Compressor problem

rv9aviator · #1 02-10-2008, 07:14 AM

My air compressor is blowing a pop off valve right at the compressor head. It is a 75 PSI valve. It only blows when the compressor is running. The pop off valve on the tank does not blow and is a 175 PSI valve. I'm not even sure what the 75 PSI valve is protecting. This is a two stage compressor. I started to switch the valve with another one I had but decided not to since it is a 175 PSI valve. Any Suggestions?

Thanks

captainron · #2 02-10-2008, 07:50 AM

Quote:

Originally Posted by rv9aviator

My air compressor is blowing a pop off valve right at the compressor head. It is a 75 PSI valve. It only blows when the compressor is running. The pop off valve on the tank does not blow and is a 175 PSI valve. I'm not even sure what the 75 PSI valve is protecting. This is a two stage compressor. I started to switch the valve with another one I had but decided not to since it is a 175 PSI valve. Any Suggestions?

Thanks

Perhaps a reed valve stuck open or damaged that's allowing the second stage to blow-off (backfeed) the first stage pop-off valve?

rv9aviator · #3 02-10-2008, 08:48 AM

I think you're exactly right. After thinking about it I figured there must be a check valve or reed valve between the two stages. I'll pull the head and see what blew.

Thanks

airguy · #4 02-11-2008, 10:55 AM

Three possibilities, listed here in order of likelihood.

1 - the spring in the popoff valve has weakened with time and it's blowing at less than 75 - confirm with a pressure gauge in place of the valve.

2 - Checkvalve on the second stage (either input or output) is dropping the efficiency of the second stage and causing the air to "back up" in the first stage cooling loop. Usually this is just a remove/clean/replace type operation.

3 - The second stage piston/liner is shot and not compressing at all, turning your compressor into a single stage unit - same symptoms as #2, pull the head and rotate the crank to move the piston to the bottom of the liner, check the liner with a good light. If the wrist pin or rings are trashed you'll know it immediately, it should be a smooth mirror finish.

rv9aviator · #5 02-11-2008, 05:49 PM

Problem solved! The gasket went south and a piece of it stuck under one of the reed valves. I am ordering new gaskets but bought a new pump to get back in operation. A machine shop doesn't run without air.