Isuzu 4HK1 Generator Set

⚠ Adjust valve clearance carefully so that the bridge may become level (hit the end of the 2 valve axes).

⚠ If the bridge adjusting screw is poorly adjusted, the bridge may tilt, be pushed down and seize, damaging the bridge guide.

Tools: 0.4 mm thickness gauge, flathead screwdriver

1. Loosen all bridge and rocker arm adjusting nuts and screws (4HK1: 8 nuts/8 screws, 6HK1: 12 nuts/12 screws).
2. Place a 0.4 mm thickness gauge between the No.1 cylinder rocker arm end and bridge cap.
3. Tighten rocker arm adjusting screw until the gauge is snug between rocker arm end and bridge cap.
4. Tighten the rocker arm lock nut.
5. Tighten the bridge adjusting screw until the bridge contacts the valve head.
6. Tighten the bridge lock nut.
7. Check the thickness gauge is still held snugly; if too tight loosen bridge screw and nut.
8. Remove the thickness gauge and repeat for remaining cylinders.

⚠ Adjust while cold.

⚠ Ensure bridge is level and hits both valve axis ends.

⚠ Avoid seizing bridge guide.

Tools: 0.4 mm thickness gauge, wrenches, screwdriver

1. Remove cylinder head cover and fuel injector harness ASM.
2. Remove leak off pipe and rotate crankshaft to No.1 cylinder compression TDC.
3. Insert 0.4 mm thickness gauge between rocker arm and bridge to check clearance.
4. Loosen all bridge and rocker arm adjusting nuts and screws (4HK1: 8 nuts/8 screws; 6HK1: 12 nuts/12 screws).
5. Place 0.4 mm thickness gauge between No.1 cylinder rocker arm end and bridge cap.
6. Tighten rocker arm adjusting screw until gauge is snug, then tighten lock nut.
7. Tighten bridge adjusting screw until bridge contacts valve head, then tighten lock nut.
8. Check gauge snugness; adjust if too tight.
9. Remove gauge and repeat for remaining cylinders.

⚠ Clear ECM memory after measurement because DTC is recorded when harness connector is removed.

Tools: Compression gauge 5-8840-2675-0 (J-26999-12), Compression gauge adapter EN-46722 (4HK1), Compression gauge adapter 5-8840-2622-0 (6HK1)

1. Warm up engine.
2. Remove negative battery terminal and all glow plugs.
3. Disconnect fuel injector harness connector (no fuel injected).
4. Install compression gauge adapter and gauge (4HK1: EN-46722; 6HK1: 5-8840-2622-0; gauge: 5-8840-2675-0/J-26999-12).
5. Turn starter and measure each cylinder; keep engine speed at 200 rpm or more.
6. Remove gauge, reconnect harness, install glow plugs, reconnect battery.

⚠ Adjust while being cold.

Tools: 0.4 mm thickness gauge

1. Remove the cylinder head cover.
2. Remove the fuel injector harness ASM by loosening the terminal nuts alternately.
3. Remove the leak off pipe.
4. Rotate the crankshaft so No.1 cylinder is at compression TDC.
5. Insert a 0.4 mm thickness gauge between rocker arm and bridge to check clearance.

⚠ Be careful not to damage the cylinder head.

⚠ Do not reuse the valve stem oil seal.

⚠ Do not reuse the removed injector sleeve.

Tools: SST: 5-8840-2621-0 - valve spring replacer, SST: 8-9439-6862-0 - pivot ASM, SST: 5-8840-2628-0 - valve guide replacer, SST: 5-8840-2623-0 - nozzle sleeve remover

1. Remove the front and rear engine hanger brackets from the cylinder head assembly.
2. Remove the inlet cover from the cylinder head assembly together with the EGR pipe D.
3. Remove the exhaust manifold bracket and the exhaust manifold from the cylinder head assembly.
4. Remove the water outlet pipe, then the thermostat and the gasket from the thermostat.
5. Remove the overheat switch from the cylinder head assembly.
6. Remove the engine coolant temperature sensor from the cylinder head assembly.
7. Remove the CMP sensor from the cylinder head assembly without subjecting the sensor to shock.
8. Tap and tilt the idle gear C cover, remove it with pliers, then remove idle gear C.
9. Press the valve spring with the special tool, remove the split collar, then the valve spring seat and valve spring.
10. Remove the inlet valve and exhaust valve, organizing them according to the cylinders.
11. Remove the valve stem oil seal with pliers (do not reuse) and the valve spring seat.
12. Remove the valve guide using the special tool, tapping out from the bottom surface of the cylinder head.
13. Heat the valve seat insert with the gas burner, cool naturally, then remove it using the driver.
14. Remove the injector sleeve using the special tool, tapping out from the bottom surface of the cylinder head.
15. Weld a nut to the bridge guide, remove it with the sliding hammer, then remove the oil seal.

⚠ Do not reuse the removed injection pipe.

⚠ Do not reuse the removed fuel pipe.

⚠ Seal the common rail and injector to prevent foreign material from entering.

1. Disconnect the battery ground cable from the battery.
2. Drain the coolant from the radiator; after discharge make sure to tighten the drain plug.
3. Disconnect the engine harness connectors from the engine assembly.
4. Remove the air cleaner duct, air intake hose, exhaust pipe, oil feed pipe, oil return pipe, water return pipe and water feed pipe from the turbocharger.
5. Remove the exhaust manifold stay from the cylinder block and the turbocharger assembly.
6. Disconnect the harness connector and remove the turbocharger assembly from the exhaust manifold.
7. Remove the box-shaped or cylindrical EGR cooler assembly: disconnect the water rubber hose and remove the EGR heat protector, EGR pipes and coolers.
8. Remove the EGR valve from the EGR pipe D.
9. Remove the EGR cooler water pipe from the engine assembly.
10. Remove the intake throttle valve from the inlet pipe and disconnect its harness connector.
11. Disconnect the boost sensor, boost temperature sensor, EGR valve and IMT sensor connectors, then remove the inlet pipe from the case.
12. Remove the oil level gauge from the guide tube and remove the guide tube from the cylinder block.
13. Remove the glow plug connector and the glow plug from the cylinder head assembly.
14. Remove the injection pipe from the injector and common rail; do not reuse the removed injection pipe.
15. Remove the fuel pipe, fuel leak-off pipe assembly and common rail assembly.

⚠ Push connector thoroughly until claws raise.

Tools: torque wrench

1. Install gasket on lower cover.
2. Install head cover case.
3. Install fuel injector harness connector; push until claws lock.
4. Install gasket on head cover.
5. Install head cover and tighten in order.

Tools: hand tools

1. Remove head cover.
2. Remove gasket.
3. Remove fuel injector harness connector.
4. Remove head cover case.
5. Remove gasket.

⚠ Be extremely careful not to damage the injector nozzle.

Tools: SST: 5-8840-2826-0 - injector remover, SST: 5-8840-0019-0 - sliding hammer

1. Remove the injector leak-off pipe from the injector.
2. Remove the injector from the cylinder head assembly; when difficult, use a special tool.
3. Confirm that the sleeve is not pulled out together with the injector.
4. Store each ID code plate on the injector head with the cylinder number tag attached.

⚠ Tighten bolt indicated with arrow.

⚠ Tighten stud part together with common rail.

⚠ Install within 7 minutes.

Tools: liquid gasket, torque wrench

1. Apply liquid gasket (ThreeBond 1207C or equivalent) bead diameter 2.5-5.5 mm along groove.
2. Install within 7 minutes after applying liquid gasket.
3. Install case ASM.
4. Install gasket on inlet pipe and tighten.
5. Install common rail.

⚠ Do not forget bolt inside inlet cover.

Tools: hand tools

1. Remove common rail.
2. Remove inlet pipe.
3. Remove case ASM.
4. Remove inlet cover (be careful of bolt inside).
5. Peel liquid gasket off carefully.

⚠ Do not over-tighten exhaust manifold to allow heat expansion.

Tools: torque wrench

1. Put gasket in and install exhaust manifold; tighten nuts/bolts in order (4HK1: 2 nuts/6 bolts; 6HK1: 12 nuts).
2. Install gasket and turbocharger to exhaust manifold; tighten nuts.
3. Tighten adapter bolts (exhaust manifold side).
4. Install water feed pipe to turbocharger (4HK1 only); tighten joint bolts.
5. Install pipe bracket and tighten bolts.