air entering sight glass on fuel pump

[relick]

I needsome help from the brains trust!! My power major has bubbles coming into the glass on top of the fuel pump, the bubbles are coming from the inlet pipe (or more accurately from the rectangular opening on the tank side of the glass)
I am also getting bubbles in the fuel tank. Of course the air entering the system stops the motor.
Would i be correct in suspecting the pump. I just dont see how the the bubbles are also coming back into the tank.................

[brockwood]

i had the same once had a pin hole in the pipe out of the tank

[Pavel]

I would suspect that you have a dodgy inlet poppet valve in the pump body which is allowing some fuel to be pulsed back to the tank. Can be caused by a weak spring not closing it off or dirt trapped on the disc.
You could check this out by turning the fuel off at the tank tap and unscrewing the pipe from the tank. Connect a rubber, or plastic hose to it and immerse the end into a small can of fuel. Using the priming lever to pump fuel should show if the above suspicion is correct.

Pavel.

[Brian]

An "of the wall" thought, how much fuel do you have in the tank? What tractor do you have?

The early Majors have a two position fuel tap in the tank, usually the fuel is drawn through a short standpipe in the fuel tap with a lower drilling in the base of the tap which is opened when the tap is fully open. If your fuel level was close too or below the level of the standpipe and crud was blocking the lower hole she may pull in air through the standpipe.

Blockage in the fuel tap in the tank can cause air to enter the lift pump bowl, I have had this quite a few times when the tap screen blocks. Filling from cans is not the best no matter how much care you take.

[Dandy Dave]

I had the same problem with my Power Major. Like Brian says, It was a blocked tank valve. Drove me nuts as it was a piece of a leaf that would sometimes get sucked down, and other times float around. Dandy Dave!