Frequently Asked Questions


We have compiled a list of the questions that are frequently asked, in the hope that it might be helpful to our customers. But don’t hesitate to contact us with any questions, comments or concerns — by email at, or by phone at 1-800-444-4351.

  1. Section

    Q: Why won’t my Paint Gun Washer start?

    There are several reasons why your washer might not start; we suggest you:

    1. Check that the air-line is properly connected with 90-120 psi.
    2. Check the lid, and ensure that it is fully closed.
    3. Make sure the limit valve (#M1C) on the valve bracket is closed in the downward position.
    4. Check all air connections to ensure that there are no leaks.
    5. Make sure the timer cam is engaging the limit valve (#M1C) on the pump housing assembly.
    6. Make sure the timer is on and functioning properly.
  2. Section

    Q: Why won’t my Paint Gun Washer shut off?

    There are several reasons why the washer won’t shut off:

    1. The timer cam (#M230-001A) may be jammed. If it is not is moving, slightly loosen the nuts holding the limit valve (#M1C) on the top panel of the pump housing assembly. Reposition valve and tighten nuts.
    2. The limit valve (#M1C) may be stuck in the open position. Please make sure it is closed.
  3. Section

    Q: Why is the pump leaking from its top bar?

    The manifold is probably cracked, but can be quickly replaced. Contact Herkules Customer Service for the replacement part (#1003560), or order online here.

  4. Section

    Q: Why is my 338 Pump not working?

    It could be one of several things: filter blockage, the air connection, the regulator, or the switches.

    1. Check the filter screen inside the tub/tank, and make sure it is clean and free of buildup.
    2. Check the air-line connection; make sure the psi line is not kinked or otherwise hampered from free air flow. Then check the connection; on the bottom of the M1C switch are two ports where the air-lines are attached. These air lines might be reversed. To change the lines; simply push down on the black ring around the port to release the line, then switch and re-connect.
    3. Check the Regulator: Unscrew the bowl on the bottom and make sure this bowl is clean. Make sure that the regulator is set to 75 psi; if it’s lower there is not enough power to operate the pump.
    4. Check the Switches: The M1C switch (slightly larger than a paper clip) controls air flow. When the top of the switch is depressed, air flows through the switch. Make sure the switch can open, and is not obstructed in anyway.
  5. Section

    Q: Why does the pump still operate after the timer has shut off?

    The blue and black air lines going to the M1C switch might be reversed (on backwards). Switch the lines, and see if this solves the problem.

  6. Section

    Q: My washer unit is great, but the pump is old; should I purchase a new unit, or can I upgrade the pump?

    Most new Herkules Paint Gun Washers use our powerful 338 Pump; this reliable unit can be retro fitted to most washers. In some instances, we provide kits that enable shops to repair their current pump, or convert it to the 338. Current and retired pumps are pictured, along with the kits available for each. To order a new pump, pump kit, or replacement manifold, visit

    Pump Convert/Rebuild/Replace Kit # needed
    338 Rebuild 338-KIT-01
    338 Replace 338
    318 Convert 12164
    318 Replace 318
    314 Convert 11972
    10686 Convert 11972
    10686 Rebuild 10792
    Piston Convert 11981
    338 Pump

    338 Pump

    318 Pump

    318 Pump

    314 Pump

    314 Pump

    10686 Pump

    10686 Pump

    Piston Pump

    Piston Pump


  7. Section

    Q: My Paint Gun Washer starts, but pumps slowly, or not at all.

    We suggest that you:

    1. Check the Intake Filter (#12491) to make sure it is not clogged. If it is, clean or replace.
    2. Check that the air-line is properly connected with 90-120 psi.
    3. Check all air connections to ensure that there are no leaks.
    4. Drain filter-regulator of water; see Preventative Maintenance in your manual for instructions.
    5. Check the solvent, there should be 5 gallons of clean solvent in the gun washer, with the solvent filled to an inch above the intake filter(#12491)
    6. Check that that lid is closing completely.
    7. Check the limit valve (M1C) on the valve bracket (M1SA) to make sure it is closed in the downward position.
    8. Check the manifold nozzles and stem supports and make sure they are not clogged.
  8. Section

    Q: Can I clean solvent paint guns with my Herkules waterborne gun washer?

    Only if you don’t want to use it again; Herkules waterborne gun washers are designed to handle the consistency of those paints, and solvent paints will clog and damage the waterborne lines. The G375 and G520 can accommodate both types of paints, because each paint type has a dedicated tank and line. While most Herkules washers can handle both waterborne and solvent, each washer must be dedicated to one paint type or the other.