Mallory 4309 fuel pres. regulator is inconsistent

[bill dedman]

Anybody got any experience with this regulator? I set it on 6psi and it runs there for awhile and I look again and it's down to 2psi.

Look again a few minutes later, and it's back up to 6...

It has the boost reference tube connected to NOTHING right now. Pump is a 60psi Walbro 392 and both the supply tubing and the return are 3/8."

Fuel cell is half full of gasoline; The return dumps in on one side of the top (5 gallon fuel cell) and the supply line is on the other side. No rubber foam in the fuet cell, just a big, hollow cube.

The plunger in the regulator appears to be hanging up and allowing too much fuel to return to the tank (cell.) The regulator has about 10 minutes running time on it (virtually brand new.)

Is there any significance to the strength of that spring on the inside of the regulator?

Anybody else ever had a problem like this?

I'm stumped...