Samson PumpMaster 3 55:1 Packing Set & O-Ring Repair Kit (GK2) #740951
| Part Number | 740951 |
| Kit Number | GK2 |
| Kit Type | Packing Set Repair Kit |
| Included Positions | 21–24 |
| Includes | O-Ring #21 and Packing Set Components #22–24 |
| Fits | Samson PumpMaster 3 55:1 Grease Pumps |
| Applicable Pump Models | 300, 302, 304 |
| Service Manual | 840803 / SM840803 |
Samson PumpMaster 3 55:1 Packing Set & O-Ring Repair Kit (GK2) #740951
Samson #740951, also identified as repair kit GK2, is the packing-set service kit for PumpMaster 3 55:1 air-operated grease pumps. Samson's service manual lists GK2 as the Packing Set repair kit and identifies it as covering pump positions 21 through 24.
The service procedure confirms that these components include the O-ring at position 21 and the packing-set components at positions 22 through 24. They seal the area between the air-motor and fluid sections of the pump and are replaced together during the packing repair procedure.
When This Kit May Be Needed
Samson's troubleshooting information identifies worn or damaged seals at positions 22 and 23, or damage to O-ring #21, as possible causes of grease bypassing into the air motor. These components are included in GK2.
- Grease has bypassed into the air-motor section
- Packing components #22 or #23 are worn or damaged
- O-ring #21 is worn, damaged, or incorrectly positioned
- The pump is being serviced according to Samson's packing-set repair procedure
A leak at the air outlet muffler can have more than one cause, so use the Samson troubleshooting procedure to identify the failure before replacing parts.
Kit Contents
| Position | Component |
| 21 | O-Ring |
| 22–24 | Packing Set Components |
Installation Notes
Samson instructs technicians to remove the existing packing set at positions 22–24 and O-ring #21, replace those components, and clean the O-ring seat before reassembly.
Assembly order is important: install O-ring #21 in its correct position inside the motor body first, followed by the large packing set and then the small packing set.
Follow Samson service manual 840803 for complete disassembly, pressure-relief, cleaning, inspection, and reassembly instructions.
Pump Compatibility
The PumpMaster 3 55:1 family includes Samson pump models #300, #302, and #304 for 35 lb, 120 lb, and 400 lb grease containers. The pump family is designed for grease up to NLGI-2 and uses a 55:1 pressure ratio.
Related PumpMaster 3 Repair Kits
- #740950 (GK1): Air motor repair kit, positions 1–20
- #740952 (GK3): High-pressure valve repair kit, positions 25–28
- #740953 (GK4): Foot valve repair kit, positions 30 and 35–38
- #740954 (GK5): Pressure check valve, high-pressure cylinder and piston kit, positions 25–34
Not sure GK2 is the correct repair kit for your PumpMaster 3? Call Alamo Equipment at (817) 865-3707 and we can help match the pump symptom to the appropriate Samson repair kit.
Part numbers: 740951, GK2
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