Fuel gauge help

[aaronmcgreevy]

Hi there, have a little problem with my fuel gauge in the fact that the needle shows full all the time, when i turn the car on the needle goes straight from empty to full, even though the tank isnt near full, would anyone know what would cause this problem and how to fix it

[AMG Merc]

Surely a wiring/earth issue? Others will be along to post up more detailled comments soon...

[sean_goodman]

aaronmcgreevy said:

Hi there, have a little problem with my fuel gauge in the fact that the needle shows full all the time, when i turn the car on the needle goes straight from empty to full, even though the tank isnt near full, would anyone know what would cause this problem and how to fix it

could be a faulty sender or short in the wiring, if it was me i would try and find the cable which connects to the fuel sender unit at the tank, unplug it.

if it still shows full, faulty wiring or guage
if it drops down, faultly sender.

cant say with out going home and looking at mine where the sender is on the tank but shouldnt be hard to find

[MrCredit]

The fuel gauge works on resistance.
The gauge measures the resistance at the sender and depending on the level of fuel a different resistance is measured, ie no resistance for a full tank and high resistance for an empty tank.
If the White/Green wire is disconnected from the gauge it'll read full all the time.
Sounds like you have a break/disconnection in the White/Green sender wire.

Edited by MrCredit on Thursday 30th April 11:35

[jimbooo]

i thought they all did this. the previous owner had this and fixed it 3 times only for it to go wrong again within a month.

mine reads full and then 1/4 tank when ive done about 230 miles. so it does move but not gradually as it should.

ive never bothered looking at it based on the previous owners experience. i just use the mileage reset button every time i fill up and go by the miles rather than the gauge.