Author Topic: fuel guage issue  (Read 262 times)

Offline joewhitmire

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  • Name: J Whitmire
fuel guage issue
« on: November 07, 2017, 10:17:42 PM »
Hello all, I have a 56 Fleetwood sixty special, and my fuel guage will only read 1/2 full even though it is full. Any help on how to resolve this would be greatly appreciated. I just had the tank blasted and coated and also installed a new sending unit. Thought that might fix my problem, but it didnt.

Online carguyblack

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  • Name: Chuck Dykstra
Re: fuel guage issue
« Reply #1 on: November 08, 2017, 06:01:53 AM »
When I replaced my sending unit, I tested it outside the tank with alligator clips and manually operated the float rheostat to make sure the needle on the gauge had full movement. I'd suggest trying that before digging into your dash by blaming the fuel gauge itself. Sound like you have good ground and power to the sending unit but you may have a defective unit.
Chuck Dykstra

Offline J. Gomez

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Re: fuel guage issue
« Reply #2 on: November 08, 2017, 07:18:18 AM »
Your symptoms indicates you may have an open ground at the case of the gauge or a bad coil.

Try to remove the “brown” wire at either the gas tank or the gauge, depending on which side you hate the most, they are both a pain.   :(

Turn the ignition to “on” and see if the gauge pegs to full, if it just goes to the same area ˝ that will tell you the problem is at the gauge.

There are two coils at the gauge on goes to the +12V and the other goes to ground, the fuel sender connects between the two coils. The resistance from the fuel sender will add more or less ground resistance between the coils so one will pulls the gauge to “E” while the other pulls the gauge to “F”.

If the ground at the coil is open the gauge would only go from “E” to ˝ even if the fuel sender is in the full position.

HTH

Good luck..!
J. Gomez
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Time is irrelevant when you work on your classic car, eventually you will enjoy it..!

Offline joewhitmire

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  • Name: J Whitmire
Re: fuel guage issue
« Reply #3 on: November 08, 2017, 03:10:42 PM »
Thanks for all of your comments. Funny thing is, I have done all of the testing per the manual and when I remove the wire from the sending unit at the tank, turn switch on and it pegs to past ful and this what it is supposed to do. This tells me the wire is good and supposedly the guage is good as well. It is a new sending unit I got from McVey's. I assume its good, so i go fill the car up last night and now, the guage will read 1/2 full when the tank is totally full. I'm stumped

Offline J. Gomez

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Re: fuel guage issue
« Reply #4 on: November 08, 2017, 04:03:07 PM »
Thanks for all of your comments. Funny thing is, I have done all of the testing per the manual and when I remove the wire from the sending unit at the tank, turn switch on and it pegs to past ful and this what it is supposed to do. This tells me the wire is good and supposedly the guage is good as well. It is a new sending unit I got from McVey's. I assume its good, so i go fill the car up last night and now, the guage will read 1/2 full when the tank is totally full. I'm stumped

Joe,

Hmm well that was the missing piece from your original post.   ;)

Since you have already done all of the testing there is one small detail you can try, although it may not be the cause but it sure is it easier before you tackle the next one by removing the sender.

Connected a wire from a good chassis/frame source to the fuel sending unit at the tank and see if that solves the problem. The tank relies on the metal fuel line for the ground source and it is not a reliable one.

If that fails them as my good friend Chuck mention above the sender is the issue.   :(

Good luck..!
J. Gomez
CLC #23082

Time is irrelevant when you work on your classic car, eventually you will enjoy it..!

Offline Jeff Rose CLC #28373

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Re: fuel guage issue
« Reply #5 on: November 08, 2017, 04:04:44 PM »
Don't go to that extent yet. Touch a wire from a good ground to the tank, and if possible the sending unit screw itself. This is a quick check before you start pulling things apart. It is possible that with the new paint on the tank, etc that you may have a weak ground.
Jeff
Jeff
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1970 Coupe DeVille
1955 Series 62

Offline Jeff Rose CLC #28373

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Re: fuel guage issue
« Reply #6 on: November 08, 2017, 04:07:00 PM »
J Gomez- we posted the same thing at the same time.
Jeff
Jeff
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1970 Coupe DeVille
1955 Series 62

Offline J. Gomez

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Re: fuel guage issue
« Reply #7 on: November 08, 2017, 04:24:03 PM »
J. Gomez
CLC #23082

Time is irrelevant when you work on your classic car, eventually you will enjoy it..!

Online carguyblack

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  • Name: Chuck Dykstra
Re: fuel guage issue
« Reply #8 on: November 08, 2017, 05:22:03 PM »
I remember on an old sending unit that the contact was being made early in the arm drop but as the float would go up, the contact along the windings just wasn't being made indicated by the fuel gauge only going so far.
Neither the sending unit removal nor the fuel gauge itself are fun removals, but for me, the sending unit was easier. Now that I said that, I wonder with some contortion, if you could remove the gauge from the cluster from underneath the dash rather than removing the whole thing?
That instrument cluster removal is simply a full-blown pain.
Chuck Dykstra

Re: fuel guage issue
« Reply #9 on: November 08, 2017, 06:16:52 PM »
It sounds like the sender arm is bent at the wrong angle such that with the tank full, the arm is only swinging the contact on the rheostat halfway up the rheostat.  I ran into this very thing once and had to fix it by bending the arm.  I think the way I did it was to get the tank to some known fill level (1/4, or 1/2 or full) and then note how the gauge is reading and through iteration bend the arm a little at a time and note the new reading on the gauge.  Lather, rinse, repeat. Tedious, but it worked.
Art Gardner


1955 S60 Fleetwood sedan

Offline The Tassie Devil(le)

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Re: fuel guage issue
« Reply #10 on: November 08, 2017, 08:03:53 PM »
Don't forget that a new sender unit might have an arm that isn't swinging in the same arc of rotation as the original, and the float could be binding on the side of a baffle.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
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Offline TonyZappone #2624

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Re: fuel guage issue
« Reply #11 on: November 09, 2017, 05:09:17 AM »
After many futile (and costly) attempts to repair fuel gauges in 50's Cadillacs, I kinda gave up.  Fill tank, set trip meter to 0.  When you get to 75 miles, fill tank again.
Tony Zappone, #2624
1936 Pierce-Arrow conv sed
1947 Cadillac Conv cpe
1958 Cadillac conv cpe
2002 Thunderbird
2002 Cadillac DTS
2016 Cadillac CT6 Platinum

Offline Jeff Rose CLC #28373

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  • Name: Jeff Rose
Re: fuel guage issue
« Reply #12 on: November 09, 2017, 11:27:32 AM »
Fill tank, set trip meter to 0.  When you get to 75 miles, fill tank again,
That's exactly what I do. Except the 70 has those cheesy plastic reset knobs that crack so I just take a picture of the odometer every time I fill it...... and I live dangerously-I go 100 miles!
Jeff
Jeff
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1970 Coupe DeVille
1955 Series 62

Offline TonyZappone #2624

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Re: fuel guage issue
« Reply #13 on: November 09, 2017, 12:06:50 PM »
A picture!  Modern technology.  God Bless
Tony Zappone, #2624
1936 Pierce-Arrow conv sed
1947 Cadillac Conv cpe
1958 Cadillac conv cpe
2002 Thunderbird
2002 Cadillac DTS
2016 Cadillac CT6 Platinum

Offline J. Gomez

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Re: fuel guage issue
« Reply #14 on: November 09, 2017, 12:38:14 PM »
Well that is one way of handling a non-functioning fuel gauge  ;D  it also helps with one getting sea sick by looking at gauge fluctuating when the tank is ˝ empty and fuel sloshing all over.   ;)
J. Gomez
CLC #23082

Time is irrelevant when you work on your classic car, eventually you will enjoy it..!

Offline bcroe

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fuel guage issue
« Reply #15 on: November 09, 2017, 03:01:56 PM »
Quote from: TonyZappone #2624
After many futile (and costly) attempts to repair fuel gauges in 50's Cadillacs, I kinda gave up.  Fill tank, set trip meter to 0.  When you get to 75 miles, fill tank again.

Those gauges can be fixed, if you diagnose the issue. Worst case put in a
standardized pickup unit, and use one of those "match anything to anything'
electric boxes. 

My cruiser will do 350-400 miles before needing a fill.  Bruce Roe