Fuel gauge erratic (common question I'm sure!)

[belugablack]

I know that many 740s suffer with this, but is there a proper cure for an occasionally dodgy fuel gauge, i.e. one that can flick from full to empty and then settle at midway before flicking about again. It works OK sometimes but I am not good at watching my mileage and calculating how much fuel I have probably used.

Is it likely to be the gauge itself at fault, something more complex behind the dash,or a sender etc etc and is it an easy fix?! I have seen quite a few cars advertised with faulty gauges that I wonder why they haven't been fixed.

Has anyone successfully cured theirs please? Is it almost definite to be one thing, or could it be that I get a new sender only to find I need a new gauge, and then maybe it was something else all along type of malady! In which case should I grin and bear it?!

All help gratefully received!

Daniel

1990 745 GLT

[James_N]

I kinda sucessfully cured mine!

Mine simply didnt work when i got it. So i got a second hand fuel sender off ebay and had that fitted by a garage. Then i bought a few fuel gauges. The one worked but flicked around a lot, then i tried another one, and that worked ok.

It does go a bit strange round some corners, but for the most part, it works fine, and was suprisingly accurate when i went to france.

Have a look on ebay and around local scrappies, and get a few fuel gauges, fit them, and see where you go from there.

For me, it was mainly trial and error. The second hand fuel sender i knew worked, so i just had to fit fuel gauges untill i found one that worked ok!

[BillB]

You can test for a sender fault with a multimeter. The sender wires are accessed via the left hand pull-out section in the cargo area of an estate (I forget the colours). Haynes gives resistance values for different tank levels. A reading of infinity ohms (or intermittently infinity) suggests a faulty sender. If it seems OK, suspect the gauge, which typically has dry soldered joints. You have to remove the gauge and investigate. Typically, the printed circuit connections fail or the metal posts that connect the gauge to the circuit. Regards.

[wispa]

The girly and no-tech answer is find a bump or hole in the road and drive over it, that normally sets it working - that's how I work with my erratic gauges! Both fuel and temperature are suspect on mine.

Also - if you don't think you can trust your fuel gauge, why not refill every 250 miles (use your trip meter and reset to zero every time you refill. ) Then you have a way of double checking the erratic gauge.

[James_N]

250? I really struggle to manage that around town with my 2.3 petrol. Dont forget, yours is a diesel, and the OP's car is a petrol

Id say 200 miles to be safe.

[740Estate]

I used to get 250 out of my 740 when it was filled to the brim to start off with, but yeah go with 200 for safety's sake!

[webbie1983]

Originally Posted by James_N

I kinda sucessfully cured mine!

Mine simply didnt work when i got it. So i got a second hand fuel sender off ebay and had that fitted by a garage. Then i bought a few fuel gauges. The one worked but flicked around a lot, then i tried another one, and that worked ok.

It does go a bit strange round some corners, but for the most part, it works fine, and was suprisingly accurate when i went to france.

Have a look on ebay and around local scrappies, and get a few fuel gauges, fit them, and see where you go from there.

For me, it was mainly trial and error. The second hand fuel sender i knew worked, so i just had to fit fuel gauges untill i found one that worked ok!

who fixed it again :P????? I some what remember leaning in the back of it with a full fuel tank and someones mum outside smoking a fag!

[JohnL]

I asked a few ago about my gauge giving faulty readings, it seems now that its back working again correctly! The only explaination I have is that the atmospere is now dry, and all seems to well. Has anybody come across this, I have to find which joint is letting in the moisture, is there a connector close to the tank, I havent had time to look yet.
Glad I didnt go to the expense of changing out the complete unit.
John

[stephend]

Originally Posted by JohnL

I asked a few ago about my gauge giving faulty readings, it seems now that its back working again correctly! The only explaination I have is that the atmospere is now dry, and all seems to well. Has anybody come across this, I have to find which joint is letting in the moisture, is there a connector close to the tank, I havent had time to look yet.
Glad I didnt go to the expense of changing out the complete unit.
John

I get something like that with my speedo. Once in a while it doesn't move off zero until I give the top of the dash a thump! Almost always when the weather's cold and damp. I don't know if the problem's electrical or mechanical.

[deeman940]

Originally Posted by stephend

I get something like that with my speedo. Once in a while it doesn't move off zero until I give the top of the dash a thump! Almost always when the weather's cold and damp. I don't know if the problem's electrical or mechanical.

LOL...I have the same problem! I gave up hitting the dash as I didn't want to damage it! it doesn't bother me most of the time but it would be handy to know the exact speed when going through cameras etc.