SpudFiles

This valve no longer closes when I introduce air.
What is the appropriate way to troubleshoot this?

What are you using as a air source? There is a topic on trouble shooting valves in the "How To" section.

Welcome to Spudfiles!

I use an air compressor.

Solenoid valves need air to be introduced rather quickly in order to seal, how are you filling your chamber?

I just noticed your valve is still stock/un-modded. Follow this guide: http://www.spudfiles.com/how-to-database/topic305.html and it should solve your valve issue.

There's a real downside to purchasing a gun such as this one. Complete ignorance about what I really have. What is the black trigger screwed into the valve doing now? Is the idea I need to replace the black trigger with a blow gun? Or do I need to take the valve apart and try greasing the diaphragm?

What is the black trigger exactly?

Does air leak from the barrel or the trigger when you're trying to fill?

Take the valve apart and if it has a small metal rod going through the diaphragm remove it, replace the black thing that looks like the male half of a quick disconnect and put a blow gun on there. The blow gun will fire the cannon. Did you read the guide I linked you to?

The air is coming out of the barrel. When I put the compressor on to add air, it ejects the potato. I'm really not sure what the black trigger is doing or failing to do. I'm guessing it got out of wack somehow.

I did look at the mod link. It is a hair confusing, because the pictures and instructions got scrambled when the forum was ported. I'm drinking from a firehouse, trying to get enough understanding not to do something rash. But I'm going to a big wedding in a week, and the gun is supposed to be a big part of the hi jinks. Must fix it this weekend.

I think I'm getting the picture now. I assume the purpose of the black trigger I am to replace with the blow gun is to let pressure off the valve, which causes it to fire. I am making two fixes, replacing the trigger and taking the guide rod out of the valve because one of those moves will probably fix whatever the problem is and the other will increase reliability (or will it increase muzzle velocity?).

Thank you for your help!

Essentially your valve has already been modded for pneumatic actuation, did you purchase the cannon as-is? If so, out of interest, where from?

Replacing the valve with a blowgun probably won't increase performance too much.

There might be some debris which is preventing the diaphragm from seating properly, I suggest opening the valve, removing the diaphragm and making sure it and the ring it seals agains are clean and free of dirt and debris.

I think I got this gun from SpudTech.com.

I opened the valve and found this held into the valve by a spring. Not what I expected. It was dry and tightly sealed to the valve. Clean as a whistle. 'Sup with this?