issues with fuel gauge

[superu]

My feul gauge has read wrong for, mmm, 3.5 years.

So it reads full when full, but goes down WAY too fast, i.e. reads 3/4 full after driving 60 miles...

I've had a dealer tell me that with an Ohm meter, the fuel sending unit is bad and not sending correct signals. They said its under the rear, passenger seat and should be cheap to replace. The Chilton says the car doesn't have and in-tnak fuel pump.

I've replaced the pump, float, sending unit assembly from one out of a '98 OB, but same problem..

So I think, WTF?

I just want the gauge to read more accuratly, and i'd like the low-fuel light to come on, (I know it has one, i saw it once 3.5 years ago

I've been running from miulage rather than the gauge for about 3 .5 years and I'd like it fixed..

 

Ideas, suggestions?

[johnceggleston]

this is a common problem. there is a chance that techron fuel treatment will help. make sure to get the one that says on the bottle something about fuel guage or sending units.

 

others will know more, but i think part of the problem is that there are 2 sending units (edit: the gas tank straddles the rear drive shaft, it has 2 sides), one on each side of the fuel tank. the second one may still be bad.

 

i think what happens is that they get dirty and don't transmit/ or send the correct information. mine 97 OBW reads empty @ 200 miles. but will drive 320 on the hiway before the lioght comes on.

 

my son is driving my 95 leg at college. it sat for a year waiting for a replacement treans. before it sat the guage was good, perfect. after the sit, it didn't work at all, didn't budge from E. i ran some techron thru it and it started working intermittenly, did it again and now it works like my 97OBW, E @ 200 miles. we use the trip counter and the light to guage empty. FYI: it's a 15.9 gal tank.

[Kilroy]

Same thing with my '90 Legacy, it worked great until a few months ago and then it started going down twice as fast as usual. I just wait until I am at ~500 km. on the trip meter and then I fill up.

 

I'll look into that additive trick, it might just fix this problem.

[Manarius]

Not even worth your time to fix. Odds are, you'll never fix it. Well, you'll fix it and it'll break again. Might as well just go by mileage.

[superu]

Got it licked!

Running some techron is always a good idea for fuel tanks!

 

So once I got into the fuel gauge issue, I varified what the previous delaer had told me, and what johnceggleston indicated as well...

 

The saddle-bag fuel tank has two sending units. The main (passenger side) and sub- (driver side). I'd replaced the main, and the sub- was still (and was the main problem as per the dealer) bad, I replaced the sub-sending unit and the gauge works well now, reading on E at around 280-300 miles. I still didn't see the light come on, when I filled up with 13.5ish gallons, but I'm pretty sure there is a light

 

Thanks all, and note to self....

bad-reading fuel gauge could be a bad sub-fuel sending unit, located behind the rear seat, driver's side, through a circular (as opposed to oval for the main sending unit) access panel.

 

-mw-

[e4620]

Its a common problem, the fuel gauge in the tank is an open potentiometer printed on a little ceramic board, after living in gas for a while and constantly going up and down they wear out. My old 1990 legacy had the same problem, easily fixed with two new floats from a junkyard. (Theres one on each side of the tank) Lasted another 2 years with no sign of failure when I got rid of the car, only cost about 15 bucks and a few minutes of work.

[Legacy777]

Yeah....if you've replaced the main fuel pump & sending unit, and you still have problems, you need to replace the gauge sending unit on the driver's side as well. The combined resistance is what gives the correct fuel reading. If one is messed up, it can play havoc with the gauge. I had this happen with my legacy. Ended up replacing both sending units.