Rivet Gun Help Needed - Always On

I recently purchased a 15 year old rivet gun that the previous owner never used. He had plans to build a Thorp, but never got started. The rivet gun looks brand new. I didn’t try it before I purchased it as the owner didn’t have a compressor any more.

A few weeks later I had a need for it and tried to test it out. Initially it didn’t run at all. I added some air tool oil and gave it a day or so and now it runs great, it just doesn’t turn off. There is some sort of leak past the trigger mechanism so if I hook up the air hose it is always on.

It is a US Industrial Tool model E3. I’m including a parts list that came with it. I’ve called US Industrial for some help and the tech support guy had never seen one before and his first suggestion was to buy a newer tool.

I’ve disassembled the handle and trigger assembly. Below are some pictures. In my mind the issue must be a leak past items 6 and 7. The metering valve (#10) is after the trigger so after the leak. I’ve made sure everything is clean and replaced the o-ring that is part of #6.

I’ll probably order replacement #’s 6 & 7. Unfortunately they are $30 each. It is disappointing that I didn’t get much help from the manufacturer.

Does anyone know something else that I could try? I’m about to give up on this.
Thanks,
Doug

I'd look closely at all the o-rings, especially #11. These seal the metering valve #10 which is operated by the trigger. If the metering valve is stuck in the open (trigger depressed) position, the gun will always be on.

terrye said:

I'd look closely at all the o-rings, especially #11. These seal the metering valve #10 which is operated by the trigger. If the metering valve is stuck in the open (trigger depressed) position, the gun will always be on.

Click to expand...

Terry, thanks for the comment. I did replace that o-ring with no improvement. That metering valve is actually after the trigger and is more like an internal flow restrictor. It is not operated by the trigger, but just adjustable from the back with a screwdriver.

Keep the ideas coming…