DeWalt DP3750 Pressure Washer Operation

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This guide is a handy illustrated step by step summary of the proper operation of the DeWalt DP3750 Pressure Washer. This guide was compiled from information found in the pump and (Honda) engine operating manuals supplied with the DeWalt DP3750 Pressure Washer. While every effort has been made to be thorough, this guide is not meant to be a substitute for reading those manuals.

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The Guide

1. This is meant as a summary. READ THE MANUALS BEFORE OPERATING THE PRESSURE WASHER!
2. Pre-startup: Do the following before starting the Pressure Washer engine.
1. Verify the water supply you will use to feed the Pressure Washer can deliver at least 5gals/minute @ 20PSI. If you can fill a 5 gal paint bucket in less than 1 minute then the supply should be okay. ONLY USE COLD WATER! HOT WATER WILL DAMAGE THE PUMP.
2. ONLY USE OUTDOORS! THE ENGINE GENERATES CARBON MONOXIDE GAS!



3. Check the pump oil level. Use the sight glass on back of the pump (Fig. 1). The correct level is up to the center dot. Add DP-70 pump oil if necessary.
4. Check the engine oil level using the dipstick (Fig. 2). Un-screw the dipstick, remove it and wipe it clean. Insert without screwing it in then pull it out to measure the level. Add 10W30 oil with an API rating SJ, SL Screw the dipstick back in.
5. Check and fill the gas tank (Fig. 3). Leave ½-1 inch at the top of the gas tank to allow for expansion. Use 86 Octane or higher. Wipe up spilled fuel. GASOLINE IS HIGHLY FLAMMABLE AND EXPLOSIVE! STOP ENGINE WHEN REFUELING AND AVOID SPILLS!





6. Verify filter screen is in water inlet of pump with cone side facing out and that the filter is clean (Fig. 4). Clean by removing and flushing with water in both directions.
7. Connect water hose to water source and turn on to remove air from hose. When a steady stream of water is present, turn off the water and connect hose to water inlet of pump (Fig. 5).
8. Connect high pressure hose to pump outlet (Fig. 5).
9. NEVER MOVE THE PRESSURE WASHER BY PULLING ON THE HOSES.
10. Turn on water source.
11. Depress trigger on spray wand (aprox 2 min) until a steady stream of water is present to remove air from pump and high pressure hose (Fig. 6). Air in the pump causes cavitation. The hammering noise will be the pump self destructing. BE SURE TO REMOVE ALL AIR FROM THE SYSTEM!









12. ALWAYS TURN OFF THE ENGINE BEFORE CHANGING NOZZLES. Attach the nozzle you want to use (see the chart). To attach the nozzle, pull quick-connect coupler back and insert nozzle (Fig. 7). Release quick-connect coupler and twist nozzle to make sure it is secure in coupler. IF THE NOZZLE IS NOT SECURE IN THE COUPLER IT CAN BECOME A DANGEROUS FLYING OBJECT WHEN YOU APPLY THE TRIGGER. AIM AWAY FROM PETS, PEOPLE AND BREAKABLES.
13. To apply cleaning chemicals or soaps, attach the clear chemical siphon hose (S) to the barbed fitting near the in/outlets of the pump (Fig. 8). Place the end with the filter into the container of cleaning chemicals/soaps. Use only soaps and chemicals designed for pressure washers. One gallon of cleaning solution is used for every 7 gallons of water. You must use the BLACK LOW PRESSURE NOZZLE to dispense chemicals/soaps, the others will not work. DO NOT USE BLEACH.
14. Wear safety glasses, hearing protection and suitable clothing.
3. Starting the Pressure Washer engine:



1. Move the fuel valve lever to the ON position (Fig. 9).
2. To start a cold engine, move the choke lever to the CLOSED position (Fig. 10). To restart a warm engine, leave the choke lever in the OPEN position.



3. Set the Throttle lever to about ⅓ of its MAXimum (Fig. 11).
4. Turn the engine switch to the ON position (Fig. 12).



5. Start the engine. Pull the start grip lightly till you feel resistance, then pull briskly (Fig. 13). Return the starter grip gently. TO PREVENT DAMAGE TO THE STARTER, DO NOT ALLOW STARTER GRIP TO SNAP BACK AGAINST THE ENGINE.
6. If engine does not start in two pulls, squeeze trigger of the spray gun to relieve pump pressure.
7. If the choke lever has been moved to the CLOSED position to start the engine, gradually move it to the OPEN position as the engine warms up.
4. Using the Pressure Washer:
1. WASHER OPERATES AT FLUID PRESSURES AND VELOCITIES HIGH ENOUGH TO PENETRATE HUMAN AND ANIMAL (PET) FLESH WHICH COULD RESULT IN AMPUTATION, FLUID INJECTION, OR OTHER SERIOUS INJURY. DO NOT TREAT FLUID INJECTION AS A SIMPLE CUT! SEE A PHYSICIAN IMMEDIATELY.
2. THE HIGH PRESSURE SPRAY CAN DAMAGE SURFACES SUCH AS WOOD, GLASS, SIDING, AUTOMOBILE PAINT, AUTO STRIPING AND TRIM, AND DELICATE OBJECTS SUCH AS FLOWERS AND SHRUBS. Start with lower pressure nozzles and work up to the proper cleaning strength to avoid damage. To lower pressure:



• Back away from surface being cleaned.
• Change to the 40° (white) nozzle.
• Adjust the pressure regulator knob. Turn the pressure regulator knob (R) counter-clockwise to lower the pressure (Fig. 14). The minimum pressure is in the 500-700PSI range. Return to full pressure when done. Do not turn past built-in stop or pump damage can result.
3. When you pull the trigger, the force of the spray can cause the gun to kick. Be sure you are prepared and in a stable position, DO NOT USE FROM A LADDER.
4. Depress trigger on gun to start water flow. Release trigger to stop water. Engage trigger lock (W) when gun is not in use to prevent accidental spraying (Fig. 15).



5. YOU MUST SPRAY WITHIN TWO MINUTES TO PREVENT TEMPURATURE BUILD-UP THAT CAN DAMAGE THE PUMP. IF THE THERMAL RELIEF VALVE (T) IS RELEASING WATER THEN THE WATER IN THE PUMP IS HOT ENOUGH TO DAMAGE THE SEALS (Fig. 16). IF YOU AREN’T SPRAYING TURN OFF THE PRESSURE WASHER.
6. NEVER TURN OFF THE WATER SOURCE WHILE PRESSURE WASHER IS RUNNING.
7. If engine is labored or sounds like it will stall then increase the throttle lever higher until operation is smooth.
8. If the Pressure Washer pulsates, there may be a clog in the nozzle. Shutdown and squeeze the trigger to relieve any pressure then remove the nozzle. Use the wire cleaning tool (Z) to remove any obstruction and then back flush with clean water (Fig. 17). Remove and back flush spray wand for 30 seconds also. Reassemble and test.
5. Shutting Down the Pressure Washer:
1. If chemicals were applied, place the clear chemical siphon hose (filter end) into a container of clean water and draw the clean water through the chemical injection system to rinse system thoroughly. PUMP CAN BE DAMAGED IF CHEMICAL IS NOT THOROUGHLY FLUSHED.
2. Return Pressure Regulator knob (Fig. 14) to full pressure if it was adjusted. Turn clockwise.
3. Set the throttle lever (Fig. 11) to the MINimum position.
4. Turn the engine switch (Fig. 12) to the OFF position.
5. Move the fuel valve lever (Fig. 9) to the OFF position.
6. Turn water source off.
7. Pull trigger on spray gun to relieve any pressure in hose or gun.
6. This summary is not a substitute for reading the manuals. READ THE MANUALS BEFORE OPERATING THE PRESSURE WASHER!
7. Get help at 1-800-4DeWalt (1-800-433-9258)

Download this Guide

Download this guide as a PDF: DeWalt DP3750 Pressure Washer Illustrated Operation Guide PDF