fuel gauge mystery

[Al75]

I recently picked up my new Rover 75 1.8 petrol, its in very good condition. Its only done 31000,it has been locked in a garage for 8 years. I had to do a few minor jobs, as a result of the cars long sleep. There is one issue which seems odd. When I picked the car up, it had 3/4 tank of petrol, probably old but it drove Ok. As I drove the 200 mile back, the petrol gauge came down as it should. It was at 1/4 on the gauge when I got back. Next day I filled the car up but the gauge stayed at 1/4 full. As I drove the car it came down to empty and the light came on as per normal. Now its stuck on empty no matter how much fuel is in it. Has anybody any thoughts as to the cause?
Thanks in advance.

[Matt_75]

Hi Alan,

Congrats on the new car. The 75 has an inbuilt diagnostic mode that can be used to test the gauge cluster is working, including the fuel gauge (see steps a to h and section 2):

https://www.the75andztclub.co.uk/for...ad.php?t=55585

Use this to test that the problem doesn't lie within the gauge itself.

[vitesse]

Previous poster responded while I was typing but test the level sensors too.

A strange case, but I’m wondering if the old petrol can be responsible. I know the old stuff really stinks, and my old BSA likes a drop of fresh petrol before running well, but you have two level sensors, one on each side of the petrol tank. That one sensor should fail happens, but two at the same time?

I’d start off activating T-Cut’s OBD diagnostics guide and see a) that the fuel gauge is working b) what signals if any do the sensors provide? (https://the75andztclub.co.uk/forum/s...ad.php?t=56450 post 5)

Good luck

[Matt_75]

I've seen a couple of posts recently on cars that have stood for a while and have had trouble with the fuel sender assembly wiring disintegrating:

https://www.the75andztclub.co.uk/for...d.php?t=324031

https://www.the75andztclub.co.uk/for...=304434&page=2 (post #17 onwards)

Your fuel pump is still working so hopefully this isn't the issue. There's a related 'How To' here but the photos are missing:

https://www.the75andztclub.co.uk/for...d.php?t=194156

If you decide you want to inspect the fuel sender assembly, there's some useful photos and instructions on this diesel fuel pump replacement 'How To' (process to access the sender is the same for petrol and diesel):

https://www.the75andztclub.co.uk/for...ead.php?t=4512

[Al75]

I perhaps should mention the fuel pump had packed up and a new one fitted prior to the car being sold to me.
Thanks