hockeyfan935

Hi I have a 1990 5.0 LX and my fuel gauge reads FULL all the time. i need help finding out how to fix it. i replaced the fuel sending unit, tank, and the pump. so far i know that the pink wire from the sending unit is power and black is gound they go up through the trunk and then along the right side of the fender behind the plastic but im not sure where they end up. if you can help me out please place a response.

Dbeck002

have you tried resetting the ECU by unplugging the negative battery terminal for 15 minutes?

hockeyfan935

yeah i tried that and it still reads full all the time. what i also did was turn the key on and i disconnected the harness that feeds power to the pump and the fuel sending unit and the pump stoped working which is normal but... the sending unit still stayed at full. i think it should have dropped the needle down to "E" , its so weird. any other suggestions

Dbeck002

if you turned off all power to the unit and it still reads full than you MIGHT have a faulty gauge but thats speculation. has it ever showed any other reading besides just full?

nemethjames1

sounds like you need a new gauge.......... i gotta cluster outa my 88 with a broken plastic cover i dont need

hockeyfan935

the only time it reads somthing else other than full is when i let the car sit for a while and then i start it up. the gauge reads 3/4 tank then climbs past "F" and stays there then after it sits it settles back down to "E"
please post more suggestions!!!!!

nemethjames1

i would say just unhook the fuel gauge from the wiring harness and see if it changes... either way takin er apart is what your gonna need i'd bet

hockeyfan935

i looked at my diagram and i pulled fuse 18. when i did this the voltage gauge droped to zero and the fuel gauge stoped climbing but did not set to where the current fuel level is.but when i put fuse 18 back in the voltage gauge reads charching system voltage again and the fuel gauge pegs past "F" what im not sure of is wether not i have a magnetic fuel level indicator or a Bimetal fuel level indicator

nemethjames1

sounds like a wire grounding out.... try runnin your own wire to the sender.. might sound hard but just do it to see if it reads correct

hockeyfan935

actually what i was looking into was the (IVR) the instrument voltage sensor or the anti slosh module. both connect to the instrument cluster.
the power and ground wires are good because when i pulled fuse 18 it did what it was supposed to do which was drop the volt gauge and freeze the fuel gauge.