper tank was empty!
You stated gauges.Does it have 2 fuel gauges?
Or a factory dual tank set up?
Your Quote.
After I fill the tank, in a few minutes, the gauges are back to normal and showing full.
end Quote.

On a factory dual tank SETUP WITH ONE GAUGE the primary tank fuel sending unit controls the lower half of fuel gauge.
If gauge says low fuel or empty with over 1/4 tank of fuel the sending unit on that tank is bad.

The truck has ONE fuel gauge plus the message centre. My mechanic did put it on the machine and got codes for TWO sending units and some how they are linked to the ONE factory gauge! Everything is factory equipment! The codes did not specify which sending unit or pump was the problem!

The tanks are not set up as the usual duel tank system! They are linked automatically! You can not choose which tank! I believe the smaller upper tank was added because of the size of the engine.

The truck has ONE fuel gauge plus the message centre. My mechanic did put it on the machine and got codes for TWO sending units and some how they are linked to the ONE factory gauge! Everything is factory equipment! The codes did not specify which sending unit or pump was the problem!

The tanks are not set up as the usual duel tank system! They are linked automatically! You can not choose which tank! I believe the smaller upper tank was added because of the size of the engine.

Primary tank fuel sending unit is your problem child.:banghead:

Is there any way to make sure it's the primary sending unit? The codes he got didn't help.

Is there any way to make sure it's the primary sending unit? The codes he got didn't help.
I done told you it was the problem.
So to test it just.
Substitute a know good one or just replace it an be done with it.
And do not even try jumping or grounding tank unit.

Is there any way to make sure it's the primary sending unit? The codes he got didn't help.

yes your mechanic can use a resistor to replace the sender at the fuel tank connections . if the fuel indicator works correctly as he changes the resistance then the in tank sender is bad. then you can remove the sender and use meter to see with the float movement that the resistance changes using the meter.

if he is a mechanic then he should be telling you this or just do it.

my guess is he is an idiot mechanic.

I also would just replace the complete fuel pump/sender assy ..ac delco and its done..

Thank you for all the input! I think I'm just going to drive it using my trip odometer to keep track of my fuel level, till one of the pumps actually dies!

Thank you for all the input! I think I'm just going to drive it using my trip odometer to keep track of my fuel level, till one of the pumps actually dies!

the sender unit used on these are defective GM parts. I myself with a 2000 have the sender issue that will not work after sitting but when the tank sloshes around works. When you do the complete pump assy, you purchase an ac delco or the delphi. you or you instruct your repair guy to solder in the new connector [its different] and seal with heat shrink. he will probably half azz the job and just use crimps ..it will last a couple of years with that ! GM dumped the OEM design this will be the new part that works .