Fuel Gauge is erratic on 95 Legacy

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Thierry Lavallée

Fuel Gauge is erratic on 95 Legacy

Post by Thierry Lavallée » Tue Apr 15, 2003 12:36 pm

(Legacy 1995 wagon 4x4. )

Hi all,
The fuel gauge is completely nuts and am wondering if anyone has ideas on
what it could be.

The tank might be at 1/2 and the gauge shows it correctly, then 2 miles
later, it shows a 1/4, then back up at 1/2.

Any ideas?

alan butler

Fuel Gauge is erratic on 95 Legacy

Post by alan butler » Tue Apr 15, 2003 5:26 pm

Sub tank level sender unit, LH side behind rear seat.

Thierry Lavallée

Fuel Gauge is erratic on 95 Legacy

Post by Thierry Lavallée » Thu Apr 17, 2003 8:39 am

alan butler, 4/15/03 17:16 :

> Sub tank level sender unit, LH side behind rear seat.

I'll check it out, thanks.

You mean that I won't need to take the tank off? That would be wonderful
design. Easy to fix?

Thanks again! :)

Thierry Lavallée

Fuel Gauge is erratic on 95 Legacy

Post by Thierry Lavallée » Wed Apr 23, 2003 3:29 pm

It seems 4WD are equipped with a fuel pump/fuel level sending unit(right)
AND a fuel level sending unit(left).

Do you have an idea on which and WHAT could cause the problem of ERRATIC
fuel level information? My problem is not that I don't get info, it's that
the info is unreliable.

Haynes tells to check the resistance than must be between 0-50ohms depending
on fuel level (arm). If the readings are not corresponding, Haynes says to
replace the unit. Is this repairable? Subaru stuff is SO expensive.

Could there be ANY other reason than the fuel level sending unit for having
such problem?

Thanks again!


Fuel Gauge is erratic on 95 Legacy

Post by Everson » Wed Apr 23, 2003 4:19 pm


It's not worth trying to repair!
Subaruparts.com is the cheapest I fount.
Thats my $.02

Douglas Hancock

Fuel Gauge is erratic on 95 Legacy

Post by Douglas Hancock » Thu Apr 24, 2003 4:09 am

WRX Inaccurate Fuel Gauge Fix From MRT http://www.mrtrally.com.au

The WRX has 2 sender units, the one on the RHS incorporates the fuel pump while a similar dome cover on the LHS of the luggage compartment also has a sender unit mounted on the tank, apparently the RHS one handles the lower half of the tank, while the other one on the LHS handles the upper half of the tank.

After lifting the carpet on the RHS of the rear luggage area you will find a dome cover held down by 4 Philip's head screws. Once the cover is removed you will find the top of the fuel pump and gauge sender unit. On this top cover are 3 fuel hoses and an electrical fitting. After removing those and the 8 * 8mm hex nuts the unit is removed with a bit of twisting and fiddling. The LHS unit can be accessed in the same way by removal of the dome cover disconnect the wiring plug and undo the 8mm hex nuts.

The RHS unit is far more bulky than the LHS comprising a fuel pump attached to a strainer bag system, the gauge sender unit is very basic being a plastic float on the end of a wire stem that actuated across a potentiometer. I found that after 4 years the potentiometer had a wear patch across it, so I wiped it down and polished the surface with 800 grit wet and dry, very gently!! After reassembly the gauge read 20% higher.

It seems that after a while the surface of the potentiometer gets a waxy build up or something on its surface from the fuel. The LHS handles the upper levels of the tank, I guess 1/2 to full, while the RHS handles the lower levels of the tank. Again by wiping the face of the potentiometer with a rag and very gently polishing it with super fine wet and dry and reinstalling the LHS unit the fuel gauge worked perfectly again. The tools required are a Philip's head screw driver for removing the baggage floor cover, a pair of pliers for releasing the hose clamps and a 8 mm socket for the hex nut holding the units to the tank. Overall all very easy job once you realise there are 2 of them. Should take less than 1 hr.

After talking to Subaru its a common problem for all Subaru models and is often done on 100,000km services if they suspect a problem. However if the problem returns quickly they end up replacing the LHS sender unit first as it is the cheapest, due to the wear on the potentiometers resistance surface, then worry if the RHS fails as it can get expensive.

In addition by bending the wire that attaches to the float you can fine tune how the gauge reads, ie dead empty can mean dead empty or 5 litres or what ever you require.

For those thinking of installing a fuel surge canister or plate in the tank you will need to fabricate 2 as both the LHS and RHS sender units have fuel pickups. The LHS fuel pickup connects to the RHS sender unit.

IMPORTANT: We must stress that there is a very fine margin between cleaning the potentiometer surface and destroying it! Use utmost care.