So I spent the past week redoing my fuel lines and installing a new fuel pump on my 2002 Suburban 2500. Pita but everything seemed to be fine until I realized the fuel gauge doesn’t work at all. The needle points straight down, I will try and attach a pic. The needle doesn’t move at all. Doesn’t seem to be a fuse for the sending unit unless I missed it somewhere.
the unit I installed in the front tank was mu1739 ac delco. Came with float arm and sending unit. Any ideas on how to troubleshoot? Wonder if the sending unit is bad, just weird it doesn’t move at all. Could the needle be stuck down there somehow?

My truck was a rear fuel tank with sender/pump in it too that I didn’t mess with at all. The gauges and everything worked great before I put in the new pump.

 

That looks to me like a wiring problem and I would say go back in and inspect all the wiring you reattached. Sometimes on an older vehicle when you try to plug a connector back in you actually have one of the wires push out of the connector. That would be the easier fix. Or you have to drop the tank and then you can remove the pump and float arm and reattach the wires and move the arm to see if the gauge moves.

 

Thanks for the reply. It's almost like the needle is pointing the exact opposite of what it should. I have maybe 5-7 gallons in the tank. I don't really want to add more to see if the needle moves in case I have to drop it again.

Thinking maybe I'll drop the tank just enough to unplug the electric connector on top and see if I can plug in my old pump just to see what happens. Maybe that could tell me if the connector is bad / if I messed it up somehow.

The pump I put in was a Delco from Rock Auto. I thought it was original factory, but maybe AC Delco isn't GM? I always thought it was. Anyways, the Delco plugged right in, same connector. But if it's reading backwards it'd seem the Ohms are off or something. I'm just throwing darts, I don't really know what I'm talking about LOL.

 

If your fuel gauge is pegging out high continuously, I think that might be a short-to-ground in the sensor/wire. Most vehicles sending units read higher ohms at low fuel levels and lower ohms resistance at high fuel levels; so short to ground would be essentially zero resistance and cause pegging high.

 

Mine is supposed to send 40 ohm at empty 250 at full. I tested the pump I took out with my meter and that’s what it reads too. Does that help?

 

No matter the quality of pump/part, you can get a bad new part sometimes.

 

I dropped the tank and checked the electrical plug to the pump and the ohms coming out of the sender unit. All checked out okay as far as I can tell. Plugging in my old pump (that still works) didn’t change anything either. So I’m thinking now maybe it’s the stepper motor in the cluster or something like that. Any suggestions how to test it without removing the cluster? Is there any way that need could just be stuck down there and needs manually pushed?

 

update: fixed it. Was the simplest, cheap easy fix ever. Once I figured out I could pop the cluster out in 5 minutes, I did that. Popped the plastic off, the needle was wedged against the cluster and couldn’t move. Popped back in and everything works great. Wish I had done that first, makes sense since everything worked before. Glad to have it drivable again. Thanks for ideas.