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  #1  
Old 08-13-2014, 06:30 PM
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Fuel gauge reading tank as full.

Hey guys. Filled up my truck before a fairly long drive back home after visiting family. On the trip down, the fuel gauge worked as it should and used a little over a 1/4 tank. For the trip home, I filled it again, but the fuel level did not drop on the drive home. It's still reading full, but I know that's impossible. I haven't checked the ground or anything yet, just thought maybe one of you would have an idea why it's still reading full . I'm wondering if maybe the sending unit is fried. Thanks guys!
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Old 08-13-2014, 08:23 PM
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Float arm could be stuck (less likely), rheostat in the sending unit is shorted, or a short to ground somewhere between the sending unit and gauge. Pull the sending unit lead and see what happens.

I assume the temperature gauge does not peg toward H?
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Old 08-13-2014, 08:25 PM
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You'll have to troubleshoot it to find out why.
Unplug the sending unit and turn the ignition to "on". Does the gauge stay on "E" or does it still swing over to full? If it goes to full then either there's a problem in the wiring or the gauge is bad. If it now stays on "E" then probably a bad sending unit.
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Old 08-14-2014, 02:33 AM
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Quote:
Originally Posted by fmc400 View Post
Float arm could be stuck (less likely), rheostat in the sending unit is shorted, or a short to ground somewhere between the sending unit and gauge. Pull the sending unit lead and see what happens.

I assume the temperature gauge does not peg toward H?
The temp. gauge seems to be working fine. I'll do some messing around with it tomorrow and see what happens. Just odd that it happened so suddenly. Thanks for the reply.
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Old 08-16-2014, 09:47 PM
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Quote:
Originally Posted by mikeo0o0o0 View Post
You'll have to troubleshoot it to find out why.
Unplug the sending unit and turn the ignition to "on". Does the gauge stay on "E" or does it still swing over to full? If it goes to full then either there's a problem in the wiring or the gauge is bad. If it now stays on "E" then probably a bad sending unit.
I unplugged the sending unit. It now stays on E. I picked up a sending unit at the pull and pay. When I have some time, I will put that one in and see what happens. Thanks guys for the suggestions.

What's the best way to test the sending unit I picked up, and also to test the one that's already in there to see if it is indeed bad?
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Old 08-16-2014, 09:59 PM
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Use an ohm meter to check the resistance. I can't remember the value off the top of my head, I'll have to look them up.
Hook the meter's leads to the terminals of the sending unit. Move the float arm, the needle should move with the arm.
Do the same to the bad unit, chances are, the needle won't move when you move the float arm.

EDIT: 8-12 ohms full and 70-73 ohms empty.
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Old 08-16-2014, 10:35 PM
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My input is usually wrong, but mine did the same thing today while offroading. I went up a few more hills, hit a few more mud bogs and apparently unstuck it. Works fine
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Old 08-16-2014, 11:50 PM
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Quote:
Originally Posted by mikeo0o0o0 View Post
Use an ohm meter to check the resistance. I can't remember the value off the top of my head, I'll have to look them up.
Hook the meter's leads to the terminals of the sending unit. Move the float arm, the needle should move with the arm.
Do the same to the bad unit, chances are, the needle won't move when you move the float arm.

EDIT: 8-12 ohms full and 70-73 ohms empty.
On the pull and pay sending unit, the ohms are within tolerance. I'll have to lift my bed a little bit to get at my old one. Is there a way to replace just the rheostat, or is it easier to do as a complete unit? Also, I want to put a new filter screen on, but not sure how to get the old one off. Don't want to damage it. Thanks.
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Old 08-17-2014, 03:01 AM
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Drop the tank or lift the bed, dropping the tank is easier IMO. Bed bolts are usually really rusty and during the removal process the you will mess up the square lock flange in the bed.

The rheostat, arm float and pick up tube are all one.

The filter sock is bonded to the end of the pick up tube with some kind of material that is fuel resistant.
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78 (79 headlights) 460 4 spd, 4", a/c and 35's
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99 Ranger 4x4, 98 Expedition 4x4, 73 Bronco Hillbilly-Bug
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Old 08-17-2014, 03:38 AM
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Quote:
Originally Posted by 77&79F250 View Post
Drop the tank or lift the bed, dropping the tank is easier IMO. Bed bolts are usually really rusty and during the removal process the you will mess up the square lock flange in the bed.

The rheostat, arm float and pick up tube are all one.

The filter sock is bonded to the end of the pick up tube with some kind of material that is fuel resistant.
So I can just get the filter sock off as well as I can I guess. That's what I thought on the rheostat. I have had the bed off before, and the first time I took the bolts off, they were really rusty. But I cleaned them up and put anti-seize on the bolts, so for now, I think it would be easier to lift the bed up. I still have to over to MO to see this field of Ford dreams you go to.
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Old 08-17-2014, 03:50 AM
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Getting the old filter off is not the problem, finding what ever Ford used to bond it to the pick up tube is the hard part. Maybe mikeo0o0o0 knows?

Was a used one the much cheaper than a new one?

Since your bed has been off before that's the easier route to go.

What "Ford field of dreams" are you talking about?
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77 351M auto, a/c, add a leaf 33x12.50's
78 (79 headlights) 460 4 spd, 4", a/c and 35's
79 351M 4spd 6" Skyjacker Edelbrock-Holley-Hedman 35's
99 Ranger 4x4, 98 Expedition 4x4, 73 Bronco Hillbilly-Bug
71 Bronco 302 35" Boggers 5.58 gears spool/locker
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Old 08-17-2014, 06:05 AM
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[quote=77&79F250;14589410]Getting the old filter off is not the problem, finding what ever Ford used to bond it to the pick up tube is the hard part. Maybe mikeo0o0o0 knows?

Was a used one the much cheaper than a new one?

Since your bed has been off before that's the easier route to go.

What "Ford field of dreams" are you talking about? [/quote

It would be good to know what they used for an adhesive. The filters are available, so there must be something they suggest to use to adhere them.

Yeah, a used sending unit was 6 dollars at the pull and pay.

The one you photographed 50 or 60 trucks at.
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Old 08-17-2014, 08:19 AM
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Quote:
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finding what ever Ford used to bond it to the pick up tube is the hard part. Maybe mikeo0o0o0 knows?
I went through the parts catalog and two different shop manuals ('73 & '77)
There's no mention of the pickup mounted filter sock in either of them, let alone how to change it.
I also went through Ford's list of chemicals and again, nothing.
This is one of those items that Ford fails on when you're looking for info.
I did a search online and you might try something like this:
Robot Check Robot Check
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Old 08-18-2014, 02:38 PM
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Quote:
Originally Posted by fmc400 View Post
Float arm could be stuck (less likely), rheostat in the sending unit is shorted, or a short to ground somewhere between the sending unit and gauge. Pull the sending unit lead and see what happens.

I assume the temperature gauge does not peg toward H?
I do believe you were correct about the float arm being stuck. I went for a drive yesterday hit a couple of bumps and all of a sudden the gauge went down to the half mark, which is about right. I think I'll still take the bed off at some point and look at the sending unit and see if I can clean it up a little bit, and look to see if there's a bunch of junk in the tank too. So for now, problem seems to be solved. Thanks for everyone's help!
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Old 08-18-2014, 03:33 PM
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Tie a small piece on rope on one end of a piece new or rust free 2 or 3 ft HD log chain and roll and shake the tank around, the chain will loosen the scale and rust.

Inside tank treatment kits available. New metal tank all as much, get plastic no rust ever again. MTS COMPANY, L.C. - Ford Pickup fuel tanks

I am sure pulling and cleaning the sending unit and giving it the once over will help.
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77 351M auto, a/c, add a leaf 33x12.50's
78 (79 headlights) 460 4 spd, 4", a/c and 35's
79 351M 4spd 6" Skyjacker Edelbrock-Holley-Hedman 35's
99 Ranger 4x4, 98 Expedition 4x4, 73 Bronco Hillbilly-Bug
71 Bronco 302 35" Boggers 5.58 gears spool/locker
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Old 08-18-2014, 03:33 PM
 
 
 
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