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MG MGF Technical - Fuel gauge inaccuracy

We now have an MGF in the household. Early 1.8i on an N plate. Has one little niggle though. After brimming the tank the fuel gauge only went to half way. Done 150 miles and its gone down 3 notches, which isnt bad. Is this a known problem, and is there a cure?


Gareth Kidman

Gareth, Two possiblities come to mind.

1: Faulty fuel tank sender unit. (worn wire wound resistance component or contact?)
2: Faulty fuel gauge.

If you're taking out the fuel tank sender unit strictly adhere to safety practices....
Disconnect battery before any work with tank.
Work in a well ventilated area.
No flames or pilot lights near by,
No smoking.
And Don't use any matches to look down the tank...OK You wouldn't do that, but there are stories around... :-)


Thanks for the reply. Where exactly is the sender unit to save me looking?
Gareth Kidman


The sender unit is accessed by removing the rear shelf carpet which covers the engine bay area.

If you stand behind the car facing to front it is on the left side. There is a large round cover plate held down by 4 screws.

The fuel level sender unit is an intergral part of the fuel pump assembly.

If you intend to DIY, I would suggest to have access to the workshop manual to guide you as you need to depressurise the fuel system etc, etc.



Just checked it, i can see someone has fiddled with the wires in the past. I also seem to have a wire with a white multiplug in the middle, terminating in two spade connectors, one black, and the other black/green. This is on the NS of the car underneath the carpet cover. Any ideas as to what it is?
Gareth Kidman

It's almost the swimmer position (circular angle) and depends on how the sender unit is mounted.
Some get sticky at the inner sidewall, but this is known from cars with replacement tanks only. Serveral got replaced due to fuel smell troubles about 5 years ago.

image of the fuel tank

Notice, the adjustment or fuelpump replacement is one of the worst and difficult DIY works. Assume the workshop had given in if the tank got replaced.

Dieter K.

As our's is an early one (95), sounds like there is a chance the tank has been replaced in the past, and as a result, incorrect fitment of the float/sender unit?
Gareth Kidman

I think so. In case the fuelpump got removed at any time.
There might be a chance to correct this by turning the whole unit some degrees out of the centre line.
Turn right, so that the swimmer doesn't get stuck at the wall on the left.
So far the theory. In live it's much more difficult, cause there's a big cone shape rubber hose gasket between the white pump body and black tank plastic.

Just searched on my own HD archives and found images of the _cut_ item ...
from a former MGF owner and I secured his images on my HD before he unfortunately closed down his website 3 years ago.
Added some more stuff and here we go.

PS. please register your good old car at :o)
Data get kept secure and confident.
Dieter K.

errr ... register at this link ;)
Dieter K.

Wow, thanks Dieter, thats exactly what i'm looking for. I think our's is slightly off in this case. I did refill the tank today until it cut off and got the gauge to 3/4's full..
Gareth Kidman

Then you have two options.

Repair or ignore.

... I'd take the latter ;)
Keep an eye on the done mileage and refill early enough.

Up to you.
Dieter K.

This thread was discussed between 23/04/2005 and 26/04/2005

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.