New problem, 88 S15 fuel gauge not working

When switch is off gauge reads empty. as soon as I turn on switch it goes below empty and disappears backwards. Any ideas where to start? checked fuses already. I know there is gas, I filled the tank, no change.

When the fuel gauge indicates below empty, it means there's short to ground in the gauge signal wire somewhere between the dash and the fuel tank. When the signal wire shorts to ground, the fuse does not pop. Has the tank been out recently? Possibly the wire got pinched. If you need a schematic, send me a PM and include your email address in it. I like your signature ;)

Thank you for the reply! I just bought this truck for the body after mine got wrecked. I had to make one out of two and this is all that is keeping me from being satisfied with the results. I don't know if it has been out or not but now, at least, I know what to look for!

Keep us posted with whatever you find. If you have more questions...just ask.

had some good weather and I decided to see what I could find and ....
Found the pink wire was cut and not connected at all....did some tracing and searching and found a short(by short i mean 1/4 inch) wire coming out of fuse block. So I connected the 2 wires together and was thinking, Yes problem solved. Wrong, nothing changed. I checked resistance from pink wire to ground from tank and got nothing.total open circuit. Im thinking bad sending unit? someone had replaced wire to fuel pump at some time, so I dont know if pump was changed or what was done.I do know pink wire from tank is not connected to anything and when I do connect it fuel gauge still does the same thing. The fuel pump wire is connected to fuse box on hot when switch is on. so fuel pump runs when switch is on all the time. Someone did what I call a redneck job on fuel pump. truck runs fine though. So a bad sending unit maybe?

If you check resistance from the pink wire to ground, (at the sending unit), and it shows open, the level sender is bad. I suppose it's possible that when they monkeyed the fuel pump wiring they may have inadvertently connected battery voltage to the fuel level sender, in which case, the windings in the sender would burn up in a very short time and then read open circuit. You may end up running a whole new wire from the sender to the dash gauge.

thanks for the help, looking at 90 dollars for new sending unit. I may check a few local junk yards also. Ill run new wires when I fix it. I will post back if that fixes the problem.

i have a similar problem. gauge shows empty with low fuel light on. when i disconnect the ground at the battery and reattach it the gauge will jump to full, then after a short period of time return to empty. is this a gauge problem or sending unit or grounding issue?

Unplug the wires to the tank and see what the gage does, sounds like the tank unit.