VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 INACCURATE GAS GUAGE

MY GAS TANK IS ALMOST FULL, YET THE NEEDLE REGISTERS ABOUT 1/4 TANK. wHEN I GOT THE CAR THE GUAGE WASN'T WORKING. THE PROBLEM WAS THAT THE TERMINALS ON THE GUAGE WERE REVERSED. AS SOON AS I SWITCHED THE WIRES IT SPRUNG TO LIFE.

HAVING SAID THAT, I'M ASKING IS THERE IS SOME TYPE OF CALIBRATION THAT CAN BE PERFORMEND ON THE GUAGE. I HAVE A DIGITAL METER AND CAN MEASURE THE VOLTAGE COMING FROM THE SENDING UNIT. BUT BEFORE I JUMP TO CONCLUSIONS I'M WONDERING IF CALIBRATION OF THE GUAGE IS POSSIBLE.

ANYBODY KNOW?

GOTTA31

There is an OHM's reading but...Sorry this may not answer your question but my 38 Master had guage problems and I had the sender rebuilt, and it works great. I have a 93 Dodge Dakota, a 03 X Type Jaguar, my daughter has a 93 Bonneville. None of the fuel gauges are as accurate as my 38.

Check the float on your gas tank sending unit. It may be losing buoyancy. Also, the float arm on the sending unit might be sticking as well.

You can also test the accuracy of the sending unit with an Ohm meter.

I thought that something might be wrong with the sending unit or some part of it(float).
Please don't tell me the only way to check it is to drop the tank and pull it out!!!!!!!!!

:( :( :o :( :(

I thought that something might be wrong with the sending unit or some part of it(float).
Please don't tell me the only way to check it is to drop the tank and pull it out!!!!!!!!!

Okay, I won't tell you that......but that is what you will have to do if you want to check the sending unit arm, the float and the accuracy of the unit.

Hey MACHB:

With the OHMS scale you can only check continuity in the wire. Since the guaage works, I know I have continuity. The sending unit decreases or increases the current by very small amounts. This change in current then passes through the gas guage and the needle moves according to the change.
I think JYD is sniffing in the right place but I just don't wanna hear what I'm afraid the "DOG" is gonna say!!

GOTTA31

DOGGONIT DOG!!!...I TOLD YOU NOT TO TELL ME THAT!!!

wOULDN'T IT BE EASIER TO TAKE A CAN OPENER, MAKE A HOLE IN THE BOTTOM OF THE TANK, STICK YOUR HAND UP IN THERE AND FEEL IT THE FLOAT IS WET???

The Ohm meter can also take the place of the gas gauge when testing the sending unit. When the Ohm meter is attached to the sending unit, you can raise and lower the sending unit arm and the Ohm meter needle should go up and down with the movement of the arm if the sending unit is working correctly.

The float is supposed to be wet....it is sitting in gasoline! Bow Wow!

Yeah, the sending unit is a simple variable resistor circuit, however the way the gauge works is not a simple resistor circuit, the change in resistance changes the potential of the coils on either side of the needle and that small current change works the guage without having to apply a 6 volt current into the fuel tank, for safety reasons.

OOPS! a:confused:

A few years back for a short time when they were using gas that I believe had alcohol in it here in upstate NY, my gas gauge started reading about half the amount in the tank. I think that years ago schellac was used to help seal the cork and the alcohol removes it and it has lost about half its bouyancy??? I got use to it and didn't bother pulling the tank yet. :confused:

Doug might have something here. I've been thinking I would replace the cork with a new one.

Or make sure all grounds are clean!

HEY YOU GUYS.....THANKS FOR ALL THE HELP. THIS IS RARE OCCURANCE, BUT I FILLED THE TANK ALL THE WAY UP AND ABOUT 10 MINUTES LATER, THE GUAGE WENT ALL THE WAY TO FULL. I GUESS THE ARM NEEDED MORE GAS IN THE TANK TO SLOSH AROUND IN, GET LUBRICATED, AND THATS IT.

BY THE WAY, SOME OF YOU ASKED TO REPORT ON MY CLUTCH INSTALLATION. SO HERE GOES.AS I STATED EARLIER, THE PRESSURE PLATE HOUSING HAD A CRACK IN IT SO I FOUND ANOTHER AND INSTALLED IT ALONG WITH A NEW THROWOUT BEARING. THIS HELPED ALOT BUT MY PROBLEM IS NOT COMPLETELY SOLVED. THE GEARS STILL GRIND BUT NOT AS BAD. I'M THINKING NOW THAT MAYBE THE SYNCHRONIZERS IN THE TRANNY ARE WORN. ANYBODY OUT THERE GOT ANY THOUGHTS ON THIS??

GOTTA31

If that is a 31 tranny there are no synchronizers to go bad.

O.K. WHERE WOULD YOU LOOK NEXT, WOODY?

THANKS.

GOTTA31

Yes, the cork floats were coated with shellac.

The sending unit can get really scaled up and cause the armature not to work. Mine actually froze and would not move. I had the old unit rebuilt, checked it with an OHM meter and reinstalled.

I WOULD LIKE TO ASK ALL YOU GUYS OUT THERE.....

WHERE ELSE WOULD YOU LOOK FOR THE PROBLEM OF TRANNY GEARS GRINDING DURING SHIFTS? NEW PRESSURE PLATE AND THROWOUT BEARING INSTALLED AND CLUTCH PEDAL ADJUSTED FOR 1/2" FREE PLAY. SINCE WOODY SAID THERE ARE NO SYNCHRONIZERS IN A 31 TRANNY, I'M AT A LOSS TO EXPLAIN THE PROBLEM. ANYBODY GOT ANY SUGGESTIONS??

GOTTA31

Maybe you are not "double clutching" correctly?

:confused: :confused: :confused:

It is only necessary to "double clutch" when down shifting. Shifting up through the gears, it is normally only necessary to move the shift lever into the neutral position, hesitate for a couple of seconds and then shift into the next gear. If you want to engage and release the clutch when in neutral (double clutching) it is ok but not normally necessary to make a grind-less shift.

What I discovered today is that IF I DO double clutch when shifting from 1st to 2nd to 3rd the grind is greatly reduced or doesn't even occur. However, once I'm in 3rd, if I have to slow down enough so that I have to downshift to 2nd, there ain't no way its going to go into 2nd. If flat refuses until I slow down almost to about 5 to 8 mph. So I'm thinking SOMETHING still ain't right. I just don't know what that SOMETHING might be.

Has anyone out there ever had this problem? If so,
what did it take to fix it?

Gotta31

When you downshift, you have to rev up the engine to match the speed of the car in the lower gear.

Did you check out the pilot bearing?

If there are no synchronizers, it seems double clutching would be required always. As chipper says, you don't have to goose the throttle going up because the new engine speed is lower than the previous speed.