On 9/23/16 8:51 AM, Mike Marlow wrote:



Or it could be something as simple as a blocked vent hole.


The OP states that the vent is open. I'd be more suspicious of a
blocked pickup tube. His test of turning it upside down is not really a
very good test for this condition. I'd take the pickup tube right off,
and run a cleaning brush through it with solvents. At the same time,
inspect the head of the gun where the tube attaches. It only takes a
little bit of clog to mess these things up.



Yep, siphon guns usually work with a venturi at the top of the pickup
tube. If anything from this point forward is gunked up, the air will
start to bypass the spray head and turn down the pickup.

-BR