Seems like my gas gauge is stuck on 1/2.  This happened once before and I ran out of gas.  I put some gas in the tank and blew air from the front to the rear of the gas line and then from the rear to the back and it cleared it up.  I hate to keep doing this, but it seems like whenever I try to fix something I know nothing about I mess up.  Should I go ahead and replace the sending unit or try something else.  All help will be appreciated.

Open the Cover on the Floor of he Trunk. Disconnect the Wire from the Gauge Sender. With the Ignition Key turned to Accessory so the Gauges are powered touch the Wire Terminal to ground. If The Gauge on the Dash moves to full try adding a good ground Wire from One of the Screws holding the Sender in the Tank.If the Dash Gauge continues to work Properly You may have fixed the Problem. If Dash Gauge does not work I would say U have a bad Sender in the Gas Tank and probably need to replace it. If the Dash Gauge does not move when the Wire is grounded the Dash Gauge is likely the Problem. Most of the Time its either a bad Ground for the Sender or bad Sending Unit. I don't know why blowing out the Fuel Line would fix the Problem with the Gauge. Maybe Someone else here would know why that would work temporarily. 

  

Possibly the float arm hangs up on something that prevents it from dropping with the fuel level. Blowing air through the lines may have dislodged it but now it's hung up again.I agree with OCM, do check the power and ground at the sender but while you're there pull the sender out and have a look-see. Best done with the tank empty or nearly so. One other thought: my '53 would "run out of gas" sometimes even with a full tank. Let it sit for a few minutes and it would fire up and behave as if nothing was amiss. Drove me bat shirt crazy. Turns out a PO had dropped the foil seal from a bottle of Sta-Bil in the tank. The seal would sometimes block the outlet to the fuel line. I drained the tank and got the seal out through the sender hole with a shop vac.

Using a shop vac to vacuum anything out of a gas tank can be dangerous!  Even if the tank is empty the tank contains fumes that will enter the shop vac - possibly somewhere in the 14:1 air fuel ratio. Sparks in the shop vac motor do occur.

If your 56 still has the original King Seely fuel gauge sender, I would be reluctant to replace it. These units are hard to find and if you can find one they usually sell for around $300. The King Seely operates on opening and closing contact points which send electrical pulses,which vary with the float level, to the gauge. The only after marketsenders I have seen send a steady electrical power, the amount which varies with the float level, to the gauge. The original gauge was not designed to work this way and while they will show a movement of the gauge needle, they are not at all accurate (Do a search on this forum and also the Ford Barn forum for many complaints on the aftermarket senders). It might be possible to fix your original sender if it is at fault. Carefully pop the cap off with a screwdriver and clean the clip where it makes contact with the inside of the cap when it's installed. Also clean the inside of the cap where it makes contact with the clip. While the cap is off, check the points. If you clean them, the sender might start working again.Finally, check the thin induction wire that wraps around the bi-metalic point arm. If it's broken, an auto electrical shop might be able to repair it. The first thing to do is make sure the sender is well grounded, as already suggested. If it were me, I would run a ground wire from one of the sender to tank mounting screws and connect the other end to the frame of the car. Scrape the frame so you see shinny metal where you attach the wire.

To test the gauge, hook up two 1.5 volt flashlight batteries with the two wires long enough to reach up under the dash to the two terminals on the back of the gauge. It doesn't matter which wire goes to which terminal. The steady 3 volts should cause the gauge to register ½tank.

Thanks for posting that Info. Very useful to know how to try and repair. these. I know there are a couple of Companies that will repair these original Units. Google Search should show them.

  

One item of correction: The wire wrapped around the bi-metal is not for "induction"; it heats the temperature-sensitive bi-metal element to change it's "springiness", thus changing the average current flowing through the sensor and gauge (which is also "heat-sensitive" and moves the indicator needle. Very similar operation for the heat gauge.

Hope this helps.

Regards, JLB

55 Ford Crown Victoria Steel Top

bergmanj - you are correct and I misspoke. I should have said "resistance wire". The resistance wire is wrapped around the bi-metal point arm which heats it when the points are closed. Since the two metals of which the point beam is made have different coefficients of expansion, one lengthens more than the other - causing the beam to bend and the points to open. When the beam cools, the points close again and the cycle is repeated.   Thanks.

Sounds like the float is hanging up.   Remove the sending unit and observe how the arm and float are moving.


54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ