Simpson ALH4240 4200 PSI 4.0 GPM 60688 Pressure Washer

4200 PSI Gas Pressure Washer with Honda GX390 Engine and CAT Triplex Pump Three things tell a contractor everything they need to know about a pressure washer before they even touch it: the engine, the pump, and the frame. The Simpson ALH4240 checks all three without compromise. A Honda GX390 commercial engine that starts on the first pull and runs all day, a CAT Pumps triplex plunger pump rated for 4200 PSI at 4.0 GPM, and an aircraft-grade extruded aluminum frame that simply does not rust. You already know what those names mean. That's the point. Put those specs together and you get 16,800 cleaning units, enough to handle deck restoration, fleet washing, graffiti removal, and heavy-duty surface prep without ever switching machines. Whether you're running one job a week or putting this thing through five days of commercial work, the ALH4240 is sized and built to keep pace. Rated 4.8 stars across hundreds of verified buyers, it's a machine that consistently earns its keep in the field. Keep reading for the full breakdown, or scroll down to the Downloads section for the spec sheet, manual, and parts manual. And if you have questions before buying, our team is here to help you make the right call. Simpson ALH4240 Pressure Washer: Features and Highlights Honda GX390 commercial engine: 389 cc, 13 HP gross output, recoil pull-start, built-in low-oil shutdown alert. The Honda GX390 pressure washer engine is the benchmark in this class for a reason: it starts reliably, runs smoothly under load, and carries a 3-year commercial warranty. CAT Pumps triplex plunger pump (Model 67DX): 4200 PSI at 4.0 GPM, direct drive. The CAT pump pressure washer pairing means you're working with a commercial-grade pump that carries its own 5-year commercial warranty. External easy-start unloader and thermal relief valve included. 16,800 cleaning units: 4200 PSI times 4.0 GPM. That number is what actually determines how fast and thoroughly a machine cleans. Most jobs in this class don't require you to dial anything back. Aircraft-grade aluminum frame: brushed extruded tubing, corrosion resistant, built to outlast the pump and the engine. Where steel frames rust from the inside out, the aluminum frame pressure washer structure just keeps going. Simpson backs it with a 10-year commercial warranty. 50-foot steel-braided Monster Hose: 3/8 in. diameter, polyurethane outer jacket, kink and abrasion resistant, quick-connect fittings on both ends. Serious reach without the mess of a hose that fights you every time you coil it. 5 quick-connect nozzles: 0°, 15°, 25°, 40°, and soap (black). Swap tips in seconds without touching a wrench. The soap nozzle activates the downstream chemical injection for low-pressure detergent application. Ergonomic rear-load spray gun: safety trigger lock included, quick-connect fitting, designed for extended use without hand fatigue. 31-inch quick-connect spray lance: keeps your hands well back from the surface and pairs with all five included nozzles. 13-inch premium pneumatic tires: roll over job-site terrain without the headache of flat tires or hard plastic wheels that won't move over anything but smooth concrete. 1.6-gallon fuel tank: adequate runtime between fills for extended sessions. Runs on regular unleaded, minimum 87 octane, up to 10% ethanol (E10). Cold water only: not rated for hot water input. Water supply minimum: 5 GPM at 20 PSI. 49-state compliant: not for sale in California. Dimensions: 38 in. L × 23.5 in. W × 29 in. H (96.5 cm × 59.7 cm × 73.7 cm). Weight: 133 lbs (60.3 kg). The ALH4240 Pressure Washer: Frame, Hose, and Field-Ready Design The frame is where most pressure washers eventually lose. Steel frames corrode from road salt, fertilizer runoff, and plain old moisture, and once the corrosion starts, it doesn't stop. Simpson built the ALH4240 around an aircraft-grade aluminum frame, specifically extruded tubing that's been brushed for finish and sized for rigidity. That 10-year commercial frame warranty isn't marketing language: it reflects a design choice that takes the rust problem off the table entirely. If you're comparing aluminum frame pressure washers in this class, this is the one built to still be standing when the pump eventually needs attention. The hose and spray kit match the machine's professional intent. The 50-foot steel-braided Monster Hose with its polyurethane jacket gives you serious reach and resists the kinking and abrasion that kills cheaper hoses fast. The ALH4240 manual covers full maintenance intervals, and the Simpson ALH4240 parts manual is available in the Downloads section below if you're stocking up on Simpson 60688 parts ahead of heavy use. Quick-connect fittings throughout mean you're not threading anything by hand in the field. What's Included Simpson ALH4240 pressure washer machine Honda GX390 engine (installed) CAT Pumps Model 67DX triplex plunger pump (installed) 3/8 in. × 50 ft steel-braided Monster Hose with quick-connect fittings Rear-load ergonomic spray gun with safety trigger lock 31 in. quick-connect spray lance 5 quick-connect nozzles: 0°, 15°, 25°, 40°, and soap (black) Downstream chemical injection siphon tube Specifications: Simpson ALH4240 (60688) Brand Simpson Manufacturer Simpson Cleaning Model Number ALH4240 / 60688 Machine Pressure (max) 4200 PSI (289.6 bar) Flow Rate 4.0 GPM (15.1 L/min) Cleaning Units 16,800 CU Drive Type Direct drive Water Temperature Cold water only Water Supply Required Min 5 GPM at 20 PSI Fuel Type Regular unleaded, min 87 octane, max 10% ethanol (E10) Fuel Tank Capacity 1.6 gal (6.1 L) Engine Engine Honda GX390 commercial series Displacement 389 cc Horsepower 13 HP (gross) Starting System Recoil pull-start Low Oil Alert Shutdown included Pump Pump CAT Pumps triplex plunger, Model 67DX Unloader External easy-start unloader (adjustable) Thermal Relief Valve Included Hose and Accessories Hose 3/8 in. × 50 ft (0.95 cm × 15.2 m) steel-braided Monster Hose, polyurethane jacket, QC fittings Spray Gun Rear-load ergonomic gun, QC fitting, safety trigger lock Lance 31 in. (78.7 cm) QC spray lance Nozzles 5 quick-connect: 0°, 15°, 25°, 40°, soap (black) Chemical Injection Downstream siphon tube (low-pressure via soap nozzle) Physical Frame Aircraft-grade aluminum, brushed extruded tubing Tires 13 in. (33 cm) premium pneumatic Dimensions (LxWxH) 38 in. × 23.5 in. × 29 in. (96.5 cm × 59.7 cm × 73.7 cm) Weight 133 lbs (60.3 kg) Warranty Engine Warranty 3 years commercial Pump Warranty 5 years commercial Frame Warranty 10 years commercial Accessories Warranty 90 days Compliance and ID Compliance 49-state compliant. NOT FOR SALE IN CALIFORNIA. Part Number 60688 Online Model Number ALH4240-S UPC 879399001345 Downloads Simpson ALH4240 60688 Pressure Washer Spec Sheet Simpson ALH4240 Pressure Washer Quick Start Guide Simpson ALH4240 Use and Care Manual Simpson ALH4240 Parts Manual