This is the Isuzu 4JG2 Service Manual (publication 604-01-200K), a 219-page factory guide to the 4JG2 industrial diesel engine. It runs from general information and specifications through maintenance, three engine assembly sections covering disassembly, inspection and repair, and reassembly, and on to the individual system chapters.Separate sections cover the lubricating system, cooling system, fuel system and engine electricals, backed by a full troubleshooting chapter and a special tool list. You get the working numbers, including cold valve clearance of 0.40 mm, fuel injection timing at 6 degrees BTDC, low idle of 675 to 725 rpm and the main torque figures for the flywheel, connecting rods and cylinder head.For owners and mechanics servicing a 4JG2 in a forklift, genset or light truck, this PDF supplies the exact procedures and settings needed to maintain, diagnose and rebuild the engine.
What's Inside This Isuzu 4JG2 Manual
| System | Pages | Key Topics |
|---|---|---|
| Section 1. General Information | 4-21 | General repair instructions, Main data and specifications, Tightening torque specifications, Angular nut and bolt tightening method, Special parts fixing nuts and bolts |
| Section 2. Maintenance | 22-33 | Model identification, Injection pump identification, Lubricating system, Fuel system, Cooling system, Valve clearance adjustment |
| Section 3. Engine Assembly(1) | 34-51 | - |
| Section 4. Engine Assembly(2) | 52-87 | - |
| Section 5. Engine Assembly(3) | 88-115 | - |
| Section 6. Lubricating System | 116-127 | Main data and specifications, General description, Oil pump, Oil filter with built-in oil cooler |
| Section 7. Cooling System | 128-137 | Main data and specifications, General description, Water pump, Thermostat |
| Section 8. Fuel System | 138-149 | General description, Injection nozzle, Injection pump data |
| Section 9. Engine Electricals | 150-175 | Starter, Alternator |
| Section 10. Troubleshooting | 176-201 | Hard starting, Unstable idling, Insufficient power, Excessive fuel consumption, Excessive oil consumption, Overheating |
| Section 11. Special Tool List | 202-205 | Compression Gauge, Compression Gauge Adaptor, Valve Spring Compressor, Valve Guide Replacer, Cylinder Liner Installer, Camshaft Bearing Replacer |
| Section 12. Conversion Table | 206-219 | Length, Area, Volume, Mass, Pressure, Torque |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Level Sensor Torque | 1.3 (9/13) kg-m (lb.ft/N-m) | p. 21 |
| Oil Filter Bolt Torque | 1.4 - 2.4 (10 - 17/14 - 24) kg-m(lb.ft/N-m) | p. 112 |
| Starter Bolt Torque | 6.7 - 8.7 (48 - 63/60 - 85) kg-m(lb.ft/N-m) | p. 111 |
| Thermostat Initial Opening Temperature | 76.5 (170) °C(°F) | p. 24 |
| Injection pressure | 150 (2130/14.7) kg/cm² (psi/MPa) | p. 23 |
| Cylinder Head Bolt Torque (1st stop) | 4.5 - 5.5 (33 - 40/44 - 54) kg-m(lb.ft/N-m) | p. 107 |
| Fuel Injection Timing (B.T.D.C.) | 6 degrees | p. 6 |
| Valve Clearance (Cold, Intake & Exhaust) | 0.40 mm (0.016 in) | p. 6 |
| Low Idle Speed | 675 - 725 rpm | p. 6 |
| Lubricating Oil Volume | 7.5 L (1.98 US/gal) | p. 6 |
| Flywheel Bolt Torque | 113 - 123 N-m | p. 12 |
| Injection Nozzle Pressure | 150 kg/cm² (14.7 MPa) | p. 23 |
Isuzu 4JG2 Common Problems This Manual Covers
Hard starting on the 4JG2
Faulty fuel delivery, a weak battery or worn injection nozzles leave the 4JG2 cranking without firing. The troubleshooting section works through the likely causes across the fuel, electrical and compression paths.
Manual Section: Section 10. Troubleshooting p. 176Starter motor inoperative
A discharged battery, loose or rusted cables or a defective magnetic switch can leave the starter dead. The engine electricals section covers the starter and its data, and lists the correct starter bolt torque.
Manual Section: Section 9. Engine Electricals p. 150Unstable idling
Improper injection timing, a faulty thermostat or excessive fuel injection make the 4JG2 hunt at idle. The maintenance section covers injection pump identification and valve clearance adjustment to set it right.
Manual Section: Section 2. Maintenance p. 22Insufficient power under load
A clogged exhaust, a damaged cylinder head gasket, a loose fan belt or wrong injection timing rob the engine of power. The troubleshooting section isolates the cause step by step.
Manual Section: Section 10. Troubleshooting p. 176Overheating or slow warm-up
A faulty thermostat causes overheating or overcooling and long warm-up times. The cooling system section covers the water pump and thermostat, with the initial opening temperature of 76.5 degrees C (170 degrees F).
Manual Section: Section 7. Cooling System p. 128Fuel filter and injection nozzle wear
Clogged filters and worn injection nozzles cause rough running and poor delivery. The fuel system section covers the injection nozzle and injection pump data, with nozzle pressure at 150 kg/cm2 (14.7 MPa).
Manual Section: Section 8. Fuel System p. 138Frequently Asked Questions
Which engine does this manual cover?
It is the factory service manual for the Isuzu 4JG2 industrial diesel engine, published under Isuzu number 604-01-200K, covering the single 4JG2 model used in forklifts, gensets and light trucks.
Does it include torque specifications?
Yes. The General Information section carries the tightening torque specifications and the angular tightening method, including the flywheel bolt torque of 113 to 123 N-m for the 4JG2. p. 4
What are the valve clearance and idle settings?
The Maintenance section covers valve clearance adjustment, set at 0.40 mm (0.016 in) cold for intake and exhaust, with a low idle speed of 675 to 725 rpm. p. 22
Is a troubleshooting guide included?
Yes. The Troubleshooting section covers hard starting, unstable idling, insufficient power, excessive fuel and oil consumption and overheating, linking each symptom to the system to check. p. 176
How will I receive this Isuzu 4JG2 Service Manual?
Instant PDF download. The full 219-page searchable service manual is available immediately after payment. Open it on your laptop, tablet, or phone.
Are there any print restrictions on this Isuzu 4JG2 manual?
Yes, print as many copies as you need. No restrictions. Most mechanics print the relevant section and take it to the bench.
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