Gas gauge
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Senior User
Joined: Aug 2009
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From: tulsa
Gas gauge
My gas gauge isn't working. It stays on F until I start the truck then it bounces around a little. Where should I start? If anyone has read any of my previous posts you'll know that I'm a fool when it comes to electrical......IS it electrical? This truck sat for 6+ years and started right up after working out a few minor bugs, so I guess I should count my blessings. But then again it IS a Ford.
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Joined: Aug 2009
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I'm just going to throw this out there... but it could be a bad ground somewhere. From what I understand, the gas gauge is basically an ohmmeter, and the float in the tank is a variable resistor. The higher the float goes (the more gas in the tank), the greater the resistance and the higher the needle on your gauge goes. So, if you had a bad ground or possibly a loose connection somewhere, there would erroneously be high resistance.
I don't know if that's correct or even close, but I'm always surprised at how many things can be messed up by a bad ground on these trucks. Last night, my headlights went out because of a bad ground. After cleaning and tightening that connection, my lights are brighter (and actually work), my turn signals work better (used to stop blinking when I stepped on the brake), and my radio picks up more stations (used to pick up only one station in a big city). I treat my truck like I'm flying an airplane. If I'm having problems, I head straight for the ground.
I don't know if that's correct or even close, but I'm always surprised at how many things can be messed up by a bad ground on these trucks. Last night, my headlights went out because of a bad ground. After cleaning and tightening that connection, my lights are brighter (and actually work), my turn signals work better (used to stop blinking when I stepped on the brake), and my radio picks up more stations (used to pick up only one station in a big city). I treat my truck like I'm flying an airplane. If I'm having problems, I head straight for the ground.
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Joined: Nov 2007
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From: Denver Metro Area, CO
In every case I've seen, it has always been a bad sending unit; there is a very
very very very fine wire wrapped around a piece of material (say, similar to a
popsicle stick) inside of the thing, and there's a spring-loaded metal contact
that glides up & down that popsicle stick as the level of gas changes; this is the
varying-resistance mechanism used to supply varying voltage to the dash
meter. In all bad sending units I've seen, that very fine wire breaks and
unravels and floats around *****-nilly and touches the other electrical contact
*****-nilly, making for a totally inaccurate gas gauge. Of course, there are
other possibilities - brass float that fills up & sinks, bad ground - but I've never
experienced anything other than what's described above.
Lead Driver
Joined: Jul 2009
Posts: 6,477
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From: Sheffield, AL
I purchased me truck from an older gentleman who apparently let the truck sit for an extended period of time with a nearly full tank. I say this because the gauge works correctly for approximately 15 miles after fill up and then quickly goes to "E". The tiny wire described by ctubutis must be coated with varnish everywhere except for where the spring-loaded metal contact was resting. I reason this as the wire cannot be broken or it would not work at all. Thank the Lord for resetable trip meters.
I will someday replace the sending unit or try to clean the existing one. I have half-heartedly looked for a replacement (new) and have found that they are readily available for fuel injected v-8 applications, but not so easily found for my 6 cylinder due to mine being carburated and there was a change, I believe, in tank design so that 1985 and 1986 fall in one catagory, thereby reducing the demand for this item.
NumberDummy, can you shed some light on this? Thanks!
I will someday replace the sending unit or try to clean the existing one. I have half-heartedly looked for a replacement (new) and have found that they are readily available for fuel injected v-8 applications, but not so easily found for my 6 cylinder due to mine being carburated and there was a change, I believe, in tank design so that 1985 and 1986 fall in one catagory, thereby reducing the demand for this item.
NumberDummy, can you shed some light on this? Thanks!
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From: NoGa.
Althought it gives you the OPPOSITE problem, the other thing that I have seen on my Fords ... is a bad float.
The old brass ones will get old and crack in places allowing it to fill with fuel and ... well ... NOT float.
I couldn't find a replacement ... but I had a float from an MGB that is a similar shape and size ... so that's what I installed back in the Old Gal.
Eventually I cleaned up the brass float ... located all the splits, holes, and cracks by holding it submerged in a jar of mineral spirits ... and soldered up the holes. Its in my bins of spars now.
oddshot
The old brass ones will get old and crack in places allowing it to fill with fuel and ... well ... NOT float.
I couldn't find a replacement ... but I had a float from an MGB that is a similar shape and size ... so that's what I installed back in the Old Gal.
Eventually I cleaned up the brass float ... located all the splits, holes, and cracks by holding it submerged in a jar of mineral spirits ... and soldered up the holes. Its in my bins of spars now.
oddshot
