Replacement of elements of the fuel system Cummins ISF3.8

This article covers the removal, inspection and installation of the engine fuel system components.

Replacement of the high-pressure fuel pump

1. Disconnect the battery negative terminal.

   

2. Disconnect the supply and return pipes from the high-pressure fuel pump.
3. Disconnect the supply line from the high-pressure fuel pump to the rail and loosen the mounting of the support brackets.
4. Disconnect the wiring harness connector of the fuel metering valve.

   

5. Unscrew the three mounting bolts of the high-pressure fuel pump.
6. Remove the fuel pump from the timing gear housing.

Disassembly of the high-pressure fuel pump

Disassembly involves only the replacement of the pump drive.

1. Using the fuel pump gear replacement tool (No. 4919109) and a 1/2 inch wide pry bar, hold the high-pressure fuel pump drive gear in place.

   

2. Loosen the fuel pump drive gear mounting nut by turning it anticlockwise. Do not remove it from the shaft.

   

3. Install the Snap-On TM bearing removal tool (No. CJ951) between the fuel pump mounting flange and the drive gear. Secure the bearing removal tool.
4. Install the Snap-On TM puller (No. CG150) on the Snap-On TM bearing removal tool (No. CJ951) and the fuel pump drive shaft.

   

5. Turning the puller screw, separate the gear from the drive shaft.
6. Remove the gear mounting nut, the lock washer and the gear from the fuel pump drive shaft.

Assembly of the high-pressure fuel pump

1. Before assembly, clean and dry the drive shaft nose and the drive gear seating surface. Wipe the shaft and gear with a lint-free cloth moistened with solvent. Do not touch the seating surfaces after wiping.

   

2. Install the drive gear on the drive shaft, the lock washer, and screw on the gear mounting nut by hand.

   

3. Holding the gear from turning with the puller, tighten its mounting nut. Tightening torque: 105 N·m.

Installation of the high-pressure fuel pump

Note: synchronisation of the fuel pump with the crankshaft is not required.

1. Install the fuel pump on the timing gear housing.
2. Screw in the fuel pump mounting bolts. Tightening torque: 25 N·m.

   

3. Install the high-pressure fuel line from the high-pressure fuel pump to the rail and tighten the retainers.

   Note: hold the high-pressure pump outlet union with a second spanner to avoid exceeding the tightening torque. Tightening torque: 21 ± 4 N·m.

4. Connect the wiring harness connector of the fuel metering valve.
5. Install the fuel supply pipes.
6. Install the return pipes.
7. Connect the leads to the battery terminals.
8. Fill the system with fuel.

Inspection and replacement of the fuel metering valve

Measure the resistance of the fuel metering valve. The maximum resistance must be 5 Ω.

Removal of the valve

1. Disconnect the connector.
2. Unscrew the three bolts.
3. Remove the metering valve by turning and pulling it outwards.

   

Installation of the valve

1. Fit a new O-ring on the fuel metering valve. Lubricate the new O-ring with clean oil.
2. Install the fuel metering valve by turning it and inserting it flush with the high-pressure pump seating surface. Tightening torques:
   • first stage: 3 N·m;
   • second stage: 7 N·m.
3. Connect the connector.

Injectors

Checking the fuel return

Note: faulty injectors cause excessive fuel leakage through the return line.

For engines with a quick-release coupling of the rail pressure relief valve, use the appropriate drain hose and plug to block the flow of fuel through the pressure relief valve.

1. Disconnect the quick-release coupling from the pressure relief valve.
2. Connect the pressure gauge adapter (No. 4918462) to the fuel accumulator pressure relief valve and drain the fuel into a container.
3. Install the quick-release plug (No. 4918464) on the fuel return hose to prevent fuel from entering the return line.
4. Start the engine. Activate the “Fuel Leakage Test” mode on the INSITE diagnostic tool and allow the operating temperature to rise for 1 minute. At elevated temperature, greater measurement accuracy is achieved.
5. Place the drain hose (No. 4918462) in a measuring container and measure the amount of fuel drained in 1 minute.

Normative fuel leakage values:

• INSITE diagnostic tool “Fuel Leakage Test” mode activated: less than 200 ml/min;
• Idle (leaks may be absent): less than 120 ml/min;
• Cranking the engine: less than 90 ml/min.

If the fuel leaks exceed the maximum value, the fuel return on one of the injectors must be blocked in order to localise the cause of the excessive leaks.

6. With the engine stopped, remove the high-pressure fuel line of the first cylinder.

   

7. Install the plug (No. 4918860) on the fuel accumulator union where the high-pressure line of the first injector is secured. Tightening torque: 30 N·m.
8. Repeat the leak check and record the result.
9. Install the high-pressure fuel line.
10. Repeat the leak check by disconnecting the other injectors in turn.

    

Determine which injector is leaking (with the faulty injector blocked, the leaks are minimal). If the leaks are approximately equal, several injectors are probably damaged.

Removal of the injectors

1. Disconnect the connectors from the injectors.
2. Disconnect the high-pressure fuel lines from the injectors and from the fuel rail.

   Note: clean all connections before disassembly. The ingress of dirt or debris can damage the fuel system.

3. Unscrew the nut and disconnect the No. 4 high-pressure fuel line from the fuel accumulator.
4. Unscrew the nut and disconnect the No. 4 high-pressure fuel line from the No. 4 injector.

   

5. Repeat the procedure for the other injectors. Cover all open ports with caps.
6. Remove the cylinder head cover.
7. Remove the injector return line.

   Note: mark the installation locations of all retainers and gaskets of the return fuel lines so that they can be installed in the places from which they were removed during assembly.

   

8. Remove the injectors:
   • unscrew the injector wiring mounting nuts, remove the leads;
   • loosen and unscrew the injector retainer bolt;
   • a pry bar with a small shoe may be used to remove the injector;
   • lift the injector by the clamping flange (the part of the injector body located slightly above the cylinder head casting);
   • remove the injector retainer;
   • remove the injector from the cylinder head.

Inspection of the injectors

1. Clean the injector in an ultrasonic bath with an aqueous solution.
2. Check the condition of the injector parts for damage.
3. Fit a protective cap on the injector nozzle.

   

Note: as a result of overheating, the nozzle becomes brownish-yellow or blue, which leads to injector damage, depending on the degree of overheating.

4. Check the resistance at the injector terminals. Nominal resistance: less than 3 Ω.

Installation of the injectors

1. Check the thickness of the new copper sealing washer. Nominal thickness: 2.5 mm. Do not install two copper washers!
2. Remove dirt around the injector bore.
3. Lubricate the injector O-ring with engine oil.
4. If the injector is in good order, install it in the place from which it was extracted.
5. Fit the retainer on the injector before installing the injector in the bore.
6. Orient the injector correctly in the cylinder head (fuel union towards the high-pressure line connector).
7. Using the transport cap of the upper part of the injector, make sure it is correctly seated.
8. Screw on the injector retainer mounting bolt.
9. Install the other 3 injectors.

   

10. Install the cylinder head cover without seals.

    

11. Tighten one screw on each side of the cover.
12. Connect the high-pressure line to the injector. Using the line nut as a guide, centre the injector in the seal.
13. Remove the high-pressure line from the injector and repeat for the other injectors.

    

14. Remove the cylinder head cover.
15. Tighten the injector retainer mounting bolts evenly in several passes.

    Note: tighten the bolts alternately by turning them 90° until the nominal tightening torque is reached. Tightening torque: 33 N·m.

    

16. Connect the injector leads and screw on the nuts. Tighten the nuts.

    Note: route the injector leads so that they do not touch each other or the rocker arms. If a rocker arm touches the injector wiring, the wiring insulation will be damaged, which will cause diagnostic codes to appear. Tightening torque: 1.5 N·m.

17. Install the cylinder head cover.
18. Connect the high-pressure fuel lines.

    

19. Loosen the fuel rail mounting bolts. Do not remove the fuel rail! The bolts are loosened to ensure the correct orientation of the fuel rail after installing the high-pressure lines.
20. Install and hand-tighten the high-pressure line nuts.

    

21. Tighten the high-pressure line nuts. Tightening torque: 22 N·m.

    

22. Tighten the fuel rail mounting bolts. Tightening torque: 24 N·m.
23. Connect the leads to the battery.
24. Start the engine and make sure there are no leaks.

Removal and installation of the fuel rail

1. Disconnect the battery negative terminal.
2. Remove the high-pressure fuel lines.
3. Unscrew the nut and disconnect the No. 4 high-pressure fuel line from the fuel accumulator.
4. Unscrew the nut and disconnect the No. 4 high-pressure fuel line from the No. 4 injector.
5. Repeat the procedure for the other injectors. Cover all open ports with caps.

   

6. Disconnect the fuel pressure sensor connector. Note: do not remove the fuel pressure sensor, as it will need to be replaced if removed.

   

7. Remove the fuel return line from the pressure relief valve.

   

8. Disconnect the high-pressure fuel line connecting the high-pressure pump and the rail from the fuel rail.

   

9. Unscrew the fuel rail mounting bolts.

   

10. Remove the fuel rail.

Installation of the fuel rail

1. Install the fuel rail on the engine.
2. Hand-tighten the fuel rail mounting bolts.
3. Connect the high-pressure line from the high-pressure pump to the fuel accumulator.

   Note: hold the union to prevent it from turning. Tightening torque: 30 N·m.

   

4. Install the high-pressure lines on the injectors and the fuel rail.

   

5. Tighten the fuel rail mounting bolts. Tightening torque: 24 N·m.
6. Connect the fuel pressure sensor connector.
7. If removed, install the fuel pressure sensor. Tightening torque: 70 N·m.
8. Connect the fuel return line to the pressure relief valve.
9. If removed, install the pressure relief valve. Tightening torque: 100 N·m.
10. Connect the leads to the battery.
11. Start the engine and make sure there are no leaks.

Pressure relief valve

Checking the pressure relief valve

1. Remove the quick-release connector from the pressure relief valve and fit the pressure gauge adapter (No. 4918462) in its place.
2. Install the quick-release blanking connector (No. 4918464) on the drain line disconnected from the pressure relief valve.
3. Place the end of the drain hose in a measuring container.
4. Activate the fuel system pressure check in the INSITE TM diagnostic tool or let the engine run at idle.
5. Place the other end of the drain hose or pressure gauge adapter in the container and measure the flow rate.

Technical requirements:

• At idle: no flow;
• When the INSITE TM diagnostic tool check is activated: maximum fuel flow of 16 ml per minute.

Note:

• If too much fuel flows from the pressure relief valve, restart the engine and set a high idle speed. The engine management system will attempt to eliminate the problem by means of the valve.
• If fault codes 449, 1911, 2311, 272, 553 or 2216 appear, do not replace the pressure relief valve until the cause of the failure has been determined.

Removal and installation of the pressure relief valve

1. Unscrew the pressure relief valve.
2. Clean the contact surfaces of dirt.
3. Screw in the pressure relief valve. Tightening torque: 100 N·m.

Fuel filter

Removal and installation of the fuel filter

1. Disconnect the connector from the water presence sensor.
2. Loosen and remove the fuel filter.
3. Make sure the O-ring has not stuck to the fuel filter head. Remove the O-ring if necessary.

   

4. Lubricate the O-ring with clean oil.
5. Install the fuel filter on the filter head.
6. Screw in the filter until it contacts the head.
7. Using a filter wrench, tighten the filter by 3/4 of a turn. Tightening torque: 23 N·m.

Note: do not pre-fill the fuel filter with fuel.

8. Prime the low-pressure fuel system using the hand pump (140–150 strokes for a dry filter).
9. Start the engine.
10. If the engine does not start within 30 s, switch off the ignition.
11. Operate the fuel lift pump again, repeating the operations described above until the engine starts.

If the engine starts, its operation may be unstable and noisy for the first few minutes, which is not a fault.

The above materials cover the removal, inspection and installation of the Cummins ISF3.8 engine fuel system components: replacement of the high-pressure fuel pump, disassembly and assembly of the pump, inspection and replacement of the fuel metering valve, checking the fuel return, removal and installation of the injectors, removal and installation of the fuel rail, checking the pressure relief valve, removal and installation of the fuel filter. The material is intended for diagnostics, fault-finding and repair of the fuel system.