Air in primer pump bowl

[Rawze]

Just some random guessing...

Davco or other fuel filter seals allowed to suck air?.

.. or maybe a bad fitting on the suction side lines?.

.. Or maybe cracked pick-up tube in the fuel tank?.


Sometimes someone has to resort to extreme measures to find suction side leaks when all other options have been exhausted, and no one can find it ....

-- Blocking off the one side bleeder hose .. and using the other bleeder circuit to pressurize the fuel tanks up to to 5 psi, regulated air pressure (BUT NO HIGHER), and letting it sit for a couple-three hours + wiggling lines around gently at their fittings to see if a pickup line drips, is one way to find suction side hose or filter housing leaks.

CAUTION !!!!!!!! .. NEVER, EVER, EVER, REMOVE THE FUEL TANK FILL CAPS WHILE THE TANKS ARE UNDER ANY KIND OF POSITIVE PRESSURE!!!>. It only takes about 1 or 2 psi pressure for there to be enough force built up behind them to break your wrist or put someone in the hospital for attempting to unscrew them. The pressure at the cap is amplified greatly by the volume of the tank itself.

After / Aside from leak testing the suction side piping and filters ...

-- Pressurizing the tanks like this and having the fuel line(s) going into the bottom of a bucket to see if there is air getting in them is also how to check if you have cracked pick-up tube(s) in a tank as well. A cracked pick-up tube at the top of a fuel tank can be otherwise difficult to find.