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Gas gauge reading on Instrument panel, 66 Fairlane

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berry32ford
Junior Member


Joined: 08 Jun 2006
Posts: 18
Location: Aurora, IL.
Gas gauge reading on Instrument panel, 66 Fairlane

I know we have discussed this a couple times in the past, so maybe you guys know what things I should check first. My gas gauge is pegged at the "past full" mark. I've changed the fuel sending unit twice (purchased new sender units from Auto Krafters), and have purchased a totally new gas tank as the one I had, had a dent in it anyway.

I ran out of gas the other day (again), and the gauge still reads beyond full when I know that there is only a gallon or two in there. When I turn the car off the gauge goes down to empty. When I turn the car on, it goes past full.

Is my problem with the instrument panel? Thanks for all of your help.

Brent

PS: I had to re-regester as I haven't visited here since the format was changed, and I forgot what my old password was.

Any
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Brent


1966 Fairlane, 408 Stroker motor, 5 speed Tremec, completed project

Post Fri Jun 09, 2006 7:45 am 
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Rylic
Senior Member


Joined: 18 Mar 2006
Posts: 240
Location: Jackson, TN

Make sure you have a good ground at the sending unit. I know that was one cause of incorrect readings.

Post Fri Jun 09, 2006 8:09 am 
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fair67cp
Moderator


Joined: 08 Mar 2006
Posts: 189
Location: North West Maryland

Forgive me if this sounds stupid, but in changing the sending unit did you have to remove the float? All I can think of is maybe the float inside the tank is stuck. If you can replace the sending unit without checking this then that may be the problem. If replacing the sending unit means the part with the float has to come out and be checked, then this is a dumb post and I apologize accordingly! I just never had to deal with the mechanical fuel gauge assembly.
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MET

Post Fri Jun 09, 2006 8:42 am 
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Scott66gta
Senior Member


Joined: 09 Mar 2006
Posts: 284
Location: syracuse, NY
vr IN DASH

CHECK THE VOLTAGE REGULATOR IN THE DASH, AS WELL AS THE GROUND WIRE FROM THE BATTERY TO THE BODY hth

Post Fri Jun 09, 2006 3:47 pm 
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LiLMike
Member


Joined: 09 Mar 2006
Posts: 53
Location: Canton,Ohio

Sounds like a wiring problem. It could be a missing or lose ground. The sending unit must have a good ground. I have heard of some people fixing this by running a wire from the sending unit to the chassis. I had this problem many years ago and it was a pinched wire. I removed the tranmission and caught the sending unit wire that runs to the guage in the tranny cross member. I would check the grounding problem first.
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1966 500XL 390 C6 Mostly stock at the moment.

Post Sat Jun 10, 2006 5:19 am 
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Overdrive
Member


Joined: 09 Mar 2006
Posts: 63
Location: Colorado

On the Fairlane, battery power is routed through the voltage regulator, gauge and finally the tank unit. The tank unit is actually a variable resisto

When the tank is full, the float is up and the resistance is low. The gauge reads full.

When the tank is low, the float is down and the resistance is high. The gauge reads empty.

In your case, the gauge reads full regardless of the actual fuel level. Here are some things to look for
1. shorted wire between the gauge and the fuel tank
2. tank unit is stuck in the up position
3. defective gauge
4. If the temperature gauge also reads hot, the voltage regulator is probably defective.


Since the tank is empty, remove the fuel transmitter. Connect a bonding wire from the transmitter to the battery ground. Lift and lower the float while your helper observes the gauge. You can also disconnect the power wire and use an ohm meter to check the resistance of the transmitter while moving the float.

Checking for a short can be difficult. Try using a test wire from the negative side of the gauge directly to the fuel transmitter. Check as described above.

Post Sat Jun 10, 2006 10:18 am 
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berry32ford
Junior Member


Joined: 08 Jun 2006
Posts: 18
Location: Aurora, IL.
'66 fuel gauge reading...update

Thanks very much guys...all good ideas. If I can tell you what I've done in the past 24 hours, maybe that will narrow some things down for me. I should tell you that I installed an aftermarket wiring kit and I pretty much rewired the entire car, except for under the dash. New fuse panel also. Everything on the car work fine...except the gas tank level gauge.


I ran a new wire from the back of the level gauge to the sending unit, and there was no change. I also ran a ground wire from the sending unit to a good ground, and again, no change.

So, I took out the front seat, and went under the dash. The wiring there is still pretty much stock, but coming out of the back of the fuel level gauge there are 2 wires. One goes to the sending unit (black-green), and one goes to my fuse panel. (Yellow-White). My Constant Voltage Unit that is located under the dash is not connected to anything...there are no wires going to it. Should this be involved in the wiring of the gas sending unit somewhere??? If so, what should I do??? Should the Constant Voltage Unit be wired in between the fuel gauge level indicator and the sending unit? I have the shop manual, but I can't seem to find where the constant voltage unit is wired into anything else.
Thanks for your help guys
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Brent


1966 Fairlane, 408 Stroker motor, 5 speed Tremec, completed project

Post Sat Jun 10, 2006 1:16 pm 
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berry32ford
Junior Member


Joined: 08 Jun 2006
Posts: 18
Location: Aurora, IL.
'66 fuel gauge reading...update

Thanks very much guys...all good ideas. If I can tell you what I've done in the past 24 hours, maybe that will narrow some things down for me. I should tell you that I installed an aftermarket wiring kit and I pretty much rewired the entire car, except for under the dash. New fuse panel also. Everything on the car work fine...except the gas tank level gauge.


I ran a new wire from the back of the level gauge to the sending unit, and there was no change. I also ran a ground wire from the sending unit to a good ground, and again, no change.

So, I took out the front seat, and went under the dash. The wiring there is still pretty much stock, but coming out of the back of the fuel level gauge there are 2 wires. One goes to the sending unit (black-green), and one goes to my fuse panel. (Yellow-White). My Constant Voltage Unit that is located under the dash is not connected to anything...there are no wires going to it. Should this be involved in the wiring of the gas sending unit somewhere??? If so, what should I do??? Should the Constant Voltage Unit be wired in between the fuel gauge level indicator and the sending unit? I have the shop manual, but I can't seem to find where the constant voltage unit is wired into anything else.
Thanks for your help guys
_________________
Brent


1966 Fairlane, 408 Stroker motor, 5 speed Tremec, completed project

Post Sat Jun 10, 2006 1:16 pm 
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berry32ford
Junior Member


Joined: 08 Jun 2006
Posts: 18
Location: Aurora, IL.
'66 fuel gauge reading...update

Thanks very much guys...all good ideas. If I can tell you what I've done in the past 24 hours, maybe that will narrow some things down for me. I should tell you that I installed an aftermarket wiring kit and I pretty much rewired the entire car, except for under the dash. New fuse panel also. Everything on the car work fine...except the gas tank level gauge.


I ran a new wire from the back of the level gauge to the sending unit, and there was no change. I also ran a ground wire from the sending unit to a good ground, and again, no change.

So, I took out the front seat, and went under the dash. The wiring there is still pretty much stock, but coming out of the back of the fuel level gauge there are 2 wires. One goes to the sending unit (black-green), and one goes to my fuse panel. (Yellow-White). My Constant Voltage Unit that is located under the dash is not connected to anything...there are no wires going to it. Should this be involved in the wiring of the gas sending unit somewhere??? If so, what should I do??? Should the Constant Voltage Unit be wired in between the fuel gauge level indicator and the sending unit? I have the shop manual, but I can't seem to find where the constant voltage unit is wired into anything else.
Thanks for your help guys
_________________
Brent


1966 Fairlane, 408 Stroker motor, 5 speed Tremec, completed project

Post Sat Jun 10, 2006 1:17 pm 
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