I know everyone is tired of hearing about my difficulties with my new Yeng Hung pump. Now I have got it running cool and broken in, but I get no change in pressure from the gauge attached to the pump or into the cylinder I'm filling. When I go back to my hand pump, I get an increase on the pressure of the gauge on the rifle and the hand pump gauge. I have tightened all of the fittings including the gauge and the and the outlet hose and removed the water filter as a troubleshooting measure, no change in pressure, what gives? Please help!
Yong heng
- Thread starter dark1961
- Start date
Sounds like it is not outputting any air at all. Is that the case? Can you just stick your thumb over the end of the hose while it starts up and confirm that there is no air coming out of it? Also, can you confirm that it shakes alot when you run it (it should, if not then your motor isn't turning the crank shaft or the crank shaft isn't moving the piston).
If you have tightened all the fittings and closed the vent valve tightly (and the cyclone water vent on the first stage separator oi your model has one), then the problem is somewhere inside the pump.
If you have tightened all the fittings and closed the vent valve tightly (and the cyclone water vent on the first stage separator oi your model has one), then the problem is somewhere inside the pump.
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I'd say a 200cc rifle should only take a minute or two to fill up - it's quick.
On most YH models, the outlet of the first stage piston goes to an aluminum block mounted on the side of the pump then back to the inlet of the second stage piston. That aluminum block is a cyclone separator that helps remove water from the air before it gets further compressed in the second stage. The base model YH does not have this, but the other models do. There is a vent valve toward the bottom on that block as well as a relief valve (brass valve with a pull ring). Both need to be closed or you will leak air from them while running.
On most YH models, the outlet of the first stage piston goes to an aluminum block mounted on the side of the pump then back to the inlet of the second stage piston. That aluminum block is a cyclone separator that helps remove water from the air before it gets further compressed in the second stage. The base model YH does not have this, but the other models do. There is a vent valve toward the bottom on that block as well as a relief valve (brass valve with a pull ring). Both need to be closed or you will leak air from them while running.
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I have put teflon tape on outlet hose fitting, the base of the pump gauge, and the pressure relief screw, I've got to have a leak somewhere, but I can't find it.
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Are you getting any pressure? Mine would stop building around 1000psi. A spring was broken at the low pressure check valve 
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Mine has worked great until yesterday. Tore 95 % of it apart and both pistons, rings, reed tab, and last check valve inthe top, below burst disc all look good. I didn't take the inner fitting out that holds the low pressure check valve. (didn't know it was in there). I'll look soon & let you know what I find. Any other hidden valves? Thanks for the pic & tip Csexton, it might help both of us. Good luck dark1961. Don't be afraid to open things up, pretty simple design, just dont over tighten your front case bolts. Case is aluminum
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Gave up troubleshooting the pump, took it to a place called "Roys Electric" here in Richmond, Virginia and had it fixed, six blocks from my house!!! $100
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