PULLEY-ALTERNATOR DRIVE 4N9325 - Caterpillar

This procedure checks the high-pressure pump when the rail pressure is 10 MPa (1450 psi) or higher and the engine does not start.The high-pressure fuel pump has two sides. This procedure checks the pumping capacity of each side.
Illustration 1 g02436860
Harness connectors for the high-pressure fuel pump
(1) Harness connector for side 1
(2) Harness connector for side 2
Refer to Illustration 1. Unplug the harness connector for side 1 (1).
Crank the engine for 10 seconds. Record the rail pressure.
Connect the harness connector for side 1 (1). Unplug the harness connector for side 2 (2).
Crank the engine for 10 seconds. Record the rail pressure.
Connect the harness connector for side 2 (2).
Record the rail pressures in Table 1. Put the higher rail pressure in the left column. Put the lower rail pressure in the right column. Perform the steps in the Table.
Table 1
Testing the Sides of the High Pressure Fuel Pump
Higher Rail Pressure Lower Rail Pressure
Step 1
Record the rail pressures.
Step 2
Multiply the higher rail pressure by 0.7. N/A
If the lower rail pressure is greater than the value in Step 2, the high-pressure fuel pump passes this test. Refer to the following example. In this example, the pump failed the test. The lower rail pressure is too low.
Table 2
Example of Testing the Sides of the High Pressure Fuel Pump
Higher Rail Pressure Lower Rail Pressure
Step 1
Record the rail pressures. 16 MPa (2300 psi) 10 MPa (1450 psi)
Step 2
Multiply the higher rail pressure by 0.7. 11 MPa (1600 psi) N/A
If the lower rail pressure is greater than the value in Step 2, the high-pressure fuel pump passes this test.
If the lower rail pressure is greater than the value in Step 2 of the table, the high-pressure fuel pump passes this test. If the lower rail pressure is less than the value in Step 2 of the table, replace the high-pressure fuel pump.