Champion R15B Compressor Pumping Air Slower Than Rated Capacity
I have recently mounted a used Champion R15B compressor to an 80 gallon tank. It has a 16.5 inch flywheel and is attached to a 5 HP 220 Volt motor spinning at 3450 RPM. The electric motor has a 3.5 inch pulley. According to my calculations, this is spinning the compressor pump at approximately 730 RPM. The pump is listed at 710 RPM max, so not sure if this small percentage of increase has anything to do with it, but the compressor pump seems to be only delivering about half of rated capacity, or less. From zero to shut off at 125 psi, it takes 14 minutes to fill. At lower pressures, say up to 50 psi, it appears to be pumping at about 8 to 9 CFM, but after that it drops off, and the best I can tell by the time it gets between 100 and 125 psi, its probably only pumping about 6 CFM or less. This pump is rated at 16.5 CFM at 175 psi.
I can find no visible or audible air leaks. I removed all four valves, and cleaned and inspected those. Unfortunately they were not gunked up, and appeared to be in good condition, with no carbon deposits, just some sticky oil residue, which I cleaned off with gasoline, and reassembled. This did not help, really.
What I have done to troubleshoot:
1. Changed oil in compressor. ( 30 weight non detergent motor oil )
2. Tried running the compressor without air filter to see if any change. None noticed
3. Ran compressor without intercooler tube attached to check each piston. Both were functioning independent of the other.
4. Checked for belt slippage
5. Removed the tubes from governor housing to see if air was blowing right through while running. Lots of air flow through tube coming from high pressure port to governor
housing, as expected. But, air flow seemed minimal from governor housing back to intake manifold. So unless air is dumping back into the crankcase, I believe the unloader valve is functioning as designed.
6. It has an oil monitoring device on it. I disconnected the tube from governor housing and plugged it in case that was a source of escaping air. No change.
7. Removed the valves again, and put a couple of tablespoons of Marvel Mystery Oil on top of each piston and allowed to soak for 30 minutes or so, then soaked out with a paper shop towel. After reassembly, no noticible change. The best I could tell, the pistons and cylinder walls looked really clean and shiny.
8. Checked for excessive blow by in crankcase. The best I can tell, its minimal.
So, I am at my wits end and exhausted my knowledge as to why this compressor is not pumping much air. I had a B5900 pump mounted on it previously, that could fill the tank from zero pressure in about 8 or 9 minutes all the way up to 175 psi Same electric motor, just different pulley. The B5900 pump developed a reed valve problem or head gasket problem was why I changed out to begin with.
I may have to fix it if I can't get this Champion to pump much better.
Any ideas what may be wrong with the Champion R15B ??
Terry, I am in awe of your expertise with compressors. You should be writing this column, not me!
If the compressor rings are good, and air is being compressed, all I can think of that you haven't already examined is an internal gasket leak.
Good luck, and thank you for the detail. If there are compressor mechanics out there that have a comment on Terry's work, please post.