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Terry,OH · 07-21-2011, 02:55 PM

The hydrostatic sending unit, in the tank can create a small amount of air pressure. The pressure is sent to the dash unit through the small tube. Once the pressure is in the back of the gas gauge it displaces a special red liquid to the glass tube in the front of the gauge, you just read the height of the red liquid in the glass tube and you have the fuel level in the tank. The small tube is available through several of the aftermarket suppliers in brass tube and works well. The fittings on the two ends of the small line are soldered on to the tube, and the connections have to be air tight. There is no need to tighten any of the connections too hard. Many times the dash gas gauge will not work. As mentioned the rear hex shaped tube on the rear of the gauge is the tank to store the red liquid. there is a very small tube between the hex tank and the glass tube and the small tube can become blocked with dried up liquid and needs to be open to allow the fluid to move back and forth between the hex tank and the glass tube. Yes one of the larger tubes in the sending unit is a air vent for the gas tank, it should be open if not several bad things could happen, such as, a vacuum developing in the tank preventing the fuel pump from working.

07-21-2011, 02:55 PM	#2
Terry,OH Senior Member Join Date: May 2010 Posts: 5,395	Re: '32 Gas gauge ???s The hydrostatic sending unit, in the tank can create a small amount of air pressure. The pressure is sent to the dash unit through the small tube. Once the pressure is in the back of the gas gauge it displaces a special red liquid to the glass tube in the front of the gauge, you just read the height of the red liquid in the glass tube and you have the fuel level in the tank. The small tube is available through several of the aftermarket suppliers in brass tube and works well. The fittings on the two ends of the small line are soldered on to the tube, and the connections have to be air tight. There is no need to tighten any of the connections too hard. Many times the dash gas gauge will not work. As mentioned the rear hex shaped tube on the rear of the gauge is the tank to store the red liquid. there is a very small tube between the hex tank and the glass tube and the small tube can become blocked with dried up liquid and needs to be open to allow the fluid to move back and forth between the hex tank and the glass tube. Yes one of the larger tubes in the sending unit is a air vent for the gas tank, it should be open if not several bad things could happen, such as, a vacuum developing in the tank preventing the fuel pump from working.