Fuel Gauge not working
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Junior User
Joined: May 2002
Posts: 77
Likes: 0
From: Oceanside USA
Fuel Gauge not working
I have a 70 F250 Camper Special w/ dual tanks. Neither of the tanks register fuel on the gauge. I have checked the gauge when I had the instrument cluster out, it worked when I applied 9vdc from a battery. I also checked the sending unit in the cab tank and it ohms at 68 empty and 10 full, I assume this is ok. I also have continuity on the orange and black wire from the S/U to the tank selector switch and switch seems ok. This where I left off, not sure what to check next and I do not have a schematic. Any suggestions?
Posting Guru
Joined: Feb 2002
Posts: 1,115
Likes: 1
From: seattle us
Fuel Gauge not working
I don't know what the resistance readings should be either, however I was having the same problem. Turned out the floats were bad and could never "float" to the top when full. It got saturated with fuel or something.
New User
Joined: Jan 2008
Posts: 0
Likes: 24
Fuel Gauge not working
Look for one of Steve83's posts .he has replied with the resistance values before.
Try searching all open forums with Steve83 as the author and *fuel sending unit* as the message not the title.
Try searching all open forums with Steve83 as the author and *fuel sending unit* as the message not the title.
Cross-Country
Joined: Feb 2003
Posts: 62
Likes: 0
From: Washington State
Fuel Gauge not working
I have sort of the same problem -- my tanks reads 1/4 when it's full and negative 1/4 when it's runnin' on E. I always carry extra gas -- not the perfect solution but it gets me by.
Mountain Pass
Joined: Apr 2002
Posts: 230
Likes: 0
Fuel Gauge not working
I have the exact same problem on my 71 F-100. The best I get is 60-75% on the fuel gauge on either tank when full.
I even went as far as to breadboard up a voltage regulator so that I could tune in a source voltage level for the guages that would make the fuel gauge show up full when the sender was fully up as opposed to the instrument voltage regulator .
But that screwed up the other guages, so I just kind of live with it. My take on it is that the switch and the extra connections necessary to multiplex the guage between the two tanks might be adding a couple of ohms to the circuit regardless of what tank it is. A couple of ohms is easy to accrue with old wiring, but when the minimum sending unit resistance is 10 ohms, that's a 20% error!.
Someday, I might get around to checking all the connections and the switch, but for now, I drive motorcycle style: I just keep a few gallons in the aux tank and drive on the main till I run out, and the aux gets me to the next gas station.
What I will try is bypassing the fuel gauge switch. Let us know if you try that.
I even went as far as to breadboard up a voltage regulator so that I could tune in a source voltage level for the guages that would make the fuel gauge show up full when the sender was fully up as opposed to the instrument voltage regulator .
But that screwed up the other guages, so I just kind of live with it. My take on it is that the switch and the extra connections necessary to multiplex the guage between the two tanks might be adding a couple of ohms to the circuit regardless of what tank it is. A couple of ohms is easy to accrue with old wiring, but when the minimum sending unit resistance is 10 ohms, that's a 20% error!.
Someday, I might get around to checking all the connections and the switch, but for now, I drive motorcycle style: I just keep a few gallons in the aux tank and drive on the main till I run out, and the aux gets me to the next gas station.
What I will try is bypassing the fuel gauge switch. Let us know if you try that.
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Senior User
Joined: Nov 2000
Posts: 366
Likes: 0
From: Calgary
Fuel Gauge not working
Not sure if this is the problem, but, my problem was inside the terminal connection. There's a small arm inside that slides up and down the terminals that broke off. Probably from somebody siphoning gas out and caught the hose on the float. Guess it could happen to both tanks.
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