Technical Fuel gauge problem

[Cinq999]

I've had a diesel leak on my 05 MJ for a little while. Only when full, and found it was leaking from a tiny pin prick hole in the plastic.

So I bought a second hand tank and sender unit complete, which I fitted this afternoon.

I've now got an odd fuel gauge issue.

When the tank was just under 1/4 full, the gauge showed just over half.

I turned the engine off, then on again, and the gauge showed full.

As I was driving to the petrol station, I had Torque running, and it showed fuel level slowly dropping from 98% down to 82%, then rose back up to 96% (mirrored on fuel gauge).

I filled up the tank, and then when I started the car, the gauge showed just under 1/4. As I drove home, the level kept dropping and dropping, and now it's on 0%, despite a full tank.

Has anyone got any ideas?

 

[09 johno]

is it the original fuel sender or the second hand one?
check the earth connection

 

[Cinq999]

It's the second hand sender, which makes me think it's the problem.

Where is the earth connection?

I've got the plug on too of the sender with 4 wires, 2 for the pump, 2 for sender. The wires are wrapped up, and come through grommet in boot floor, down along the side of the interior trim into engine bay.....no sign of a separate earth.

I know after 300 miles it should be down to around 1/4 tank, so I'll wait until then, and take the sender unit out.

A side effect I've noticed before, and definitely now, when the fuel light comes on, the engine power is slightly reduced. Must be to try and save some fuel.

 

[Cinq999]

Problem solved.

Took the sender unit out, and found the float unit dangling. Obviously come unclipped and was floating in the tank.

Another job done!