I have a 2003 2500HD with the Duramax diesel. I've had the instrument cluster repaired twice now and I'm pretty sure my gauges are good. My fuel gauge works fine until I get down to under 1/4 tank. Below that, when I put on the brakes the gauge drops to empty, the light comes on, and it stays that was until I stop or accelerate again. Then it jumps back up, sometimes to 1/2 tank or so. It becomes more erratic as the fuel level drops.

I think the problem is the sending unit. I have been living with it and just fill up when it starts to happen but it makes me nervous because I don't know how much fuel I have. Is there anything else that it could be?

I have been investigating this and I thought the sender and pump were the same unit, but apparently that is not the case on the diesels. I have found a replacement EXTERNAL fuel pump and a separate sender unit for sale. Is there actually a pump in the tank?

Here's the pump I found, which it says is OEM P/N 23484681 or EP1020:



This is the sending unit, Delphi P/N FG0166


Summit Racing says it doesn't include the pump, so what are the lines and fittings for?

http://www.summitracing.com/parts/df...make/chevrolet

Is there yet another pump in this module? I know there is an injection pump on the engine but I don't see why there would have to be two pumps before it.

I know it's a royal PITA to change these things, and you can either remove the bed or drop the tank. I would like to fix it but it's not something I'm looking forward to doing.