Water Delivery System and 777F WTR, 777G WTR and 785D WTR OEM Off-Highway Trucks Caterpillar

Illustration 1	g03610786

Illustration 2	g03608581

The possible causes of this diagnostic code are listed below:

• Failed sensor

• Incorrect hose connection

• Failed water pump

• Failed hydraulic motor

1. Check Hydraulic Hose Connection

   1. Park the machine. Turn key start switch to the OFF position.

   2. Inspect the main hydraulic hose connection between the piston pump and motor.

   3. Inspect the signal and pilot/servo hose connection between the pump and motor.

      Note: Step 1c is important and the most commonly seen issue in the field.

   4. Turn the key start switch to the ON position. Start the engine, and let the engine idle.

   5. Select the "cannon" mode on the WDS keypad.

   6. Position the water cannon to spray into a remote location.

   7. Turn on the WDS water pump.

   8. Observe and compare the direction of rotation of the water pump shaft with the direction indicated on the water pump housing.

      Expected Results: The hoses are connected according to the schematics. The water pump direction of rotation is the same as indicated on the pump housing.

      Results:

      OK - Hydraulic hose connection and direction of pump rotation is OK. Proceed to Step 2.

      Not OK - The pump is turning in the opposite direction.

      Repair: Reconnect the piston pump and motor hoses according to hydraulic schematics. Check for the error code.

      STOP.

      Not OK - The signal and pilot/servo hose connection is not correct.

      Repair: Reconnect the signal and pilot/servo hose connection according to hydraulic schematics. Check for the error code.

      STOP.

2. Check WDS Oil Filter

   1. Park the machine. Turn the key switch to the OFF position.

   2. Remove the WDS oil filter.

   3. Cut open the filter and check for metal debris.

      Expected Result: The WDS oil filter is clean.

      Results:

      OK - No contaminant-related failure. Proceed to Step 3.

      Not OK - The filter has excess metal debris. The hydraulic pump or motor has failed.

      Repair: Replace the WDS hydraulic pump, hydraulic motor and charge pump. Flush the WDS hydraulic system.

      STOP.

3. Check Water Pressure Sensor

   1. Park the machine. Turn the key switch to the OFF position.

   2. Install a 376-4170 Pressure Sensor from the 368-9910 Multi-Tool Group in the water piping close to the WDS water pressure sensor.

   3. Turn the key start switch to the ON position. Start engine and let the engine idle.

   4. Select the "cannon" mode on the WDS keypad.

   5. Position the water cannon to a spray into a remote location.

   6. Turn on the WDS water pump.

   7. Observe the water pressure from the diagnostic pressure gauge and from the "Pressure Checks" measure group on the MD3 display.

      Expected Result: The water pressure at low idle in cannon mode is 414 kPa (60 psi).

      Results:

      OK - The measured water pressure is the same as the sensor pressure. Proceed to Step 4.

      Not OK - Water pressure measured by diagnostic pressure gauge is higher than the WDS sensor by 138 kPa (20 psi). The water pressure sensor has failed.

      Repair: Replace the water pressure sensor.

      STOP.

4. Check Hydraulic Pressure

   1. Park the machine. Turn the key switch to the OFF position.

   2. Install a 376-4170 Pressure Sensor from the 368-9910 Multi-Tool Group in the suction port of the WDS pump. This port is labeled "Ms". Install a 376-4171 Pressure Sensor from the 368-9910 Multi-Tool Group in the discharge port of the WDS pump. This port is labeled "Mp". The size of these ports is M14x1.5.

   3. Turn the key start switch to the ON position. Start engine and let the engine idle.

   4. Select the "cannon" mode on the WDS keypad.

   5. Position the water cannon to a spray into a remote location.

   6. Turn on the WDS water pump.

   7. Ensure that the WDS oil temperature is above 65° C (149° F).

   8. Observe the hydraulic pressure on the pressure gauges. Observe the hydraulic "Loop B psi" pressure from the "Pressure checks" measure group on the MD3 display.

      Expected Result: The suction port pressure is approximately 1862 kPa (270 psi). The discharge port pressure is between 20684 kPa (3000 psi) and 22063 kPa (3200 psi).

      Result: Suction pressure is in range, but discharge pressure is greater than 24132 kPa (3500 psi). The possible cause could be water pump or motor failure. Proceed to Step 5.

      Result: The hydraulic pressure measured by the diagnostic sensor and the system pressure sensor is out of range by 3447 kPa (500 psi). The hydraulic sensor has failed.

      Repair: Replace the sensor. Check for the diagnostic code.

      STOP.

5. Check WDS Water Pump

   1. Turn the key switch to the OFF position.

   2. Remove the WDS piston motor from the water pump, and rotate the water pump shaft manually.

   3. Check the suction sump and discharge of the water pump for debris. Remove the water pump if needed.

   4. Rotate the water pump shaft manually.

      Expected Result: No debris is present in the pump suction and discharge. The water pump shaft rotates freely.

      Results:

      OK - No debris is present in the pump suction and discharge. The water pump shaft rotates freely. Proceed to Step 6.

      Not OK - Debris is present in the pump suction or discharge.

      Repair: – Clean the water pump suction and discharge. Check for the error code.

      STOP.

      Not OK - The shaft does not rotate freely. The water pump has failed.

      Repair: Change the water pump. Check for the error code.

      STOP.

6. Check WDS Motor Case Drain Flow

   1. Park the machine. Turn the key switch to the OFF position.

   2. Connect a flow meter to the case drain of the WDS piston motor. The port size is M22x1.5. Use a 4C-9910 Portable Hydraulic Tester with a 4C-9911 Flow Meter Gp.

   3. Turn the key start switch to the ON position. Start engine and let the engine idle.

   4. Select the "cannon" mode on the WDS keypad.

   5. Position the water cannon to a spray into a remote location.

   6. Turn on the WDS water pump.

   7. Ensure that the WDS oil temperature is above 60° C (140° F).

   8. Observe the case drain flow.

      Expected Result: The measured case drain flow at low idle is approximately 15.1 L/min (4.0 US gpm).

      Results:

      OK - Contact product support.

      Not OK - If the measured case drain flow is greater than expected in the motor, then the WDS motor has failed.

      Repair: Change the WDS motor.

      STOP.