faulty fuel gauge

martyn brooks

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bury,gtr manchester
hi have a 2004 tdi c5 4b model a6 ..my problem is fuel gauge shows half full when ignition is on/ engine running. when i put diesel in it rises . but when it returns to just below half yellow petrol warning symbel flashes to indicate empy .and when i turn ignition off fuel gauge goes to zero with all other gauges ,,is this a faulty gauge or fuel sender in tank??? has anybody had simular problems or can any body help with some advice or how to fix ?? all advice and help would much appreciated
 
Is that a quattro model ? The quattros have a split chaimber tank(due to the way the go over the propshaft) and as such they rely on a lift tank to supply the main pump with diesel. Chances are that the lift pump does not work and as such the main chaimber gets empty and it flash the warning light even if the other half a tank is full. It will cost you a few quid though: £250 + for the pump, dealer only !
 
had mechanic look at sender unit and he said it looks fine and that i have infact got half at of diesel .so took car for a run and sure enough yellow petrol light lit up and bleeped when it went down to bang on half full on gauge ??? could this still be the sender unit or as mechanic thinks that the gauge is working but the petrol light coming on may be something to do with the ecu which may need reseting with vagcom or simular??? all help and replys will greatly apreciated
 
had mechanic look at sender unit and he said it looks fine and that i have infact got half at of diesel .so took car for a run and sure enough yellow petrol light lit up and bleeped when it went down to bang on half full on gauge ??? could this still be the sender unit or as mechanic thinks that the gauge is working but the petrol light coming on may be something to do with the ecu which may need reseting with vagcom or simular??? all help and replys will greatly apreciated

It's either going to be the sender unit, or the gauge, The sender unit is the easier of the two to change, so thats where i would start.