PINTO CAR CLUB of AMERICA

Welcome to FordPinto.com, The home of the PCCA => General Help- Ask the Experts... => Topic started by: caravan3921 on June 05, 2021, 12:22:43 PM

Title: Gas gauge
Post by: caravan3921 on June 05, 2021, 12:22:43 PM
The gas gauge appears to be acting unreliable lately.
Seems to always be stuck at 3/4 full when it should be going down.
Filled it to full yesterday and drove it home 2 blocks away and it was at 3/4.
What would the experts do?
Thanks!
Title: Re: Gas gauge
Post by: Wittsend on June 05, 2021, 02:54:57 PM
Likely it is a sinking float, or there is varnish on the sender resistor. I don't know if the floats are available but it isn't too difficult to remove one (the float itself and a length of the arm it attaches too) from a junk yard car and adapt (solder) it to the existing arm. And by that I mean solder a portion of  metal arm that holds the new-er float to the existing arm, not solder the float itself  - which today is likely plastic.

Varnish can be removed often by scraping it but be careful not to damage the wound wires on the resistor.
Title: Re: Gas gauge
Post by: oldandcrotchety on June 05, 2021, 05:10:05 PM
I don't know if Pintos used them, but a lot of the old fords had a resistor behind the fuel gauge that would go bad.  When it does go bad, the gauge will read 3/4 tank when it is really full, and then run out of gas with the gauge showing 1/4.  I had that happen on my '64 ford pickup and also on a 1970.  They are real easy to replace, but as I said, I have no idea if were used on the Pintos.
Title: Re: Gas gauge
Post by: Mattb on June 05, 2021, 06:27:55 PM
Based on the picture of you car looks like you have a 77 or a 78.  For those years in my experience the Pinto and Mustang II used the same sending units. If you go to Spectra’s website and look at their e catalogue they list sending units for the Mustang  II.  You would probably want the FG 179B( I believe that is what I used). It has a second pipe for a return line. The V8 Mustang II  did not have a return line. It appears the 179B is not available right now. The 1976 cars use a FG 178B which looks like the same dimensions but has a slightly different Ohm range( 85-10 vs75-10).  When I pulled the tank we actually put in a new tank as well along with new rubber parts. Just something to consider. Best wishes.
Title: Re: Gas gauge
Post by: LongTimeFordMan on June 05, 2021, 08:57:01 PM
i think the "resistor is actually a voltage regulator to regulate the instrument voltage at 6 volts.

the oem ones had a system like a turn signal flasher that turned and off. there are also new style electronic ones avaialble.

but your problem seems like it might be the sending unit.

you can also test the resistance of the sending unit.. it should range from 10 ohms full to to.70 or 80 ohms empty (see the above post ) as the level in the tank

if the.resistance of the sending unit changes with the level, the problem could be the voltage regulator.

inpostes a post about building and calibrating an electronic regulator here awhile back.
Title: Re: Gas gauge
Post by: PintoRoyL on September 19, 2021, 08:09:41 PM
Hello,
I am about to replace the fuel tank in my '74 Runabout, I want to get a new fuel sending unit. I understand that the 178B mentioned above will also fit in a 1974 Mustang II (according to RockAuto). Do you think it will also work for the '74 Pinto? (RockAuto does not list a fuel sender for a '74 Pinto)
Thank you.
Title: Re: Gas gauge
Post by: Mattb on September 20, 2021, 02:04:30 PM
Based on my experience with my 77 if the fuel tank you are using works for a 74 Mustang II then the corresponding sending unit will probably work as well. You could pull the old one out and compare to the pictures. Are you using the Spectra F80A tank?
Title: Re: Gas gauge
Post by: PintoRoyL on September 20, 2021, 06:42:56 PM
Does Spectra make a new tank for Pintos? I am going to use the old original, I see nothing wrong with it. When I removed the tank several weeks ago, I emptied the old "gas" that was 25 yrs old, and after everything dried out, I stuck the hose from my shop vac in to get the debris that I was unable to shake out through the fuel inlet hole. Since the sending unit mounts low in front, I went ahead and reinstalled the tank without the sending unit installed. I took a chance and have already ordered from RockAuto the Spectra FG178B unit mentioned in an earlier post. RockAuto does not list a sending unit for a '74 Pinto, but says that the FG178B will fit a '74 Mustang, so I will give that a try.
Title: Re: Gas gauge
Post by: Mattb on September 20, 2021, 07:57:38 PM
Well the Spectra F80A is listed as being for the 75-76 Pinto and the 74-76 Mustang II so not sure if the 74 Pinto tank is different from the 75 or different from the 74 Mustang II tank. Sounds like you have a usable original but if issues arise could try the F80A( or have your tank restored). Let us know if the sending unit works out.