Yong Heng Pressure on gauge is not rising.

Hey guys, maybe someone has had this happen and can point me in the right direction. Got my compressor back in September and I have only used it 4 times to top off my tanks. I put compressor oil # 46 as instructed the day I got it. Ran it for about 20 minutes with really cold water flowing from my pool (endless supply). Before running the second time I changed the oil just to be safe. Has worked flawless until today. It started leaking out of the oil breather tube and not building any pressure. If I cover the breathing tube it does start to build pressure. Just looked at the oil and it’s really dark too. Not even half hour on that oil. I have looked at the flap valve and it did have some carbon but not much. Also looked at the other check valve with the spring and it is also good. I have time to take things apar and not afraid to do so. I usually shoot about 300 pellets a day and pumping is getting old for me. Any inputs of where to look at? Thanks in advance. 

Hey Racolon I know it's been a year but did u ever get ur Yong heng fixed. Mine is only 6 months old and has started doing the same thing as yours with only building to 2500-2800 psi and takes forever to do that. Also air rushing out oil cap hole and gauge dead. Any help would be greatly appreciated. Has worked great for first 6 months. 

Hey Racolon I know it's been a year but did u ever get ur Yong heng fixed. Mine is only 6 months old and has started doing the same thing as yours with only building to 2500-2800 psi and takes forever to do that. Also air rushing out oil cap hole and gauge dead. Any help would be greatly appreciated. Has worked great for first 6 months.

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I have experienced my Yong Heng failing to build up pressure several times and all were due to external leakage that can be detected by turning off the compressor and listen for hissing. The location can be detected by placing a finger next to each fitting or joint. The sound would change if the leakage occurs there. If the leakage is too small to produce any hissing, the compressor can always go to 4500 psi but the time taken will be significantly longer. Those small leakage can be detected by soap water. Dish washing liquid diluted with water works great.

It is normal for Yong Heng to have a small and continuous outflow of air from the breather tube but too much means that compressed air is leaking back to the crankcase. Suggest to check the piston rings.

The dead gauge can be replaced at very low cost.

Hey Racolon thanks for the speedy reply. Guess I've got a winter project..lol. Glad I've got my 9 liter SCBA tank for backup.

Hey guys I figured out what's wrong with YH. Air gauge burst cap. Replaced gauge and it's pumping like a champ!! Question is can that cap that came out be replaced or is gauge junk? Thought if I could repair it for a backup that would be good. Thanks again for advise!

Hi,

I finaly found time to do a service for my Yong Heng compressor. 

Cleaned everything ,replaced where needed o-rings and reassembled everything.

I allready openen it again to see if these little valve plates were in correct position.

My compressor only goes to 1500psi.

I put a stop in HP outlet to see how far it goes and did not open bleed valve to check for leaks, pressure remains the same in system.

What could it be,any suggestions?

Thanks and i hope to soon fill my new gun.

Hi,

I finaly found time to do a service for my Yong Heng compressor. 

Cleaned everything ,replaced where needed o-rings and reassembled everything.

I allready openen it again to see if these little valve plates were in correct position.

My compressor only goes to 1500psi.

I put a stop in HP outlet to see how far it goes and did not open bleed valve to check for leaks, pressure remains the same in system.

What could it be,any suggestions?

Thanks and i hope to soon fill my new gun.

Update:

Now 8hrs later pressure in system is tesame 1500psi. So no leaks.

I'm gonna try and change the high pressure piston seals. And again check these valve plates (found better pictures of them)

trevor5534 said:

Hey guys I figured out what's wrong with YH. Air gauge burst cap. Replaced gauge and it's pumping like a champ!! Question is can that cap that came out be replaced or is gauge junk? Thought if I could repair it for a backup that would be good. Thanks again for advise!

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trevor - did your fix above solve the air coming out of the breather tube? Is there a burst cap in the air gauge?

Mine fills my 45 minute SCBA tank a lot faster after I replaced an O-ring that was either above or below the second stage, I think it was between the stages where the paper gasket is. I was a bit afraid to tear mine down too but it got to where it would not fill my tank from ~3000 to ~4000 before it started to get hot. I did not like that so I took it apart to inspect it. Fortunately my issue was an O-ring and I had another one. I was looking in this area because I could feel a little air coming out at around this location. Still feels like there is, however, but the tank is filling pretty fast. Yesterday I got it close to 300 bar in 12 minutes.