Fuel tank sender unit 2.7 diesel

[thomas45]

Having the same symptoms as already posted on here, ie erratic fuel guage I am considering the possible mentioned causes. So if it should be the sender unit how is that accessed ?
Of course it could be the guage itself which sometimes reads empty at start up and remains so until next start when it may seem to be working normal or would jump past the full mark.It also makes a springy sort of noise.
At the moment I depend on what the Range reading says for miles remaining and I'm thinking about disconnecting the Battery for a while to see if that would help. ( I suppose there may be other issues as a result, like radio code for one )
Can anyone enlighten me on this ?

[J44EAG]

The fault in the gauge ie the noise is curious.

A hard dump battery disconnect will clear old fault codes and the radio code so have that to hand. A car which has loads of codes sored can cause problems. Hard dump removal is one method of clearing down.

It is well worth buying a scanner to take the guess work out of the equation. The iCarfoft930i at around £90 is one option or if you have an Android phone, the torque paid down load and a blue tooth ELM37 OBD11 plug transmitter is another. I have both methods and the gear is very useful. Use of such equipment avoids having to hard dump by battery disconnection.

The sender unit, pump etc is accessed by removing the back seat squab. You will have to feed the seat belt pre-tensioners through the squab to remove and refit. Two clips at the lower front edge of the seat secure it to the car body.

Mike

[thomas45]

Thanks very much Mike, I havent been on here for a few days. At the moment fuel guage seems to be behaving itself but now the gremlins have decided to move on to another trick.
The reverse parking aid has stopped functioning and i get the single 3 second tone. I have read a few articles in the magazine on this and there is no damp in the boot wheel well.
You mentioned that there could be problems caused by an accumulation of stored fault codes and I think it is likely in this case although I have not had any read. So I think I will disconnect the battery and take it from there. I do have the radio code.
Apart from all that the car is running very nicely having got past the exhaust problems and sorted the warped front disc with a new set and new pads.
Oil and filter service recently done and next to zero in on the fuel filter.

[J44EAG]

Yet again with all things Jaguar electronic, a low terminal voltage or battery instability due to age and general tiredness can cause such issues. Drop test the battery if you have one. A tester is about £35 on ebay and a sure fire way to see how your battery performs under load. One of my most useful tools.

The reversing system gremlin hits again. My car does this from time to time. Usually it is a corroded connection on the sensor units behind the rear bumper that causes this issue. Often pulling the connector of each sensor a few times is enough to reinstate a bright metal connection and then the system settles down again. Access is not easy with the bumper cover in place. Best to employ a child with thin arms for ten minutes and reward with a packet of crisps, an ice cream and a can of coke. Well worth a try.

A defective or inoperative sensor can be found by engaging reverse gear with the ignition on. Each sensor should quietly tick if you put your ear to each one on turn. A non ticker indicates a unit which may be the culprit. Avoid pressure washing those sensors. They don`t like heavy pressure. Iced sensors can also cause issues in the winter if frozen up.

On petrol models the fuel filter is behind the NSF plastic wheel arch liner ie just in front of the front passengers feet. Mounted on a removable bracket, with snap fit connectors. A relatively easy job but others will be better placed to advise on location and methodology for replacement of diesel models.

Mike

Mike

[Martec]

Just to add to the fuel sender electrics, as the fuel tank bottom is raised over the propshaft and exhaust, the fuel tank is treated as two tanks, so there are two senders and the signal (depth) is evened out at the dash unit or rear ECU. As the fuel can slosh from one side of the tank to the other then there is one submersed pump on one side that pumps some of the fuel through an eductor in the other side of the tank to lift and return all the fuel to the space around the fuel pump.

There are two terminal connectors, one on each side of the tank under the big rubber bungs under the rear seat, there is a picture somewhere on here where someone had removed the pump unit and photographed it?

Brian

[thomas45]

Thanks to Mike and Brian for all that very enlightening info. Here is what sorted since ---- I disconnected the battery for an hour and on reconnection the fuel guage worked normally and so all is well there. ( not the sender unit afterall ) However the reverse park aid remained inoperative with just the 3 second tone then nothing.
I will try again as suggested to listen to the Sensors although I have considered replacing them with a complete new kit installation and in the process somehow isolate the original control module.
I see that there is a 5amp fuse for it in the box in the drivers footwell.
Maybe not have to go to that if any bad /corroded connections can be accessed by pulling sensors back from panel ( providing there is enough slack in the cable)
Otherwise too much hassle to have to remove the bumper. and bumper it is as I have already bumped a bit to-day.
Thomas 45