Calbrating the fuel guage?

[Padre Dave]

Greetings and Lenten blessings to all!

I noticed a new and interesting quirk in my '01 PT: The fuel guage will not register full. I had the misfortune of finding this out when the shut-off valve at a pump I was recently using and I ended up wasting some of that expensive stuff all over the concrete and fender. Even when completely full, the guage registers at around 7/8 of a tank.

Is there a way of recalibrating the sending unit or does it need to be replaced? Minor inconvenience, since my recorded mileage is the same using the odometer and filling method.

I have also had 3 occurances of the headlights not coming on when turned on. The brights work fine, the flood/driving lights work fine too. I have tried playing with the switch with no success. Then, inexplicably, the headlights come on and work fine. This only seems to occur when I leave it outside overnight....not a strong correlation, I admit, but I cannot find any other reason for this occurance.

At 126,000 miles, I am on my own and do the dealer thing only as a last resort. Tomorrow my PT goes in to a local garage for replacement of the timing belt, radiator hoses and belt.

Any ideas will be appreciated!

[TomCat]

Hi Padre.

Fuel tanks used to have a float-type mechanism (sort of like whats in a toilet to shut off the water) to send data to your fuel gauge. The float might be restricted in some way from going all the way up. Thats assuming they still use this method.

As for the headlights, if it only happens after the PT has sat out overnight, it sounds like condensation (dew) is causing a short somewhere. Although I'm not sure how much dew you get in Arizona.

These are just wild guesses, I'm sure someone with more knowledge will reply to help you out.

Tom

[QuicksilverDon]

I have had instances where the gas gauge at some fill-ups can go over the F, other times, only 7/8 or so. I regard it as a personality.

I have read of several folks needing a new "multifunction switch" - usually their fog lights wouldn't come on - it's the same switch. You can do a search on the posts here - some replaced it themselves. I guess it could also be a relay, but I haven't read of any of those needing replacing.

I have only 71,000 miles on mine. Other than oil changes, tires, brakes; I had auto fluid changed and put in Champion platinum plugs and better ignition wires. So far, all's well.

[BlueMeanie]

Have you topped off your headlight fluid lately?

Dan

[GOLDMEMBER]

I don't believe that there is a way of calibrating it maybe a bad sensor. I will look into it and see what I can find out

[Dave'sPT]

My only warrenty repair so far was the switch to regualte the headlights. I used my highbeams and then they just would not turn off, the dealer said i multi-switch controls all operations of the lights... they have noticed that these need replacing alot.
Dave

[Overtake]

Originally Posted by Padre Dave

Greetings and Lenten blessings to all!

.....I have also had 3 occurances of the headlights not coming on when turned on. .....

Happened to once!

[PT_Sean]

From the SERVICE MANUAL:

FUEL LEVEL SENSOR
DESCRIPTION
The level sensor is attached to the side of the fuel
pump module (Fig. 2). The level sensor consists of a
float, an arm, and a variable resistor.

OPERATION
As the fuel level increases, the float and arm move
up. This decreases the sending unit resistance, causing
the fuel gauge on the instrument panel to read
full. The fuel level sensor (fuel gauge sending unit)
sends a signal to the BCM and the BCM sends the
signal over the PCI bus circuit to the PCM to indicate
fuel level. The purpose of this feature is to prevent
a false setting of misfire and fuel system
monitor trouble codes if the fuel level is less than
approximately 15 percent of its rated capacity. It is
also used to send a signal for fuel gauge operation
via the PCI bus circuits.

FUEL TANK DESCRIPTION
The fuel tank is constructed of a plastic material.
Its main functions are for fuel storage and for placement
of the fuel pump module (Fig. 3). The tank is
made from High density Polyethylene (HDPE) material.

Could be the float arm, could be that its PLASTIC and the tank is starting to derom- have a look under the PT if you can.

[lisa]

The fuel gauge on my cranberry 01 ltd was kinda goofy-would fill way past the line but when it was empty, it never got to E before it would run out of gas (found that out the hard way!). It was a Canada car so the gauges had been changed out for import to the US.
As for the lights-I think that they replace the whole stalk that the controls are on.

[MX-5]

There a TSB for fuel level faults that was released wayyyyy back in late 2000.

Check with PTdiy.net when it comes back online.