Pop-off valve opens on start

I've got a portable, belt-drive compressor (Coleman/Sanborn) that works fine except the pop-off valve opens when the compressor starts up (auto start, switch is factory set for 100 psi and the gauges confirm that's when it comes on). I've replaced the pop-off valve, but it still does it. Pop-off is 145 psi fixed. When set pressure is reached (130 psi), the pop-off valve does not open.

When the valve opens, it stays open for maybe 5-10 seconds, then closes on its own. At that point the pressure builds up normally and the pressure switch shuts the motor off at 130 psi.

I'm guessing there is a pressure pulse when the compressor starts up. This is a fairly cheap compressor with a cast aluminum manifold with an integral regulator. The pop-off valve is close to the connection from the compressor itself to the manifold. I was thinking of adding a tee in between the manifold and the pop-off valve, and putting maybe 6" of pipe on it (with a cap, of course) to provide some volume for the pulse to expand into.

So first, does my diagnosis sound reasonable, and second, is a little expansion volume likely to help? I really don't want to increase the pop-off valve set pressure and having the silly thing open when the compressor starts is pretty startling.

Thanks
Bob Jones

____________________
Bill says...

Bob, if by "pop off valve" you mean PRV, that it opens briefly on start up suggests to me that you may have debris build up in the check valve into the tank.

I can think of no other reason why the PRV should act as yours does except, of course, that it needs replacing.

Cheers,

Bill