Gas gage not working
Lead Driver
Joined: Jul 2011
Posts: 6,599
Likes: 34
From: Rockingham, VA
Yes, there's a procedure in the Shop Manual. But to test the gauge and/or the sending unit, it tells you to use a new gauge. Well duh... 
This is how I determined my gauge is good and I needed a new sending unit. This works if you know the wire is good between the sending unit and the gauge.
With the key turned on, short the wire from the sending unit to ground. The gauge needle should start to move toward Full. If it moves, the sending unit is bad (assuming the tank has gas in it). If it doesn't move, the gauge is bad or the wire from the gauge to the sending unit is open.
Warning: Once the needle moves, the test is over. Don't leave the short on longer, or you might peg your needle.
This is how I determined my gauge is good and I needed a new sending unit. This works if you know the wire is good between the sending unit and the gauge.
With the key turned on, short the wire from the sending unit to ground. The gauge needle should start to move toward Full. If it moves, the sending unit is bad (assuming the tank has gas in it). If it doesn't move, the gauge is bad or the wire from the gauge to the sending unit is open.
Warning: Once the needle moves, the test is over. Don't leave the short on longer, or you might peg your needle.
Senior User
Joined: Feb 2011
Posts: 298
Likes: 1
From: Huntsville, Al
Here's a simple diagram for building a test unit to test the gauge.As for testing the sending unit , that can be done with a simple volt/ohm meter.
Laughing Gas
Joined: Nov 2006
Posts: 1,125
Likes: 4
From: Olive Branch,Ms
I been working on getting all my dash instruments working this past week. The fuel level sender is based upon resistance. My is rated 33 ohms to 240 ohms. On my with the arm all the way down it reads 33 ohms while with the arm all the way up is 240 ohms.With the sender out of the gas tank and wiring disconnected you can use a ohm meter to check the accuracy. My is a VDO brand v-226-007. If you us the number on the sender unit you can look up on the net the ohm rating. VDO V-226-001 is 10 to 180 ohms while V-226-008 is 0 to 90 ohms.
Parts Nerd Extraordinaire
Joined: Sep 2010
Posts: 4,372
Likes: 1,787
From: Western NY
This thead over here has some information about gas gauges and sending units and such that is a very interesting read:
https://www.ford-trucks.com/forums/1...correctly.html
https://www.ford-trucks.com/forums/1...correctly.html
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