A. Water Supply
1. Check faucet. 4.0 gpm is required.
2. Outside diameter of hose should be 3/4”.
3. Maximum length of hose should be 50’.
4. The inlet water pressure should not exceed 90 psi.
5. Hose should not be kinked or damaged.
B. Nozzle
1. Check function and setting of original nozzle by using an in-house
nozzle. If pump functions properly with in-house nozzle but
malfunctions with original nozzle, replace nozzle.
C. Water Inlet Filter
1. Remove filter with pair of valve pliers. (figure 1)
2. Clean filter.
3. Replace filter if it is torn, bent or missing.
4. Reinstall filter.
Note: If water inlet filter is missing or damaged, further damage
may have occurred inside the pump.
D. Bypass Valve
1. Unscrew pressure volume control assembly. (figure 2)
2. Remove brass bushing. (figure 3)
Note that bushing is positioned with large side down.
3. Pull out bypass valve. (inset figure 3)
4. Inspect bypass valve for damage and lubrication.
Inadequate lubrication will cause valve to hang up.
5. Inspect O-rings for nicks or cuts. Replace if necessary.
6. Grease only large O-rings with lithium grease. (figure 4)
7. Replace bypass valve if necessary.
E. Safety Relief Valve
1. Unscrew the safety relief valve screw cap. (figure 5)
2. Remove spring, valve seat and ball. (inset figure 5)
3. Check for wear or pitting.
4. Replace valve if necessary.
5. If valve seat in the cylinder head is defective, the entire
safety relief valve must be replaced.
6. Reassemble and replace screw cap making sure ball is in seat.
Note: Pitting will occur if inlet filter is damaged or missing.
8
SECTION 1 / LOW WATER PRESSURE SOLUTIONS
A. Water Supply
B. Nozzle
C. Water Inlet Filter
D. Bypass Valve
E. Safety Relief Valve
figure 5
figure 1
figure 4
figure 2
figure 3
Large O-ring
Small O-ring
Pump 785 9/28/01 3:06 PM Page 8
www.mymowerparts.com
For Karcher Pressure Washer Parts Call 606-678-9623 or 606-561-4983