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Thread: Help please, compressor not working properly

  1. #1
    Join Date
    Mar 2003
    SF Bay Area

    Help please, compressor not working properly

    I have an old Grizzly 2hp compressor (model G8889) that is not working properly. After many years of pumping up to 120 lbs, it now all of a sudden pumps up to only about 70 lbs. The motor keeps running, as if it is trying to pump up higher. The only clue I have is that I had put it in my car and took it to another location, after that trip it hasn't worked properly. I'd appreciate any help I can get. Thanks. -Howard

  2. #2
    Join Date
    May 2009
    N.W. Missouri
    Sounds like a reed valve in the pump head is failing to seal and probably needs to be replaced.


  3. #3
    Many ~2hp compressors have reed valves in the head. Reed valves are usually sheet metal that flexes open or closed over a port. If the sheet metal fatigue cracks along the flex area, you will lose some or all of the seal, limiting the ability to store the air compressed by the piston.

    Other possibility is a relief valve is cracking too soon, a check valve from compressor to the tank inlet is not seating, the belt is slipping, or the drain valve was left open.

    Many malfunctions you will hear when you unplug the compressor and the air bleeds from whatever is leaking. Obviously a slipping belt will not leak-down.

    Edit: looks like you have a direct drive compressor, no belt to slip

    Have a look here:
    035 P8694035 Valve Gasket
    036 P8694036 Valve Plate
    037 P8694037 Check Valve
    038 P8694038 Valve Inner Gasket
    039 P8694039 Valve Plate
    040 P8694040 Cylinder Head Gasket
    106 P8694106 One-Way Check Valve
    114 P8694114 Safety Relief Valve
    Last edited by Paul Murphy; 07-12-2015 at 12:00 PM.

  4. #4
    Join Date
    Mar 2003
    SF Bay Area
    Thanks for this. The compressor holds pressure when the motor is off and the air outlet valve is shut. I don't exactly know how to figure out which item is faulty, but I'll have a go at it. -Howard

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