Isuzu NPR 4J Series

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4JB1/4JB1T/4JB1TC/4JG2 – ENGINE 6A1 – 77

Wiring Connector

• Disconnect the wiring connectors from the car speed

sensor, the neutral switch and the back-up light switch.

Shift Cable and Select Cable

• Disconnect the shift cable and select cable on the

transmission side.

Clutch Slave Cylinder

• Remove the clutch pipe fixing clips and the clip

bracket (Right hand drive models only).

• Remove the slave cylinder assembly with the flexible

hose attached, and then tie it to the frame so that it

does not interface with servicing work.

Exhaust Brake Assembly

Front Exhaust Pipe

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Main Page

Table of Contents4
Service Information Contents5
Table of Contents5
Troubleshooting Contents6
Hard Starting7
- Starter Inoperative7
- Starter Motor Operates but Engine Does Not Turn over7
- Engine Turns over but Does Not Start8
- Quick-On Start System9
Unstable Idling10
Insufficient Power11
Excessive Fuel Consumption13
Excessive Oil Consumption13
Overheating14
White Exhaust Smoke14
Dark Exhaust Smoke15
Oil Pressure Does Not Rise15
Abnormal Engine Noise16
- Engine Knocking16
- Gas Leakage Noise16
- Continuous Noise16
- Slapping Noise17
Engine Cooling Trouble18
Engine Electrical Part Trouble19
Engine Has Less than Normal Power24
Turbocharger24
- Blue or Black Smoke26
- Excessive Turbocharger Noise30
- Excessive Rotating Part Wear32
- 4JB1, 4JB1TC, 4JG2, Oil Filter and Oil Cooler33
Lubrication Chart33
Main Data and Specifications34
- Engine Cooling36
- Starting System36
- Charging System37
Engine Mechanical38
Service Standard38
- Model Identification42
- Air Cleaner42
- Dust Fouled Element42
Servicing42
- Lubricating System43
- Main Oil Filter (Cartridge Type Paper Element) Replacement Procedure43
- Fuel Filter Water Draining Procedure44
- Replacement Procedure44
Fuel System44
- Engine Coolant Change Procedure45
- Cooling System45
- Coolant Level45
- Air Bleeding45
- Cooling System Inspection47
- Radiator Cap Inspection47
- Thermostat Operating Test47
- Drive Belt Adjustment48
- Cooling Fan Pulley Drive Belt48
- Compressor Pulley Drive Belt48
- Power Steering Oil Pump Pulley Drive Belt48
- Engine Control49
- Idling Speed Inspection49
- Idling Speed Adjustment49
- Accelerator Control Cable Adjustment49
- Valve Clearance Adjustment50
- Injection Timing Adjustment51
- Quick-On Start System Inspection Procedure53
- Quick-On Start II System (4JB1 / 4JB1T / 4JB1TC Only)53
- Compression Pressure Measurement53
- Quick-On Start III System (4JG2 Only)54
- Cylinder Head Cover, Cylinder Head Rocker, Shaft Braker55
Fixing Torque55
- Crankshaft, Bearing Cap, Connecting Rod Bearing Cap, Crankshaft Damper Pulley, Flywheel, Oil Pan56
- Timing Pulley Housing, Timing Pulley, Timing Gear, Camshaft Oil Seal Retainer57
- Cooling System and Lubrication System58
- Intake Manifold, Exhaust Manifold, Exhaust Pipe59
- Engine Electricals61
- Engine Fuel62
- Engine Mounting Bracket63
Special Tools64
- General Engine Mechanical Contents68
- Cylinder Head69
  - Cylinder Head Disassembly69
  - Cylinder Head Clean70
  - Cylinder Head Inspection and Repair70
  - Hot Plug Depression (4JG2 Only)71
  - Combustion Chamber Inspection (4JG2 Only)72
  - Hot Plug Inspection72
  - Hot Plug Installation (4JG2 Only)72
  - Hot Plug Removal (4JG2 Only)72
  - Cylinder Head Reassembly73
  - Heat Shield Installation (4JG2 Only)73
  - Heat Shield Removal (4JG2 Only)73
- Valve Spring, Valve Guide Oil Seal, Valve Guide, Push Rod77
  - Valve Spring, Valve Guide Oil Seal, Valve Guide, Push Rod Disassembly77
  - Valve Guide78
  - Valve Spring78
  - Valve Spring, Valve Guide Oil Seal, Valve Guide, Push Rod Inspection and Repair78
  - Valve Guide Replacement80
  - Valve Thickness80
  - Valve Contact Width81
  - Valve Depression81
  - Valve Seat Insert Replacement81
  - Push Rod Curvature82
  - Valve Seat Insert Correction82
  - Valve Spring, Valve Guide Oil Seal, Valve Guide, Push Rod Reassembly83
- Camshaft, Tappet84
  - Camshaft, Tappet Disassembly84
  - Camshaft, Tappet Inspection and Repair85
  - Camshaft Bearing Replacement86
  - Tappet87
  - Tappet Reassembly87
- Rocker Arm Assembly91
  - Rocker Arm Disassembly91
  - Rocker Arm Inspection and Repair91
  - Rocker Arm Shaft Run-Out93
- Oil Pump94
  - Oil Pump Disassembly94
  - Oil Pump Inspection and Repair95
  - Oil Pump Reassembly96
- Crankshaft98
  - Crankshaft Disassembly98
  - Crankshaft Inspection and Repair99
  - Run-Out101
  - Crankshaft Bearing Selection102
  - Crankshaft Reassembly103
  - Timing Belt108
  - Crankshaft Damper Pulley110
  - Injection Pump112
- Piston and Connecting Rod114
  - Piston and Connecting Rod Disassembly114
  - Piston and Connecting Rod Inspection and Repair115
  - Piston and Piston Ring115
  - Piston and Connecting Rod Reassembly120
- Cylinder Block123
  - Cylinder Block Disassembly123
  - Cylinder Block Inspection and Repair124
  - Cylinder Liner Projection Inspection124
  - Flatness124
  - Cylinder Liner Bore Measurement125
  - Cylinder Liner Grade Selection125
  - Cylinder Body Bore Measurement126
  - Cylinder Liner Installation127
  - Cylinder Block Reassembly128
  - 4JB1/4JB1T/4JB1TC/4JG2-Engine Contents136
- General Description137
- Engine Mount (RH)139
  - Engine Mount (RH) Removal139
  - Engine Mount (RH) Installation140
- Engine Mount (LH)141
  - Engine Mount (LH) Removal141
  - Engine Mount (LH) Installation142
- Inlet Manifold143
  - Inlet Manifold Removal143
  - Inlet Manifold Installation144
- Exhaust Manifold145
  - Exhaust Manifold Removal145
  - Exhaust Manifold Installation146
- Oil Cooler147
  - Oil Cooler Removal147
  - Oil Cooler Inspection148
  - Oil Cooler Installation148
- Oil Filter Cartridge149
  - Oil Filter Cartridge Installation149
  - Oil Filter Cartridge Removal149
- Cylinder Head Cover150
  - Cylinder Head Cover Installation150
  - Cylinder Head Cover Removal150
- Rocker Arm Shaft Assembly152
  - Rocker Arm Shaft Installation152
  - Rocker Arm Shaft Removal152
- Valvestem Oil Controller and Valve Spring155
  - Valvestem Oil Controller and Valve Spring Removal155
  - Valvestem Oil Controller and Valve Spring Installation156
  - Timing Gear (4JB1, 4JB1TC, 4JG2 Gear Type)158
  - Timing Gear (4JB1, 4JB1TC, 4JG2 Gear Type) Removal158
  - Idler Gear "A" End Play Measurement159
  - Timing Gear Backlash Measurement159
  - Timing Gear (4JB1, 4JB1TC, 4JG2 Gear Type) Installation161
  - Timing Belt (4JG2 Belt Type)165
  - Timing Belt (4JG2 Belt Type) Removal165
  - Timing Belt (4JG2 Belt Type) Installation167
  - Cylinder Head and Gasket Removal172
- Cylinder Head Assembly and Gasket172
  - Cylinder Head and Gasket Installation176
  - Tension Adjustment181
- Oil Pan183
  - Oil Pan Removal183
  - Oil Pan Installation185
- Oil Pump Assembly186
  - Oil Pump Removal186
  - Oil Pump Installation188
- Piston, Piston Ring and Connecting Rod189
  - Piston, Piston Ring and Connecting Rod Removal189
  - Piston, Piston Ring and Connecting Rod Installation192
- Camshaft and Tappet198
  - Camshaft and Tappet Removal198
  - Camshaft and Tappet Installation203
- Crankshaft Front Oil Seal (Gear Drive Type)206
  - Crankshaft Front Oil Seal (Gear Drive Type) Removal206
  - Crankshaft Front Oil Seal (Gear Drive Type) Installation207
- Crankshaft Front Oil Seal (Belt Drive Type)208
  - Crankshaft Front Oil Seal (Belt Drive Type) Removal208
  - Crankshaft Front Oil Seal (Belt Drive Type) Installation209
- Crankshaft Rear Oil Seal (Gear & Belt Drive Type)211
  - Crankshaft Rear Oil Seal (Gear & Belt Drive Type) Removal211
  - Crankshaft Rear Oil Seal (Gear & Belt Drive Type) Installation215
- Flywheel and Pilot Bearing218
  - Flywheel and Pilot Bearing Removal218
  - Flywheel and Pilot Bearing Installation219
- Crankshaft and Main Bearings220
  - Crankshaft and Main Bearings Removal221
  - Crankshaft and Main Bearings Installation225
- Engine Assembly231
  - Engine Removal231
  - Engine Installation238
  - Engine Cooling Contents244
  - Engine Cooling General Description244
  - Radiator245
  - Thermostat245
  - Water Pump245
  - Anti-Freeze Solution248
- On-Vehicle Service249
  - Water Pump Removal249
  - Water Pump Inspection250
  - Water Pump Installation251
  - Thermostat Inspection253
  - Thermostat Removal253
  - Thermostat Installation254
  - Radiator Removal255
  - Radiator Inspection256
  - Radiator Installation257
  - Drive Belt Adjustment Inspection258
  - Engine Fuel Contents260
- General Description261
  - Fuel Flow262
  - Injection Pump263
  - Fuel Filter and Water Separator264
  - Injection Nozzle265
- Fuel Filter Assembly266
  - Fuel Filter Installation266
  - Fuel Filter Removal266
- On-Vehicle Service266
- Fuel Filter Cartrige267
  - Fuel Filter Cartrige Installation267
  - Injection Nozzle Inspection268
  - Injection Nozzle Removal268
  - Injection Nozzle Disassembly (4JG2 Engine)269
  - Injection Nozzle Inspection (4JG2 Engine)269
  - Injection Nozzle Reassembly (4JG2 Engine)270
  - Adjustment of Injection Opening Pressure (4JG2 Engine)271
  - Oil Tight Test (4JG2 Engine)271
  - Injection Nozzle Installation (4JG2 Engine)272
  - Injection Nozzle (Two Spring Nozzle Holder) (4JB1-TC Only)273
  - Injection Nozzle Disassembly273
  - Only)274
  - Reassembly and Adjustment Procedure274
  - Reassembly and Opening Pressure Adjustment (4JB1-TC274
  - Injection Nozzle Disassembly (4JBI/4JB1T Engine)282
  - Injection Nozzle Inspection and Repair (4JB1/4JB1 T Engine)282
  - Injection Nozzle Installation (4JB1/4JB1 T Engine)284
  - Injection Pump Asm (4JB1/4JB1T, 4JG2 Gear Drive Type)285
  - Injection Pump Asm (4JB1/4JB1T, 4JG2 Gear Drive Type) Removal285
- Injection Pump Assembly (Gear Drive Type)286
- Injection Pump Asm (4JB1/4JB1T, 4JG2 Gear Drive Type) Installation287
- Injection Pump Assembly (Belt Drive Type)287
  - Injection Pump Assembly (4JG2 Belt Drive Type)290
  - Injection Pump Assembly (4JG2 Belt Drive Type) Removal290
  - Injection Pump Assembly (4JG2 Belt Drive Type) Installation294
- Injection Timing Adjustment300
- Adjustment of Idling Speed301
- Injection Pump Data302
  - Test Conditions302
  - Identification Plate and Number303
- Injection Volume and Governor Performance Diagram304
- Fuel Tank314
  - Fuel Tank Removal314
  - Fuel Tank Installation315
- Fuel Gauge Unit316
  - Fuel Gauge Unit Installation316
  - Fuel Gauge Unit Removal316
- Accelerator Control Cable317
  - Accelerator Control Removal317
  - Accelerator Control Inspection318
  - Accelerator Control Installation318
- Accelerator Pedal319
  - Accelerator Pedal Installation319
  - Accelerator Pedal Removal319
- Idling Control Cable321
  - Idling Control Cable Installation321
  - Idling Control Cable Removal321
- Air Cleaner Element323
  - Air Cleaner Element Removal323
  - Air Cleaner Element Installation324
  - Battery Contents326
  - Engine Electrical Contents326
- Battery327
- Diagnosis327
- Fluid Level Check327
- General Description327
  - Visual Inspection327
  - Voltage Check327
  - Load Test328
- Battery Charging329
- On-Vehicle Service329
- Jump Starting330
  - Jump Starting with an Auxiliary (Booster) Battery330
  - Jump Starting Procedure331
- Main Data and Specifications332
- Removal and Installation of Battery332
  - Starting Circuit334
  - Starting System Contents334
  - Starting System Installation336
  - Starting System Removal336
  - Starting System Disassembly338
  - Unit Repair338
  - Armature341
  - Starting System Inspection and Repair341
  - Yoke342
  - Bearing343
  - Brush and Brush Holder343
  - Overrunning Clutch343
  - Starting System Reassembly344
  - Magnetic Switch345
  - Charging System Contents346
  - Generator347
  - Charging Circuit348
  - General On-Vehicle Inspection349
  - Generator Removal350
  - Generator Installation351
  - Generator Disassembly354
  - Generator Inspection and Repair355
  - Rotor356
  - Stator Coil356
  - Brush357
  - Diode357
  - IC Regulator358
  - Vacuum Pump359
  - Generator Reassembly360
  - Charging System Disassembly362
  - Charging System Inspection and Repair364
  - Charging System Reassembly366
  - Output Characteristic366
  - QOSII Preheating System (4JB1/4JB1T/4JB1TC Only)368
  - QOS II Timing Chart369
  - System Diagram369
  - Gow Plug370
  - Inspection on QOSII System Operation Thermo Switch370
  - QOSII System Troubleshooting371
  - QOSIII Preheating System (4JG2 Only) Contents374
  - QOS III Flow Chart376
  - QOS III Block Chart377
  - Inspection on QOSIII System Operation378
  - Glow Plug379
  - Thermo Sensor379
  - Charge Relay380
  - Dropping Resistor380
  - Glow Plug Relay380
  - Exhaust Gas Recirculation (EGR) System Contents382
- General Description383
- EGR System Operation384
- EGR System Wiring Diagram384
  - Exhaust Gas Recirculation (EGR) System Check385
  - EGR System Inspection386
  - Engine Exhaust Contents388
- General Description389
  - General Export389
  - Model ’91/542B (Euro 2)389
- Three Way Catalytic Converter390
- Front Exhaust Pipe391
- Front Exhaust Pipe Removal391
- On-Vehicle Service391
  - Exhaust Brake Unit Inspection392
  - Front Exhaust Pipe Installation392
  - Turbocharger Contents394
  - Turbocharger Main Data and Specifications395
- General Description396
- Identification of Unit397
- Precautions397
- Turbocharger Servicing397
  - Disassembly Steps398
  - Turbocharger Disassembly398
  - Turbocharger Inspection and Repair400
  - Reassembly Steps402
  - Turbocharger Reassembly402
- Ihi Service Network404

Isuzu NPR 4J Series - Page 212

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