89 L.X. 5.0 gas gauge always points full even with Key out

[revedup]

can ANYONE TELL ME HOW TO TROUBLESHOOT THIS FULL GAS GAUGE READING ALL THE TIME??????
iTS GOT 212,00 MILES AND I BELIEVE ITS ORIGINAL SENDING UNIT THANX ANY AND ALL SUGGESTIONS WILL BE APRECIATED THANX AGAIN

 

[1SLO306]

these cars read how much gas u have even with the key turned off and out off the ignition

 

[monte87]

bad sending unit, no doubt, or the needle is struck in that one position. i would say bad sending unit though. yank that crappy gauge add a autometer and swap the sending unit-and be done with that headache forever, like i did.
Anthony

 

[bullitstang1313]

The only way to really troubleshoot this problem is to drop the fuel tank. The sending units in these cars go bad quite often or at least mine have. The sending unit is just a variable resistor. The more full the tank the higher resistance, often times the sending unit gets an open in the circuit causing the resistance to be infinity hence a full tank. You can check the gauge by hooking different resistors to the wiring. I can't remember off hand what resistance is full and what is empty, but if you can do a search on here; I've seen this on here before.