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XRogerX
04-01-2007 20:31:07
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Re: qr 325 quincy compressor in reply to vidnru, 04-01-2007 17:22:04
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Anything above 15psi should be fine. You may have a sticky shuttle valve in the one of your crank throws. It is operated by centrifugal force to close an oil passage when the crank is spinning, then open it up again to bleed off oil pressure once the pump stops turning, so the hydraulic unloader opens the air valve to the heads to open the unloader valves. This shuttle valve is located on the crank counterweight nearest to the back of the compressor. It looks like a plain brass nut with a hole in the middle, It contains a simple shuttle and spring inside. if the shuttle cannot close the oil port when the compressor runs, you will get no oil pressure buildup. Alternately, the pump could be running the opposite way to how the oil pump is setup to operate. If this is a newer 325, there will be arrows on the rear bearing carrier to show which way the pump must turn for the oil pump to operate. Follow the arrow at the top of the bearing carrier. There is also a 1/4" pipe plug which must be present in the proper port inside the spin-on oil filter housing. If you have a slightly older 325 with the flat, hexagonal plate on the back, the oil pump has a moving sleev e ring in it which is supposed to self adjust for rotation, but in practice, it is often in too snug to rotate freely, so you can take off the plate and gently rotate the ring in the direction that the friction from the vanes would pull it in if was adjusting itself properly. A light hammer tap with a pin punch works for this. There is also a small o-ring on the back end of the crank which seals it to the oil pump and holds pressure inside the crankshaft. If it has perished, or was torn under reassembly, you will not get any oil pressure buildup. On some 325's there is an allen plug on the front counterweight which has a hole drilled through it to spay oil onto the front bearing. If this plug it missing, or the hole is too big, there will be little oil pressure. this all assumes that you have the oil pressure regulating setscrew turned in sufficiently far to allow oil pressure to build. If you look at the back of the pump, it is the bolt sticking straight out at 9:00 with the locknut on it. The oil strainer screen in the sump might also need cleaning, but that's not usually a problem. Of course, this doesn't mean that your hydraulic unloader ISN'T pooched, of course, but that has nothing to do with oil pressure, unless the seals are completely shot and it is allowing oil to dump directly back into the sump, instead of sealing it inside the valve actuator.
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