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EW4040 AAA Triplex Plunger 1” Shaft Pump 4400 PSI 4.0 GPM
| Part Number | EW4040 |
| Brand | AAA |
| Item Weight | 20 lbs |
| Mounting Orientation | Horizontal |
| Part Type | Pressure Washer Pump |
| Max Pressure | 4400 |
| Flow Rate | 4.0 |
| Inlet Size | 3/4” Garden Hose |
| Outlet Size | 3/8” QC |
| Shaft Size | 1” |
| Bolt Pattern | SAE |
| Drive Key Size | 1-1/2” x 1/4” |
| Oil Capacity | 12 fl oz. |
The AAA EW4040 is an industrial horizontal triplex plunger pump rated at 4,400 PSI and 4.0 GPM, designed for direct-drive gas-powered pressure washers with a 1" hollow shaft and SAE gas flange. Recommended for 9–13 HP engines, it features a fully anodized die-cast aluminum crankcase, ceramic-coated pistons, a 1/2" FPT garden hose inlet, and a 3/8" female brass quick-connect outlet.
- Wide Pressure Range with Built-In Chemical Injector u2014 Fully adjustable unloader with EZ-start system allows pressure regulation from 500 PSI up to 4,400 PSI; integrated downstream chemical injector enables on-demand soap application without additional fittings.
- Dual Oversized Ball Bearings with Ceramic-Coated Pistons u2014 Oversized radial ball bearings reduce friction under sustained high-load operation; ceramic-coated pistons extend seal life and resist pitting in demanding conditions.
- Oil Sight Glass with Pre-Installed Thermal Relief Valve u2014 Oversized sight glass provides immediate oil level and contamination visibility without a dipstick; pre-installed thermal relief valve protects the pump from heat damage, with a maximum operating temperature of 140u00b0F.
Part numbers 7109267 is another number used for the same product as EW4040. These are alternative part numbers used to identify this product.
| Alternate Part # | Equivalent To | Status |
|---|---|---|
| 7109267 | = EW4040 | Same Product |
This part is designed to work with the engine models listed above. Engine compatibility is based on shaft size, bolt pattern, and mounting orientation.
Each cylinder uses a two-stage seal stack to contain pressure around the ceramic plungers. Water inside the manifold head heats rapidly when the pump runs in bypass mode, and extended bypass operation—beyond two minutes—is enough to deform the rubber seals. Compromised seals allow water to escape through the weep holes on the underside of the pump head.
Remove the manifold, inspect the pressure seals for signs of damage and the ceramic plungers for hairline cracks. Replace the damaged components as needed.
The pump moves 4.0 GPM, meaning any debris that gets past the inlet screen can easily lodge in one of the six check valves. A valve that can't close fully allows water to backflow on the stroke, immediately destabilizing pressure. Fatigued check valve springs produce the same result without any debris present.
Remove the pressure valves in the manifold with needle-nosed pliers. Flush and clean out any debris that may be causing the blockage. If the valves are damaged replacements may be needed.
The EW4040 uses ceramic-coated plungers with a dual water packing stack. If the engine runs with the trigger released for more than 2 minutes, heat builds inside the brass head and degrades the rubber packings. Once the seals fail, water bypasses the plungers, enters the crankcase, and mixes with the oil — damaging the internal bearings.
Drain the oil and remove the manifold. Inspect the oil seals for scoring and other damages. If damage present, replace the seals and refill with oil.