Fuel gauge fun

[NotoriousREV]

The fuel pump failed on my 1999 C4 a few weeks ago, which I replaced but since then I've had some weird stuff going on with the fuel gauge. It either sticks at a single reading or it goes up to a reading and then immediately drops to zero and the fuel light comes on. I've tried brimming the tank (the gauge stayed at its previous reading of just over half a tank), if tried taking the sender unit out and reinstalling it to check if it's caught up on any pipework inside the tank but no joy (I'm still not entirely convinced it's free floating but it's impossible to really check). Any ideas?

Video

 

[deMort]

On C4 there is a calibration routine that must be done when the pump / sender has bed removed .. this only affects the lower end of the fuel gauge and accuracy though so it won't be that .

Your sender is hitting and catching on the pipes im afraid .

The center part of the top has a triangle on it .. this lines up with another triangle .. you need to check this is correct and also take it apart and look at the position of where the sender rod is in relation to the pipes .. make sure nothing has moved into that area as it's certainly not able to rise up and down correctly atm .

It is possible the sender got damaged or the wiring plug is loose but catching a pipe is closer to what it sounds like to me .

EDIT .. much later ..

Actually after thinking about this some more .. the fuel gauge drop off doesn't sound correct .. check the wiring plug .. if not that then have a good look at the sender .. it might be damaged .

 

[NotoriousREV]

Cheers deMort, I'll have another look tomorrow. I'm 100% the connector is fine, so it's more likely to be the sender itself.

 

[deMort]

I didn't see the video link first off .. it's going to be an issue with the sender unit i feel after seeing that ..... if it catches on a pipe you have say a half tank full reading when its full .. the float is stuck under a pipe ..

the same the other way ..

The fuel sensor is just a potentiometer .. an item that gives a set resistance as it rises and falls .. it shorts out a wire loop on the sensor basically at different heights .. to drop to zero then there must be a dead spot .

To test .. i'm afraid you need to remove it .. you need to clean all fuel off of it .. fire hazard .. connect an ohm meter to each connection and slowly lift and lower the float .. there should be an increase and a decrease of ohms .. any drop off and its dead at that point i'm afraid .