BMW 3.18is Faulty Fuel Gauge ???
Ali
cool to watch the tank fill up as the petrol goes in...... anyway, sure
enuff it was satisfying but, soon after filling the thing up, the gauge went
to empty, and that's where it has stayed for about 2 months, and many
fillups of gas...
can anybody give some pointers on how to fault find this... would like to do
it myself if possible ???
help please ?
Scott M
> I broke it i think, we were filling the car up and i thought it might be
> cool to watch the tank fill up as the petrol goes in...... anyway, sure
> enuff it was satisfying but, soon after filling the thing up, the gauge went
> to empty, and that's where it has stayed for about 2 months, and many
> fillups of gas...
Having read about the cure for this fault, I always wondered how people
managed to cause it in the first place as it'd never occur to me to
leave the ignition on while filling up.
Anyway, you need to pull one of the fuses for the dashboard (there's
several) for a few seconds. I forget which but on my '94 325 it's
labelled as "Instrument Cluster", or something similar. Alternatively
disconnect the battery for a few seconds (but you'll radio/OBC settings
if you do.)
That should get it working again.
--
Scott
Where are we going and why am I in this handbasket?
Jeff Strickland
The tank lives under the back seat. Lift the seat cushion out and pull back
the black tarpaper material. this will reveal two (one on the left and one
on the right) covers. Remove these covers and this will expose the sending
units for the fuel level detection. The left side sending unit is simply a
sending unit, the right side unit is part of the fuel pump. You might be
able to clean them with contact cleaner, but most people replace them. You
can check them with a multi meter.
"Ali" <ali...@xtra.co.nz> wrote in message
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Scott M
> You did not break the guage because you watched it.
Oh yes he did! There's a few mentions of it in the archives.
Jeff Strickland
watching it go down. From the perspective of the circuitry, there is no
difference. If the guage is going to break because the key was on when the
tank was filled, then it would break as the tank empties.
"Scott M" <smorris_12@delete_this.yahoo.com> wrote in message
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Ali
back seat left hand side. still no go. I have pulled the fuse and
dissconected the battery. still no go.
Any new ideas, it seems the gauge it's self looks ok, the empty light glows
and the neadle moves like 0.5mm when the key is switched on. It's like it
fails the initilizing process, cuz the temp gauge and the pertol gauge used
to do the same thing but now the petrol one just stays on..
Any new ideas will be greatly appreciated..
Ali
"Scott M" <smorris_12@delete_this.yahoo.com> wrote in message
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Scott M
> I can not understand how watching the needle go up is any different than
> watching it go down. From the perspective of the circuitry, there is no
> difference. If the guage is going to break because the key was on when the
> tank was filled, then it would break as the tank empties.
And I agree! I couldn't, and still can't, understand why there's a
problem and why it doesn't die in the normal course of things, but it
does! I had a similar problem with my fuel gauge. The morning after
brimming the tank the gauge stayed at the bottom (it had worked fine on
the way home.) I checked the resistance of the senders, pulled the
connectors etc, but everything was fine and it still didn't work. In
desparation I remebered about the fuse thing having read about it as a
cure for this fill-up-with-ignition-on-problem and lo-and-behold it came
back to life.
I can only think, that as the BMW instrument cluster is more complicated
than the usual milliammeter approach there's something Too Clever By
Half going on.
Scott M
> thanks heaps guys, i have cleaned the contacts to the sender unit under the
> back seat left hand side. still no go. I have pulled the fuse and
> dissconected the battery. still no go.
Next thing is to measure the resistance of the two senders. Pull the
plugs off and check that the resistance of each is within spec (250 ohms
resistance full and 10 ohms resistance when the tank is empty). If you
haven't got a test meter try putting a 220ohm resistor in place of each
sender and seeing if the gauge works then.
> Any new ideas, it seems the gauge it's self looks ok, the empty light glows
> and the neadle moves like 0.5mm when the key is switched on. It's like it
> fails the initilizing process, cuz the temp gauge and the pertol gauge used
> to do the same thing but now the petrol one just stays on..
Tell us more about the previous time this happened...
Jeff Strickland
My guage intermittantly dies nearly every time I fill the tank. I can fill
the tank and the guage will either respond or not. If not, then it might
respond in an hour or so, or maybe the next day, or maybe not until a
subsequent fill up. The stealership parts guy said the gas can coat the
contacts on the sending unit and lead to a very high resistance on one of
the two senders. The senders are wired in parallel, so if there is high
resistance on one, the effective resistance on the circuit is cut in half,
or some such thing. The result is that the guage gets stuck on E. If the
trouble is truely a problem caused by a coating from the fuel on the
contacts, then something like carb cleaner ought to clean the coating off.
"Scott M" <smorris_12@delete_this.yahoo.com> wrote in message
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