Problem with fuel gauge, new LC100

Hi,

I have new, end of 2005 prod, LC100 diesel. The fuel gauge shows less fuel
in tank then it is in really. After each tank refilling, it gradually
indicates less and less fuel, down to 1/4 when it is actually full after,
say 4-5, refillings. The Toyota service dismantled all parts and found
nothing wrong. However, after this exercise, gauge showed correct reading,
but then again after next refueling the symptoms reoccurred. Obviously,
Toyota service does not know what causes that malfunction. Now, they ask to
keep the car for 2-3 days for "observation".
And, I could neglect this problem but the trip info from car computer
display are then absolutely ridiculous and all its warnings that fuel level
is low pisses me off when I know the tank is at least 3/4 full.
I know there is similar problem with Toyota Prius /hybrid/ but those cars
are not alike.
Any guess ?

Jerry

"JK" <jkrz@NOSPAM.pro.onet.pl> wrote in message
news:e0oadm$sju$1@nemesis.news.tpi.pl...[color=blue]
> Hi,
>
> I have new, end of 2005 prod, LC100 diesel. The fuel gauge shows less fuel
> in tank then it is in really. After each tank refilling, it gradually
> indicates less and less fuel, down to 1/4 when it is actually full after,
> say 4-5, refillings. The Toyota service dismantled all parts and found
> nothing wrong. However, after this exercise, gauge showed correct reading,
> but then again after next refueling the symptoms reoccurred. Obviously,
> Toyota service does not know what causes that malfunction. Now, they ask
> to keep the car for 2-3 days for "observation".
> And, I could neglect this problem but the trip info from car computer
> display are then absolutely ridiculous and all its warnings that fuel
> level is low pisses me off when I know the tank is at least 3/4 full.
> I know there is similar problem with Toyota Prius /hybrid/ but those cars
> are not alike.
> Any guess ?
>
> Jerry
>[/color]

The fuel gauge sender and low fuel level warning light on the fuel gauge are
different devices that work on different principles. When you mentioned
that you are getting low fuel level warnings, I assume you are talking about
the trip computer function and not the low fuel level warning light on the
fuel gauge.

The fuel gauge sender is basically a float attached to an arm that rises and
falls with the fuel level. The arm is attached to a rheostat that varies
voltage to the fuel gauge. For example, if the arm were attached to the
volume knob on a radio, the volume would go up when the tank is full and go
down when the tank is low. If the fuel gauge sender is not moving freely,
the float has a hole in it, or if the rheostat is not calibrated properly,
the fuel gauge could read incorrectly. Two other possibilities are too
much resistance in the circuit between the fuel level sender and the fuel
gauge itself or a bad gauge.

The low fuel warning light on the fuel gauge is a sensor that closes a
circuit when it is dry because the fuel level is below it and opens a
circuit when it is submerged. When the circuit is closed, the light on the
fuel gauge comes on.

Since the fuel gauge worked properly and gradually got worse, my guess is
the float is taking on fuel and gradually sinking, and when the service
department took it out to check it out, they dried it out and the process
started over again.
--

Ray O
(correct punctuation to reply)

I don't know about your Toyota, but my BMW 3 Series had a problem that was
similar, the tank would go to E, but remain there after filling. While
driving, the needle would decide to rise to the appropriate reading, then
eventually display E again and hold that after filling. Eventually, it fell
to E and stayed there for several refills. I took the Fuel Level Sending
Unit out and cleaned the contacts, now the guage works fine.

A significant difference in my car and yours -- aside from the differing
makes -- is the age, my BMW is a '94. The crap that polluted my sending unit
took several years to build up on the contacts, I can't imagine your car has
the same problem, but it might be worth a look-see ...



"JK" <jkrz@NOSPAM.pro.onet.pl> wrote in message
news:e0oadm$sju$1@nemesis.news.tpi.pl...[color=blue]
> Hi,
>
> I have new, end of 2005 prod, LC100 diesel. The fuel gauge shows less fuel
> in tank then it is in really. After each tank refilling, it gradually
> indicates less and less fuel, down to 1/4 when it is actually full after,
> say 4-5, refillings. The Toyota service dismantled all parts and found
> nothing wrong. However, after this exercise, gauge showed correct reading,
> but then again after next refueling the symptoms reoccurred. Obviously,
> Toyota service does not know what causes that malfunction. Now, they ask
> to keep the car for 2-3 days for "observation".
> And, I could neglect this problem but the trip info from car computer
> display are then absolutely ridiculous and all its warnings that fuel
> level is low pisses me off when I know the tank is at least 3/4 full.
> I know there is similar problem with Toyota Prius /hybrid/ but those cars
> are not alike.
> Any guess ?
>
> Jerry
>
>
>[/color]