Isuzu A-4JA1 Instruction manual

INDUSTRIAL
DIESEL ENGINE
A-4JA1, A-4JB1
MODELS
©2003 ISUZU MOTORS LIMITED
WORKSHOP MANUAL

FOREWORD
This Workshop Manual is designed to help you perform necessary
maintenance, service, and repair procedures on applicable Isuzu
industrial engines.
Information contained in this Workshop Manual is the latest
available at the time of publication.
Isuzu reserves the right to make changes at any time without prior
notice.
This Workshop Manual is applicable to 1998 and later models.
NOTICE
Before using this Workshop Manual to assist you in
performing engine service and maintenance operations,
it is recommended that you carefully read and throughly
understand the information contained in Section - 1
under the headings “General Repair Instruction” and
“Notes on The Format of This Manual”

TABLE OF CONTENTS
SECTION 1. GENERAL INFORMATION.................................. 1
SECTION 2. MAINTENANCE ............................................. 17
SECTION 3. ENGINE ASSEMBLY (1) .................................... 29
(DISASSEMBLY)
SECTION 4. ENGINE ASSEMBLY (2) .................................... 47
(INSPECTION AND REPAIR)
SECTION 5. ENGINE ASSEMBLY (3) .................................... 81
(REASSEMBLY)
SECTION 6. LUBRICATING SYSTEM.................................... 109
SECTION 7. COOLING SYSTEM ......................................... 121
SECTION 8. FUEL SYSTEM............................................... 133
SECTION 9. ENGINE ELECTRICALS ..................................... 147
SECTION 10. TROUBLESHOOTING....................................... 175
SECTION 11. SPECIAL TOOL LIST ........................................ 201
SECTION 12. REPAIR STANDARDS ....................................... 205
SECTION 13. CONVERSION TABLE....................................... 219

GENERAL INFORMATION
1
SECTION 1
GENERAL INFORMATION
TABLE OF CONTENTS
ITEM PAGE
General repair instructions ....................................................... 2
Notes on the format of this manual................................................. 2
Main data and specifications....................................................... 6
Tightening torque specifications ................................................... 7

GENERAL INFORMATION
GENERAL REPAIR INSTRUCTIONS
1. Before performing any service operation with the engine mounted, disconnect the grounding cable
from the battery.
This will reduce the chance of cable damage and burning due to short circuiting.
2. Always use the proper tool or tools for the job at hand.
Where specified, use the specially designed tool or tools.
3. Use genuine ISUZU parts.
4. Never reuse cotter pins, gaskets, O-rings, lock washers, and self locking nuts. Discard them as you
remove them. Replace them with new ones.
5. Always keep disassembled parts neatly in groups. This will ensure a smooth reassembly operation.
It is especially important to keep fastening parts separate. These parts vary in hardness and design,
depending on their installation position.
6. All parts should be carefully cleaned before inspection or reassembly.
Oil ports and other openings should be cleaned with compressed air to make sure that they are
completely free of obstructions.
7. Rotating and sliding part surfaces should be lubricated with oil or grease before reassembly.
8. If necessary, use a sealer on gaskets to prevent leakage.
9. Nut and bolt torque specifications should be carefully followed.
10. Always release the air pressure from any machine-mounted air tank(s) before dismounting the engine
or disconnecting pipes and hoses. To not do so is extremely dangerous.
11. Always check and recheck your work. No service operation is complete until you have done this.
NOTES ON THE FORMAT OF THIS MANUAL
This Workshop Manual is applicable to ISUZU industrial engine or engines which is or are stated in the
title.
When more than two engine models are dealt in the manual, such engines have common parts and
components as well as data and specifications, unless otherwise specified.
1. Find the applicable section by referring to the Table of Contents at the beginning of the Manual.
2. Common technical data such as general maintenance items, service specifications, and tightening
torques are included in the "General Information" section.
The section ENGINE ASSEMBLY is an exception. This parts are divided in three sections to facilitates
indexing.
3. Each section is divided into sub-sections dealing with disassembly, inspection and repair, and
reassembly.
2

GENERAL INFORMATION
3
4. When the same servicing operation is applicable to several different units, the manual will direct you
to the appropriate page.
5. For the sake of brevity, self-explanatory removal and installation procedures are omitted.
More complex procedures are covered in detail.
6. Each service operation section in this Workshop Manual begins with an exploded view of the
applicable area. A brief explanation of the notation used follows.
15
14
16 17
11
12
13
39
10
5
4
8
7
6
2
1
★
★Repair kit
★
★
★
★
★
Disassembly Steps - 2
1. Water by-pass hose
2. Thermostat housing
3. Water pump
▲4. Injection nozzle holder
5. Glow plug and glow plug connector
6. Cylinder head cover
▲7. Rocker arm shaft and rocker arm
8. Push rod
▲9. Cylinder head
10. Cylinder head gasket
▲11. Crankshaft damper pulley with
dust seal
12. Timing gear case cover
13. Timing gear cover
14. Timing gear oil pipe
15. Idler gear “B” and shaft
▲16. Idler gear “A”
17. Idler gear shaft
Inverted Engine
Parts marked with an asterisk (*) are
included in the repair kit.
Parts within a square frame are to be
removed and installed as a single unit,
and their disassembly steps or reas-
sembly steps are shown in the
illustrations respectively.
The number tells you the service oper-
ation sequence.
Removal of unnumbered parts is unne-
cessary unless replacement is required.
The "* Repair Kit" indicates that a repair
kit is available.
The parts listed under "Disassembly
Steps" or "Reassembly Steps" are in the
service operation sequence.
The removal or installation of parts
marked with a triangle (▲) is an
important operation. Detailed infor-
mation is given in the text.

GENERAL INFORMATION
4
8. The following symbols appear throughout this Workshop Manual. They tell you the type of service
operation or step to perform.
.... Removal .... Adjustment
.... Installation .... Cleaning
.... Disassembly ... Important operation requiring extra care
.... Reassembly .... Specified torque (tighten)
.... Alignment (marks) .... Special tool use required or
recommended(Isuzu tool or tools)
.... Directional indication .... Commercially available tool use
required or recommended
.... Inspection .... Lubrication (oil)
.... Measurement .... Lubrication (grease)
.... Sealant application
7. Below is a sample of the text of the Workshop Manual.
4. Camshaft Timing Gear
1) Install the thrust plate 1.
2) Apply engine oil to the bolt threads 2.
3) Install the camshaft timing gear with the timing
mark stamped side facing out.
Camshaft Timing Gear Bolt Torque kgf·m(lb.ft/N·m)
11.0 ± 1.0 (79.5 ± 7.2/107.8 ± 9.8)
1
2
13. Crankshaft Rear Oil Seal
1) Apply engine oil to the oil seal lip circumference
and the oil seal outer circumference.
2) Use the oil seal installer to install the oil seal to
the cylinder body.
Oil Seal Installer: 5-8840-0141-0
14. Flywheel Housing
1) Apply liquid gasket to the shaded area shown in
the illustration.
2) Tighten the flywheel housing bolts to the speci-
fied torque a little at a time in the sequence
shown in the illustration.
Flywheel Housing Bolt Torque kgf·m(lb.ft/N·m)
M10x1.25 (0.40x0.05) Bolt 5.6±1.0 (40.5±7.2/ 54.9±9.8)
M12x1.25 (0.47x0.05) Bolt 10.5±1.0 (76.0±7.2/103.0±9.8)
M12x1.75 (0.47x0.07) Bolt 9.8±1.0 (71.0±7.2/ 96.0±9.8)
7
4
8610 9
3
2
1
5
This is the item shown in the illus-
tration. It is marked with a triangle
(▲) on the Major Components page.
Letters and numbers contained in a
circle refer to the illustration.
Special tools are identified by the
tool name and/or number.
The illustration shows how the spe-
cial tool is to be used.
Symbols indicate the type of service
operation or step to be performed. A
detailed explanation of these
symbols follows.
Service data and specifications are
given in this table.

GENERAL INFORMATION
9. Measurement criteria are defined by the terms "standard" and "limit".
A measurement falling within the "standard" range indicates that the applicable part or parts are
serviceable.
"Limit" should be thought of as an absolute value.
A measurement which is outside the "limit" indicates that the applicable part or parts must be either
repaired or replaced.
10. Components and parts are listed in the singular form throughout the Manual.
11. Directions used in this Manual are as follows:
Front
The cooling fan side of the engine viewed from the flywheel.
Right
The right hand side viewed from the same position.
Left
The left hand side viewed from the same position.
Rear
The flywheel side of the engine.
Cylinder numbers are counted from the front of the engine.
The front most cylinder is No. 1 and rear most cylinder is the final cylinder number of the engine.
The engine's direction of rotation is counterclockwise viewed from the flywheel.
5

GENERAL INFORMATION
MAIN DATA AND SPECIFICATIONS
6
Engine Model A-4JA1 A-4JB1 4JB1T
Item
Engine type Water cooled, four-cycle, in-line, overhead valve
Combustion chamber type Direct injection
Cylinder liner type Dry
No. of cylinders - Bore x Stroke mm(in.) 4 - 93.0 x 92.0 4 - 93.0 x 102.0 4 - 93.0 x 102.0
(3.66 x 3.62) (3.66 x 4.02) (3.66 x 4.02)
Total piston displacement lit(cid) 2.449 (152.4) 2.771 (169.0) 2.771 (169.0)
Compression ratio (To 1) 18.4 18.2 18.2
*Engine dimensions mm(in.) 805 x 625 x 729 739 x 625 x 746 578 x 771 x 577
Length x Width x Height (31.7 x 24.6 x 28.7) (29.1 x 24.6 x 29.4) (22.8 x 30.4 x 22.7)
*Engine weight (Dry) kg(lb.) 218 (480) 220 (486) 245 (540)
Fuel injection order 1 –3–4 –2
*Fuel injection timing (B.T.D.C.) degrees 14
Specified fuel Diesel fuel
Injection pump In-line plunger, Bosch A type Bosch distributor
VE type
Governor Variable speed mechanical type
*Low idle speed rpm 850 –1,000
Injection nozzle Multi-hole type
Injection starting pressure kgf/cm2(psi/MPa) 185 (2630/18.1)
Fuel filter type Cartridge papaer element
Water sedimentor (if so equipped) Sediment/water level indicating type
Compression pressure kgf/cm2(psi/MPa) 31 (441/3.04)
Valve clearance (at cold) Intake mm(in.) 0.40 (0.0157)
Exhaust mm(in.) 0.40 (0.0157)
Lubrication method Pressurized circulation
Oil pump Trochoid type
Main oil filter type Cartridge paper element, full flow
Partial oil filter Not equipped
*Lubricating oil volume lit.(qts) 5.5 (5.8) –6.6 (7.0) 4.6 (4.9) –6.4 (6.8) 4.6 (4.9) –6.3 (6.7)
Oil cooler (if so equipped) Water cooled built in oil filter
Cooling method Pressurized forced circulation
Coolant volume lit.(qts) 5.0 (5.3)
Water pump Belt driven impeller type
Thermostat type Wax pellet type
*Alternator V-A 12 –35
*Starter V-kW 12 –2.2
Specifications marked with an asterisk (*) will vary according to engine application.

GENERAL INFORMATION
7
TIGHTENING TORQUE SPECIFICATIONS
The tightening torque values given in the table below are applicable to the bolts unless otherwise
specified.
STANDARD BOLT kgf·m (lb.ft/N·m)
An asterisk (*) indicates that the bolts are used for female threaded parts that are made of soft materials
such as casting. Those shown in parentheses in the strength class indicate the classification by the old
standard.
M 6 × 1.0
M 8 × 1.25
M10 × 1.25
M12 × 1.25
M14 × 1.5
M16 × 1.5
M18 × 1.5
M20 × 1.5
M22 × 1.5
M24 × 2.0
*M10 × 1.5
*M12 × 1.5
*M14 × 2.0
*M16 × 2.0
0.4 –0.8
(2.9 –5.8/3.9 –7.8)
0.8 –1.8
(5.8
– 13.0/7.8 – 17.7)
2.1 –3.5
(15.2 – 25.3/20.6 – 34.3)
5.0
– 7.5
(36.2
– 54.2/49.0 – 73.6)
7.8
– 11.7
(56.4
– 84.6/78.5 – 114.7)
10.6
– 16.0
(76.7
– 115.7/103.0 – 156.9)
15.4
– 23.0
(111.1
– 166.4/151.0 – 225.6)
21.0
– 31.6
(151.9
– 228.6/205.9 – 307.9)
25.6
– 42.2
(185.2
– 305.2/251.1 – 413.8)
36.6
– 55.0
(264.7
– 397.8/358.9 – 539.4)
2.0
– 3.4
(14.5
– 24.6/19.6 – 32.4)
4.6
– 7.0
(33.3
– 50.6/45.1 – 68.7)
7.3
– 10.9
(52.8
– 78.8/71.6 – 106.9)
10.2
– 15.2
(73.8
– 110.0/100.0 – 149.1)
0.5
– 1.0
(3.6
– 7.2/4.9 – 9.8)
1.2
– 2.3
(8.7
– 16.6/11.8 – 22.6)
2.8
– 4.7
(20.3
– 34.0/27.5 – 46.1)
6.2
– 9.3
(44.8
– 67.3/60.8 – 91.2)
9.5
– 14.2
(68.7
– 102.7/93.2 – 139.3)
13.8
– 20.8
(99.8
– 150.4/135.3 – 204.0)
19.9
– 29.9
(143.9
– 216.3/195.2 – 391.3)
27.5
– 41.3
(198.9
– 298.7/269.7 – 405.0)
37.0
– 55.5
(267.6
– 401.4/362.9 – 544.3)
43.9
– 72.5
(317.5
– 523.9/430.5 – 711.0)
2.8
– 4.6
(20.3
– 33.3/27.5 – 45.1)
5.8
– 8.6
(42.0
– 62.2/56.9 – 84.3)
9.0
– 13.4
(65.1
– 96.9/88.3 – 131.4)
13.2
– 19.8
(95.5
– 143.2/129.5 –194.2)
1.7
– 3.1
(12.3
– 22.4/16.7 – 30.4)
3.8
– 6.4
(27.5
– 46.3/37.3 – 62.8)
7.7
– 11.6
(55.7
– 83.9/75.5 – 113.8)
11.6
– 17.4
(83.9
– 125.6/113.8 – 170.6)
16.3
– 24.5
(118.9
– 177.2/159.9 – 240.3)
23.4
– 35.2
(169.3
– 254.6/229.5 – 345.2)
32.3
– 48.5
(233.6
– 350.8/316.8 – 475.6)
43.3
– 64.9
(313.2
– 469.4/424.6 – 636.5)
56.5
– 84.7
(408.7
– 612.6/554.1 – 830.6)
3.7
– 6.1
(26.8
– 44.1/36.3 – 59.8)
7.3
– 10.9
(52.8
– 78.8/71.6 – 106.9)
10.9
– 16.3
(78.8
– 118.9/106.9 – 159.9)
15.6
– 23.4
(112.8
– 169.3/162.8 – 229.5)
Refined
No mark
Non-Refined
4.8 (4T) 8.8(7T) 9.8 (9T)
Strength
Class
Bolt
Identification
Bolt
Diameter ×
pitch (mm)

GENERAL INFORMATION
8
TIGHTENING TORQUE SPECIFICATIONS
The tightening torque values given in the table below are applicable to the bolts unless otherwise
specified.
FLANGED HEAD BOLT kgf·m (lb.ft/N·m)
M 6 ×10.5
– 0.9 0.6 –1.2
(3.61 – 6.50/4.6
– 8.5 (4.33 –8.67/5.88 –11.76)
M 8 ×1.25 1.1
– 2.0 1.4
– 2.9 1.9 – 3.4
(7.95
–
14.46/10.78 – 19.61) (4.33 – 8.67/5.88 – 11.76) (13.74 – 24.59/18.63 – 33.34)
M10 ×1.25 2.3
– 3.9 3.6 – 6.4 4.3 – 7.2
(17.35 – 28.20/23.53 – 38.24) (26.03 – 44.12/35.30 – 59.82) (31.10 – 52.07/42.16 – 70.60)
*M10 ×1.5 2.3
– 3.8 3.5 – 5.8 4.1 – 6.8
(16.63
– 27.48/22.55 – 37.26) (25.31 – 41.95/34.32 – 56.87) (29.65 – 49.18/40.20 – 66.68)
M12 ×1.25 5.6
– 8.4 7.9 – 11.9 8.7 – 13.0
(40.50
– 60.75/54.91 – 82.37) (57.14 – 86.07/77.47 – 116.69) (62.92 – 94.02/85.31 – 127.48)
*M12 ×1.75 3.5
– 9.5 7.3 – 10.9 8.1 – 12.2
(37.61 – 56.41/50.99 – 76.49) (52.80 – 78.83/71.58 – 106.89) (58.58 – 88.24/79.43 – 119.64)
M14 ×1.5 8.5
– 12.7 11.7 – 17.6 12.6 – 18.9
(61.48
– 91.85/83.35 – 124.54) (84.62 – 127.30/114.73 – 172.59) (91.13 – 136.70/123.56 – 185.34)
*M14 ×27.6
– 11.5 11.1 – 16.6 11.8 – 17.7
(57.14
– 85.34/77.47 – 115.71) (80.28 – 120.06/108.85 – 162.79) (85.34 – 128.02/115.71 – 173.57)
M16 ×1.5 11.8
– 17.7 17.1
– 26.5 18.0
– 27.1
(85.34
– 128.02/115.71 – 173.57) (125.85 – 189.50/170.63 – 256.93) (130.19 – 196.01/176.52 – 265.76)
*M16 ×211.2
– 16.7 16.6 – 24.9 17.2 – 25.7
(81.00
– 120.79/109.83 –
163.77) (120.06 –
180.10/162.79 – 244.18) (124.40 – 186.61/168.67 – 253.01)
A bolt with an asterisk (*) is used for female screws of soft material such as cast iron.
Bolt head
marking
Nominal
size
(dia. x pitch)

GENERAL INFORMATION
9
SPECIAL PARTS FIXING NUTS AND BOLTS
Cylinder Head Cover, Cylinder Head, and Rocker Arm Shaft Bracket kgf·m(lb.ft./N·m)
1.0 –2.0
(7.2 –14.4/9.8 –19.6)
0.8 –1.8
(5.8 –13.0/7.8 –17.6)
1st Step 2nd Step
3.0 –5.0
(21.7 –36.1/29.4 –49.0) 8.2 –9.2 (59.4 –66.5/80.4 –90.2)
8.0 –9.0
(57.9 –65.1/78.4 –88.2) 10.0 –11.0 (72.4 –79.6/98.1 –107.9)
5.0 –6.0
(36.2 –43.4/49.0 –58.8)
New bolt
Reused
bolt

GENERAL INFORMATION
10
Crankshaft Bearing Cap, Connecting Rod Bearing Cap,
Crankshaft Damper Pulley, Flywheel, and Oil Pan kgf·m(lb.ft./N·m)
8.0 –9.0
(57.9 –65.1/78.4 –88.2)
16.0 –18.0
(115.7 –130.2/159.6 –176.5)
20.1 –24.5
(145.4 –177.2/197.1 –240.3)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
11.5 –12.5
(83.2 –90.4/112.8 –122.6)
14 –24
(1.4 –2.4/4.4 –7.2)

GENERAL INFORMATION
11
Timing Gear Case, Flywheel Housing, Camshaft, and Timing Gear
kgf·m(lb.ft./N·m)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
10.0 –12.0
(72.4 –86.8/98.1 –117.7)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
1.0 –1.5
(7.2 –10.9/9.8 –14.7) 6.6 –8.7
(48 –63/66 –85)
M10 x 1.25 (0.39 x 0.05) 4.6 –6.6 (33.3 –47.7/45.1 –64.7)
9.6 –11.6 (69.4 –83.9/94.1 –113.8)
8.8 –10.8 (63.7 –78.1/86.3 –105.9)
M12 x 1.25 (0.47 x 0.05)
M12 x 1.75 (0.47 x 0.07)

GENERAL INFORMATION
12
Cooling and Lubricating System
kgf·m(lb.ft./N·m)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)

GENERAL INFORMATION
13
Intake and Exhaust Manifold
kgf·m(lb.ft./N·m)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)

GENERAL INFORMATION
14
Engine Electrical
kgf·m(lb.ft./N·m)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
3.6 –4.6
(26.0 –33.3/35.3 –45.1)
2.0 –2.5
(14.4 –18.1/19.6 –24.5)
6.0 –8.0
(43.4 –57.9/58.8 –78.4)

GENERAL INFORMATION
15
Fuel Injection System
kgf·m(lb.ft./N·m)
3.2 –4.4
(23.1 –31.8/31.4 –43.2)
20 –4.0
(14.4 –28.9/19.6 –39.2)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)
1.4 –2.4
(10.1 –17.3/13.7 –23.5)

16
MEMO

MAINTENANCE
17
SECTION 2
MAINTENANCE
TABLE OF CONTENTS
ITEM PAGE
Model identification ............................................................. 18
Injection pump identification ...................................................... 18
Lubricating system .............................................................. 18
Fuel system .................................................................... 19
Cooling system ................................................................. 22
Valve clearance adjustment ....................................................... 23
Injection timing ................................................................. 24
Compression pressure measurement ............................................... 26
Recommended lubricants ......................................................... 27
Engine repair kit ................................................................ 28