After sitting all winter, my gaffrig air actuated mufflers won't stay closed. When activating them, the pump closes them just fine, but they open back up after about 5 seconds. I assume there is a bad valve or something that is letting the air escape. I can't find anywhere the air is leaking upon initial inspection. There appears to be some type of solenoid attached to the pump. Not sure if that may be the problem and it is allowing the air to leak back.
Last year they used to stay completely closed for about 15 mins before reactivating them.

Ideas????????

Yes...take them off

When we were kids we used soapy water to find the leaks in our bike tires.

Ok, I'm leaving now

The solenoid dumps the air out of the lines after the pump shuts off, allowing the cylinders to retract. You could have a leak there, in a line or a piston seal in a cylinder. Or the pump could be worn out and not supplying sufficient air.

If you have the room, you can hook up a pump to a 1/2 gallon tank and run a pressure demand switch. Then the pump only runs when the tank needs to be refreshed. The pump will last much longer doing that- those pumps only had short duty cycles- like 20%.

Just went through this myself after having the motors out. Snug up all hose fittings and I bet you'll fix the prob.

I like the idea of adding a pressure demand switch and a small reserve tank. I may have to look into that.

Good call
Just snugged up the hose connections at the mufflers and all is good.

You can find all the stuff either on Ebay (the exact same stuff is used on those low-rider air suspension cars) or from Grainger.