Name: Isuzu A-4JA1
Brand: Isuzu
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TROUBLESHOOTING

183

2. UNSTABLE IDLING

Checkpoint Trouble Cause Countermeasure

Valve clearance

Compression pressure

Valve clearance improperly

adjusted

Adjust the valve clearance

Blown out cylinder head gasket

Worn cylinder liner

Piston ring sticking or broken

Improper seating between the

valve and the valve seat

Replace the related parts

NG NG

Continued from the previous page

Table of Contents3
General Information4
General Repair Instructions5
Notes on the Format of this Manual5
General Information7
Main Data and Specifications9
Standard Bolt10
Tightening Torque Specifications10
- Tightening Torque Specifications11
- Flanged Head Bolt11
- Special Parts Fixing Nuts and Bolts12
- Cylinder Head Cover, Cylinder Head, and Rocker Arm Shaft Bracket12
- Timing Gear Case, Flywheel Housing, Camshaft, and Timing Gear14
- Cooling and Lubricating System15
- Intake and Exhaust Manifold16
- Engine Electrical17
- Fuel Injection System18
Maintenance20
- Engine Serial Number21
- Injection Pump Identification21
- Lubricating System21
- Main Oil Filter21
- Model Identification21
- Fuel Filter22
- Fuel System22
- Cooling System25
  - Operating Test25
  - Thermostat25
- Valve Clearance Adjustment26
- In-Line Type Injection Pump27
- Injection Timing27
- Compression Pressure Measurement29
  - Engine Oil Viscosity Chart30
  - Engine Oil Viscosity Grade – Ambient Temperature30
- Recommended Lubricants30
- Engine Repair Kit31
Section 3. Engine Assembly (1)32
Engine Assembly (1)32
Disassembly34
- Fuel Injection Pipe with Clip35
- Injection Pump35
- Exhaust Manifold35
- Injection Nozzle Holder38
- Rocker Arm Shaft and Rocker Arm38
- Cylinder Head38
- Crankshaft Damper Pulley with Dust Seal39
- Idler Gear39
- Timing Gear Backlash Measurement39
- Idler Gear “A” End Play Measurement39
- Piston and Connecting Rod with Upper Bearing40
- Connecting Rod Cap with Lower Bearing40
- Camshaft with Camshaft Timing Gear and Thrust Plate40
- Flywheel40
- Crankshaft Bearing Cap with Lower Bearing41
- Crankshaft Upper Bearing41
- Tappet41
- Crankshaft Rear Oil Seal41
- Single Unit42
- Rocker Arm Shaft Bracket43
- Rocker Arm Shaft Snap Ring43
- Split Collar45
- Intake and Exhaust Valve45
- Piston and Connecting Rod46
- Connecting Rod Bearing47
- Piston Ring47
- Piston Pin Snap Ring47
- Piston Pin47
- Camshaft, Camshaft Timing Gear, and Thrust Plate48
- Camshaft Timing Gear49
- Thrust Plate49
Engine Assembly (2)50
- Cylinder Head Lower Face Warpage51
- Exhaust Manifold Fitting Face Warpage51
- Cylinder Head Height (Reference)51
Inspection and Repair51
- Valve Guide52
- Manifold Fitting Face Warpage52
- Valve Stem and Valve Guide Clearance52
- Valve Guide Replacement52
- Valve and Valve Seat Insert53
- Valve Guide Installation53
- Valve Stem Outside Diameter53
- Valve Thickness53
- Valve Seat Insert Removal54
- Valve Seat Insert Replacement54
- Valve Depression54
- Valve Contact Width54
- Valve Seat Insert Installation55
- Valve Seat Insert Correction55
- Valve Spring56
- Valve Spring Free Height56
- Valve Spring Inclination56
- Valve Spring Tension56
- Rocker Arm Shaft and Rocker Arm Clearance57
- Rocker Arm Shaft Run-Out57
- Rocker Arm Shaft Outside Diameter57
- Rocker Arm Correction58
- Cylinder Body58
- Cylinder Body Upper Face Warpage58
- Cylinder Liner Bore Measurement59
- Cylinder Liner Projection Inspection59
- Cylinder Body Bore Measurement60
- Cylinder Liner Removal60
- Cylinder Liner Grade Selection60
- Cylinder Liner Replacement60
- Cylinder Liner Installation61
- Piston Selection62
- Piston Grade Selection63
- Piston Grade63
- Cylinder Liner and Piston Clearance63
- Tappet and Push Rod64
- Tappet Outside Diameter64
- Push Rod Curvature65
- Tappet and Cylinder Body Clearance65
- Camshaft65
- Camshaft Journal Diameter65
- Camshaft and Camshaft Bearing66
- Camshaft Bearing Replacement66
- Camshaft Run-Out66
- Cam Height66
- Camshaft Bearing Installation67
- Camshaft End Play67
- Thrust Plate Replacement67
- Thrust Plate Removal67
- Crankshaft and Bearing68
- Crankshaft Tufftriding Inspection68
- Judgment68
- Crankshaft Journal and Crankpin Diameter69
- Crankshaft Run-Out69
- Bearing Tension69
- Crankshaft Journal and Bearing Clearance70
- Connecting Rod Bearing Inside Diameter70
- Crankpin and Bearing Clearance71
- Crankshaft Timing Gear Replacement73
- Crankshaft Timing Gear Removal73
- Crankshaft Timing Gear Installation73
- Crankshaft Pilot Bearing Installation74
- Crankshaft Pilot Bearing Replacement74
- Crankshaft Pilot Bearing74
- Flywheel and Ring Gear75
- Ring Gear75
- Ring Gear Installation76
- Piston76
- Piston Ring Gap76
- Piston Ring and Piston Ring Groove Clearance77
- Piston Ring and Piston Ring Groove77
- Piston Pin Diameter78
- Piston Pin and Piston Clearance78
- Connecting Rod Bushing Removal78
- Connecting Rod Bushing Installation79
- Connecting Rod Alignment79
- Idler Gear Shaft and Idler Gear80
- Connecting Rod Side Face Clearance80
- Idler Gear Shaft Outside Diameter80
- Crankshaft Front Oil Seal Replacement81
- Idler Gear “A” Inside Diameter81
- Timing Gear Case Cover81
- Oil Seal Installation82
Engine Assembly (3)84
Reassembly85
- Rocker Arm Shaft86
- Valve Stem Oil Seal88
- Crankcase100
- Oil Pump with Oil Pipe101
- Flywheel Housing101
- Flywheel Housing Bolt Torque101
- Oil Pan102
- Intake Manifold108
Lubricating System112
- Item113
- Main Data and Specifications113
- General Description114
- Lubricating Oil Flow114
- Oil Pump117
- Vane and Pump Body Clearance118
- Oil Filter with Built-In Oil Cooler120
- Rotor and Vane Clearance118
- Vane, Rotor, and Cover Clearance118
- Relief Valve121
- Oil Cooler121
- Relief Vale123
Cooling System124
- Item125
- Main Data and Specifications125
- Coolant Flow126
- General Description126
- Water Pump127
- Water Pump128
- Thermostat134
Fuel System136
- Item137
- Main Data and Specifications137
- General Description138
- Fuel Filter and Water Separator140
- Injection Nozzle141
- Injection Pump Data146
- Injection Volume Adjustment146
- Governor Adjustment147
- Injection Quantity147
- Full Adjustment147
- Speed Lever Angle148
- Section 9. Engine Electricals150
Engine Electricals150
- Starter Identification151
- Armature157
- Armature Short Circuit Test157
- Armature Winding Ground Test157
- Armature Winding Continuity Test157
- Commutator Run-Out Test158
- Commutator Outside Diameter Measurement158
- Commutator Outside Diameter158
- Segment Mica Depth Measurement158
- Field Winding Continuity Test159
- Brush and Brush Holder159
- Field Winding Ground Test159
- Yoke159
- Brush Spring Inspection160
- Brush Holder Insulation Test160
- Pinion Clutch160
- Pinion Inspection160
- Pinion163
- Dust Cover163
- Shift Lever163
- Torsion Spring163
- Through Bolt164
- Lead Wire164
- Inspection after Reassembly164
- When Pinion Gap Deviates from Specified Value164
- Alternator165
- Alternator Identification165
- Rectifier with Brush Holder169
- Rotor and Bearing169
- Front Cover169
- Pulley and Fan169
- Ball Bearing170
- Rotor Coil Continuity Test171
- Rotor Coil Ground Test171
- Stator Coil Continuity Test171
- Stator Coil Ground Test172
- Rectifier (Positive Diode) Continuity Test172
- Rectifier (Negative Diode) Continuity Test173
- Rectifier Assembly Replacement Procedure173
- Brush174
Section 10. Troubleshooting178
- Hard Starting180
- Unstable Idling184
- Unstable Idling186
- Insufficient Power187
- Excessive Fuel Consumption191
- Excessive Oil Consumption193
- Overheating194
- White Exhaust Smoke196
- Dark Exhaust Smoke197
- Oil Pressure Does Not Rise198
- Abnormal Engine Noise200
- Engine Knocking200
- Continuous Noise201
- Gas Leakage Noise201
- Slapping Noise202
Section 11. Special Tool List204
- Special Tool List205
- General Rules208
Section 12. Repair Standards208
- Millimeters to Inches222
- Inches to Millimeters222
Section 13. Conversion Table222
- Feet to Meters223
- Length223
  - Meters to Feet223
  - Miles to Kilometers223
- Area224
- Volume224
- Mass226
- Pressure227
- Torque228
- Temperature229
- Fahrenheit to Centigrade229
- Centigrade to Fahrenheit229

Isuzu A-4JA1 User Manual

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Isuzu A-4JA1 Specifications

Related product manuals

Brand	Isuzu
Model	A-4JA1
Category	Engine
Language	English