Rover 75 Diesel fuel gauge issue
 

Hi everybody
Ive started noticing my fuel gauge is fluctuating from sometimes 3/4 full next time driven only half full then sometimes 1/4 tank ,I was wondering if it was a common fault ? maybe the float has a puncture and filling with Diesel ? anything else i can check before i remove seat to investigate.
many thanks julian

Hi Julian,

If you search the forum you'll find an investigative thread by a member who discovered a worn section of the float rheostat on the fuel pump side.

This fault occurs rarely but when it does it's always on a diesel. Perhaps that's because so little fuel is consumed therefore the contact remains in one position for an extended period of time and slowly erodes the track.

Simon

Hi Simon thanks for the info just trying find the thread any idea who wrote it or title to give me a clue im finding loads of threads but not the one you mention.
many thanks

Put---Rheostat Wear---into the search feature at the top of the page.

With thanks to Jon the author was Sonic ZS and here it is.

Simon

Just to compound the wandering fuel gauge issue, worn rheostat 'windings' is clearly a big part of it, but there appears to be more subtle effects related to the state of the engine at the time.

For example, in 2014 BigRuss noted:

The fuel gauge and range on the message centre don't give an accurate reading until the engine temperature increases and the temp gauge reaches the 9 o'clock position. Don't ask for an accurate explanation, but my guess is the gauges are stabilised with regulator circuit. For those that don't believe me, give it a try. Look at the range from cold and again when warm. Applies to both petrol and diesel models.

My thought on this is that the current/instantaneous fuel consumption data is used to calculate range (it's all there is to go on). As the engine warms up, the range is rationalised to a more 'normal' consumption figure. However, this begs the question as to how consumption rate is calculated.


TC

It's usually from the period that the fuel injectors are open.

Simon

Hi Julian, I've spent more hours than I care to remember trying to get to the bottom of this common problem (see the link above, thanks Simon :bowdown:).

I will say that I'm 99% sure that your problem lies with worn tracks on one or both rheostats in your fuel tank senders.

Unfortunately, as far as I know these are no longer available new, but it may be possible to swap them across from a low mileage petrol that's being scrapped ? Does anyone know if they're the same ? :shrug:

Many thanks to everybody for helping me find the link and what a great informative link it is Sonic ZS take me hat off to ya for all your hard work , will keep a look out for replacement sometime in the future.
really appreciated all the help now i know whats going on.
cheers julian

Out of interest Julian, what sort of mileage is on your car ?