SPRING 1249861 - Caterpillar

Introduction
Table 1
Required Tools    
Tool     Part Number     Part Description     Qty    
A     278-4138     Cap Kit     1    Do not perform any procedure that is outlined in this Special Instruction until you understand the information that is contained in this document.Note: Plug or cap all open ports immediately with Tooling (A) .Note: Use a suitable container in order to collect any fluid loss.Procedure to Check the Pressure Relief Valve for Leakage
Illustration 1 g02680058
(1) Pressure Relief Valve (2) Fuel Return LineThe pressure relief valve (PRV) is located on the high-pressure rail. The PRV is designed to open when excessive pressure is generated. The PRV is to prevent failure of the high-pressure rail. During normal operation of the engine the PRV will not open. The opening of the PRV will cause a loss of fuel rail pressure. Use the following procedure to check the PRV for leakage.
Disable the fuel injectors using Caterpillar Electronic Technician (ET) and disconnect the injector wiring harnesses.
Disconnect the return to tank line (2) from the PRV. Plug or cap all open ports.
If any fuel is present in the PRV, then a clean cloth should be used in order to dry the valve.
Attach a length of clear plastic hose with an internal diameter of 20 mm (0.78740 inch) to the outlet of the PRV (1). Collect any fuel that leaks from the PRV in a suitable container.
Crank the engine for 10 seconds. Observe the outlet of the high-pressure relief valve (1). If any fuel is discharged from the outlet, then immediately stop the test and replace the valve. If no fuel is discharged, then the pressure relief valve is operating correctly.
When replacing the pressure relief valve, refer to the following procedure.
If the pressure relief valve is torqued at position (X), the pressure relief valve will be damaged.
Illustration 2 g01729253
Typical example
Use a 27 mm (1-1/16 inch) deep well socket in order to tighten the pressure relief valve to a torque of 120 N m (89 lb ft).Note: The pressure relief valve is a two-piece valve that should not be disassembled.