Fuel guage stuck on full, but returns to zero with engine off. Will red light work?

[Charlie0]

Hi there,

I've got a 2.0 Meridian diesel HDI (2000). The fuel gauge is stuck on full, but returns to zero when the ignition is off. I've been told the red light for a low tank is a separate circuit, so should still come on when I'm low on fuel. Obviously I'm a little apprehensive. I was thinking of carrying 5 litres of diesel in a just incase, although will it damage the car if I run empty or will the engine shut itself off before doing any damage?

I filled the tank to the brim and the problem started after that. Is this just a coincidence or is it possible to get the float arm stuck or something? Would there be any merit to completely filling the tank again or trying any fuel system cleaner?


Many thanks!

[cully]

lift the rear bench seat, lift the carpet, remove the block stopper to expose the fuel tank sender, give the top of the tank a few light taps to see if it frees off.
if that dont help unplug the electrics to the tank, turn on the ign, check the gauge, it should be low with light on, if it still high probably dash clocks goosed

[pug306driver]

If you brimmed the tank you should be ok for 600 miles, but to stay on the safe side, top up at 500, and still carry some spare ful;e at least untill the problem is sorted.

If it where mine, i would travel 500 miles, then remove the tank sender/pump and look see, but after burning off some fuel, say 300 miles, give the top of the tank a good tap, to free a stuck float.

Cannot remember but a wiring diagram would help, low resistance for an empty tank or a high one.?????

[Charlie0]

Disconnected the electrics, red light came on when i switched on the ignition, needle stayed at empty.

Attempted to pull the sender unit out but couldn't get the black ring out with the tools I had, way too stiff. I thought maybe just taking out the sender unit and putting it back in may sort the float out if its stuck, I gave the unit a good few taps!

It's done something, I now notice after 15 minutes driving the fuel gauge starts to move down from full, not as far as I'd expect but somethings definitely happening, so I think for now I'm going to give it time and see if it fixes itself!

[Mighty306]

If it's a replacement sender unit it is possible it's been installed with the float too close to the side of the tank. Loosen off the locking ring using a hammer n chisel (or targe flat head screwdriver) on the tabs to get it started. Once loose just try rotating the sender unit a few degrees clockwise in the first instance. No need to remove the sender n doing so is likely to be messy. (Difficult to do without spilling fuel inside the car).

[pug306driver]

Use a very blunt screw driver, or very instrument as you dont want to break the screw rim. I have to say when I removed the pump/sender unit on our estate i did not spot the alignment arrow/mark.

If fitted incorrectly the float can float can foul the tank wall, and even sit on the shelf inside the tank giving a false reading.

If the float was sticking some taps on the top of the tank would free it i would have thought.

How long has it been doing it, just after you brimmed the tank ?

Has the pump/sender unit been out of the tank before ?

[Charlie0]

Fuel gauge is fixed! Seems that tapping on the unit fixed it. Fuel gauge has been working properly for a few days now. It was temperamental for a few drives after I tapped the unit, but worked as normal once the tank got below 3/4 full

pug306, not sure if the pump has ever been out of the tank before, owned the car for about 18 months.