fuel gauge

sisbug · #1 03-25-2011, 10:30 AM

We had some heavy rains and I noticed my gas gauge went from where it was to above full. Later that day it came back to normal then dropped below empty. Now for the most part it is stuck on Empty. Somedays it will come up to around a quarter and then slowly drop back to below Empty. Now my check engine light is on and saying po460. Does anyone have suggestions on how to test this. I think maybe it is a short somewhere. If it is the sending unit can I replace that without doing the whole pump and all? Should I drop the tank to check or is it easier to take the truck bed off? Any feedback would be appreciated as most of this is new to me, teaching myself as i go along.

FireRanger · #2 03-25-2011, 11:09 AM

Well P0460 is "Fuel level sensor trouble". So the light is telling you what you already know.

Pegged full is a direct short to ground. Pegged empty is broke open circuit. What you describe sounds like the wiring to the sender is fucked. Unless you have messed with things nearby, it is probably at the top of the tank.

Dropping the tank vs lifting the bed is 6 of one and a half dozen of the other. They're both a major pain in the ass.

sisbug · #3 03-25-2011, 02:47 PM

Thanks for your feedback. I was thinking it may just be a wire issue and not the sending unit. We live in a very rocky part of the desert and get mice and rats. I am thinking maybe one of them may have chewed something on top of the tank. Is it possible to check these things on top of the tank without dropping it?

sisbug · #4 03-30-2011, 01:25 PM

Pulled the tank this weekend and had the sending unit tested. My unit is bad. I found the replacement one online, the local auto places only sold the whole unit. So hopefully I can get the old one off and the new one on the existing one ok.

sisbug · #5 04-08-2011, 04:01 PM

So looking for some feedback again. Changed the sending unit and put it all back together and no change. check engine still on with po460 and the gauge is still below empty. Check all fuses. What next? I'm stuck. Is there a way to test the wiring at the tank? They all look ok.
Help!

FireRanger · #6 04-08-2011, 05:41 PM

Quote:

Originally Posted by FireRanger

Pegged full is a direct short to ground. Pegged empty is broke open circuit. What you describe sounds like the wiring to the sender is fucked. Unless you have messed with things nearby, it is probably at the top of the tank.

So short the wire and see if the gauge moves.

sisbug · #7 04-12-2011, 10:03 AM

So I shorted the wire and the qauge did move. I can't test it running since the pump and sender is a complete unit, but did get a response from the gauge. I also used a meter and tested the new sending unit and it's working fine. There is some kind of resistor in the wires at the top of the tank and when I test the positive wire beyond that I am not getting a reading. Would it be possible for this resister to be causing my whole issue of the gauge not working?