Holley 390 carb help needed

[gtbrain]

I have a holley 390 carb on my 66 250.

If I let my truck sit for a couple of days without starting it, the accel pump on the carb will not send fuel to the squirters.

For some reason it builds up enough pressure to not allow linkage to work the lever on the pump.

If I pull the carb and loosen the 4 screws on the accel pump housing, it will shoot out fuel under pressure. I can then get the linkage to work the pump.

I am baffled. Anyone have a cure for this?