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Isuzu 3AB1 Engine

The Isuzu 3AB1 is a heavy-duty, 3-cylinder, inline diesel engine engineered for high reliability, low vibration, and extended service intervals. Primarily utilized in agricultural tractors (such as the Iseki TS4510), industrial equipment, and marine auxiliary builds, the engine is characterized by a robust cast-iron cylinder block with replaceable liners. It employs an indirect injection design using a pre-combustion chamber system to optimize thermal efficiency and minimize operational noise. Valve Configuration: Overhead valve (OHV) design, featuring 2 valves per cylinder driven via a gear-train camshaft, pushrods, and rocker arms.

Maximum Power Output: Rated up to 45 horsepower (33.6 kW) at a maximum governed speed of 2600 RPM. The cylinder bore measures 86 mm (3.39 inches) and the piston stroke measures 102 mm (4.02 inches). Total engine displacement is 1.77 liters (108.4 cubic inches), utilizing a high 20:1 compression ratio. Cooling System: Liquid-cooled forced circulation utilizing a belt-driven centrifugal water pump and high-capacity radiator. Thermal regulation is managed by a pellet-type thermostat situated in the water outlet housing.

Fuel System: Employs an indirect injection architecture. Fuel delivery is synchronized by a Bosch type PES-A inline multi-cylinder injection pump driven via the main timing gear train. Atomized diesel is injected directly into the pre-combustion chamber via mechanical throttle-type nozzles at a timed interval of 16 deg BTDC. Firing order operates in a 1-3-2 sequence. Forced-feed lubrication delivered via a gear-driven oil pump. The system flows through a full-flow cartridge filter element with an integrated bypass valve. Recommended oil replacement requires high-grade diesel motor oil suitable for severe operating temperatures.

General Technical Data

Engine Specifications

Engine Model ............... Isuzu 3AB1
Engine Type ............... 4-cycle inline 3-cylinder overhead valve liquid-cooled diesel
Number of Cylinders ............... 3
Cylinder Arrangement ............... In-line vertical
Engine Bore, in (mm) ............... 3.39 (86.0)
Engine Stroke, in (mm) ............... 4.02 (102.0)
Displacement, cu.in (L) ............... 108.4 (1.777)
Rated Engine Power, hp (kW) ............... 34.5-45.0 (25.7-33.6)
Rated Engine Speed, rpm ............... 2400-2800
Peak Torque ............... 107.9 Nm (79.6 lb-ft) at 1600 rpm
Idle Speed, rpm ............... 750-850
Maximum No-Load Speed, rpm ............... 2600-3000
Aspiration Type ............... Naturally Aspirated
Compression Ratio ............... 20.0:1
Firing Order ............... 1-3-2
Direction of Rotation ............... Counter-clockwise viewed from flywheel
Cylinder Block Type ............... Monoblock cast iron with dry liners
Cylinder Head Type ............... Single-piece cast iron overhead valve design
Combustion Chamber ............... Direct injection
Valve Train Arrangement ............... Overhead valve actuated via pushrods and rocker arms
Valves per Cylinder ............... 2
Camshaft Drive Method ............... Helical gear train drive
Lubrication System ............... Full-pressure feed with gear pump
Oil Pump Type ............... Trochoid gear-driven style
Oil Filter Type ............... Full-flow cartridge spin-on
Cooling System ............... Forced circulation liquid-cooled
Water Pump Type ............... Belt-driven centrifugal impeller
Air Cleaner Type ............... Dry element dual stage filtration
Starting System ............... Electric starter motor actuation
Electrical System Voltage, V ............... 12
Alternator Capacity, A ............... 20 or 35

Fuel System

Injection Pump Type ............... Bosch PES-A in-line mechanical plunger design
Governor Type ............... Mechanical centrifugal variable speed governor
Injection Timing, deg BTDC ............... 15.0-18.0
Injection Nozzle Type ............... Multi-hole nozzle holder assembly
Nozzle Opening Pressure, psi (MPa) ............... 2560-2700 (17.6-18.6)
Fuel Transfer Pump Type ............... Camshaft-driven mechanical piston style
Fuel Filter Type ............... Spin-on element with integrated water separator
Fuel Feed Line Diameter, in (mm) ............... 0.236 (6.0)
Fuel Return Line Diameter, in (mm) ............... 0.187 (4.75)
Maximum Fuel Pump Lift, ft (m) ............... 3.3 (1.0)
Maximum Fuel Inlet Restriction, in.Hg (kPa) ............... 3.94 (13.3)
Maximum Fuel Return Restriction, in.Hg (kPa) ............... 5.92 (20.0)
Fuel Injection Pipe Outer Diameter, in (mm) ............... 0.236 (6.0)
Fuel Injection Pipe Inner Diameter, in (mm) ............... 0.078 (2.0)

Dimensions and Weight

Overall Engine Length, in (mm) ............... 23.4 (595)
Overall Engine Width, in (mm) ............... 18.9 (480)
Overall Engine Height, in (mm) ............... 25.6 (650)
Dry Engine Weight, lbs (kg) ............... 479 (217)
Wet Engine Weight, lbs (kg) ............... 512 (232)

Maintenance Data

Service Information

Minimum Oil Pressure at Idle, psi (MPa) ............... 14.2 (0.098)
Rated Lubricating Oil Pressure, psi (MPa) ............... 42.6-56.8 (0.294-0.392)
Oil Pressure Relief Valve Setting, psi (MPa) ............... 64.0 (0.441)
Thermostat Opening Temperature, F (C) ............... 170.0 (76.5)
Thermostat Full Open Temperature, F (C) ............... 194.0 (90.0)
Cooling System Operating Pressure, psi (kPa) ............... 13.0 (90.0)
Intake Valve Clearance, Cold, in (mm) ............... 0.014 (0.35)
Exhaust Valve Clearance, Cold, in (mm) ............... 0.014 (0.35)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30, 10W-30, or 15W-40
API Service Classifications ......................... CC or CD
Engine Oil Capacity with Filter, qt (L) ............... 6.66 (6.3)
Engine Oil Capacity Filter Only, qt (L) ............... 0.63 (0.6)
Coolant Capacity, Engine Block, qt (L) ............... 2.64 (2.5)
Total Coolant System Capacity, qt (L) ............... 8.45 (8.0)

Service Intervals

Change oil and filter ............... Every 250 hours
Inspect air cleaner ............... Every 100 hours
Service air cleaner ............... Every 300 hours
Replace fuel filter ............... Every 500 hours
Valve clearance adjustment ............... Every 500 hours
Fuel system inspection ............... Every 1000 hours
Change coolant ............... Every 1000 hours
Compression test ............... Every 1000 hours
Belt inspection ............... Every service cycle

Service Specifications

Cylinder Bore Standard Diameter, in (mm) ............... 3.3858-3.3874 (86.000-86.040)
Cylinder Bore Maximum Wear Limit, in (mm) ............... 3.3937 (86.200)
Cylinder Bore Out-of-Round Limit, in (mm) ............... 0.0008 (0.020)
Cylinder Head Bottom Surface Flatness, in (mm) ............... 0.0020 (0.050)
Crankshaft Main Journal Std Diameter, in (mm) ............... 2.7512-2.7520 (69.881-69.900)
Crankshaft Main Journal Wear Limit, in (mm) ............... 2.7480 (69.800)
Crankshaft Main Journal Oil Clearance, in (mm) ............... 0.0014-0.0031 (0.035-0.080)
Crankshaft Crankpin Journal Diameter, in (mm) ............... 2.0811-2.0819 (52.861-52.880)
Crankshaft Thrust Clearance, in (mm) ............... 0.0024-0.0071 (0.060-0.180)
Connecting Rod Small End Bushing ID, in (mm) ............... 1.1028-1.1035 (28.012-28.030)
Connecting Rod Bearing Oil Clearance, in (mm) ............... 0.0014-0.0028 (0.035-0.070)
Connecting Rod Big End Side Clearance, in (mm) ............... 0.0059-0.0102 (0.150-0.260)
Camshaft Journal Diameter (Front), in (mm) ............... 1.9654-1.9665 (49.920-49.950)
Camshaft Journal Diameter (Middle), in (mm) ............... 1.9260-1.9272 (48.920-48.950)
Camshaft Journal Diameter (Rear), in (mm) ............... 1.8866-1.8878 (47.920-47.950)
Camshaft Journal Oil Clearance, in (mm) ............... 0.0020-0.0035 (0.050-0.090)
Cam Height (Intake), in (mm) ............... 1.6146-1.6185 (41.010-41.110)
Cam Height (Exhaust), in (mm) ............... 1.6161-1.6201 (41.050-41.150)
Camshaft Thrust Clearance, in (mm) ............... 0.0020-0.0059 (0.050-0.150)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.3130-0.3138 (7.950-7.970)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.3118-0.3126 (7.920-7.940)
Valve Guide Bushing Inner Diameter, in (mm) ............... 0.3150-0.3157 (8.000-8.018)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0012-0.0027 (0.030-0.068)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0024-0.0039 (0.060-0.098)
Valve Spring Free Length, in (mm) ............... 1.6772 (42.600)
Piston Outer Diameter at Skirt, in (mm) ............... 3.3823-3.3835 (85.910-85.940)
Piston to Cylinder Liner Clearance, in (mm) ............... 0.0035-0.0047 (0.090-0.120)
Piston Pin Bore Diameter, in (mm) ............... 1.1024-1.1028 (28.000-28.010)
Piston Pin Outer Diameter, in (mm) ............... 1.1020-1.1024 (27.992-28.000)
Piston Pin to Piston Pin Bore Clearance, in (mm) ............... 0.0000-0.0007 (0.000-0.018)
Piston Pin to Con Rod Bushing Clearance, in (mm) ............... 0.0005-0.0015 (0.012-0.038)
Top Ring Groove Width, in (mm) ............... 0.0811-0.0823 (2.060-2.090)
Second Ring Groove Width, in (mm) ............... 0.0799-0.0807 (2.030-2.050)
Oil Ring Groove Width, in (mm) ............... 0.1783-0.1791 (4.530-4.550)
Top Ring Side Clearance, in (mm) ............... 0.0024-0.0037 (0.060-0.095)
Second Ring Side Clearance, in (mm) ............... 0.0012-0.0026 (0.030-0.065)
Oil Ring Side Clearance, in (mm) ............... 0.0008-0.0022 (0.020-0.055)
Top Ring End Gap, in (mm) ............... 0.0079-0.0157 (0.200-0.400)
Second Ring End Gap, in (mm) ............... 0.0079-0.0157 (0.200-0.400)
Oil Ring End Gap, in (mm) ............... 0.0079-0.0157 (0.200-0.400)
Tappet Outer Diameter, in (mm) ............... 0.5500-0.5506 (13.970-13.985)
Tappet to Cylinder Block Guide Clearance, in (mm) ............... 0.0006-0.0022 (0.015-0.055)
Rocker Shaft Outer Diamete, in (mm) ............... 0.7469-0.7476 (18.970-18.990)
Rocker Arm Bushing Inner Diameter, in (mm) ............... 0.7484-0.7496 (19.010-19.040)
Rocker Arm to Shaft Clearance, in (mm) ............... 0.0008-0.0028 (0.020-0.070)

Tightening Torques

Cylinder Head Bolt (M12 x 1.75) ............... 118 Nm (87.0 lb-ft)
Main Bearing Cap Bolt (M14 x 2.00) ............... 103 Nm (76.0 lb-ft)
Connecting Rod Cap Nut T(M10 x 1.25) ............... 54 Nm (39.8 lb-ft)
Flywheel Bolt (M12 x 1.25) ............... 83.4 Nm (61.5 lb-ft)
Camshaft Thrust Plate Bolt (M8 x 1.25) ............... 11.5 Nm (8.5 lb-ft)
Camshaft Timing Gear Bolt (M12) ............... 107.8 Nm (79.5 lb-ft)
Flywheel Housing Bolt (M10 x 1.25) ............... 54.9 Nm (40.5 lb-ft)
Flywheel Housing Bolt (M12 x 1.25) ............... 103.0 Nm (76.0 lb-ft)
Flywheel Housing Bolt (M12 x 1.75) ............... 96.0 Nm (71.0 lb-ft)
Crankshaft Damper Pulley Bolt ............... 196.1 Nm (144.6 lb-ft)
Rocker Shaft Bracket Bolt (M8 x 1.25) ............... 17.5 Nm (12.9 lb-ft)
Rocker Arm Cover Nut (M8 x 1.25) ............... 11.5 Nm (8.5 lb-ft)
Front Plate Bolt (M8 x 1.25) ............... 11.5 Nm (8.5 lb-ft)
Timing Gear Case Bolt (M8 x 1.25) ............... 18.6 Nm (13.7 lb-ft)
Oil Pan Drain Plug ............... 54.0 Nm (39.8 lb-ft)
Oil Pan Securing Bolt (M8 x 1.25) ............... 11.5 Nm (8.5 lb-ft)
Oil Pump Assembly Bolt (M8) ............... 17.6 Nm (13.0 lb-ft)
Water Pump Assembly Bolt (M8) ............... 18.6 Nm (13.7 lb-ft)
Exhaust Manifold Stud Nut (M8) ............... 24.5 Nm (18.1 lb-ft)
Intake Manifold Securing Bolt (M8) ............... 18.6 Nm (13.7 lb-ft)
Fuel Injection Nozzle Holder (M20 x 1.5) ............... 58.9 Nm (43.4 lb-ft)
Fuel Injection Nozzle Retaining Cap Nut (M16 x 0.75) ............... 36.8 Nm (27.1 lb-ft)
Fuel Injection Pump Drive Gear Nut (M12 x 1.75) ............... 63.7 Nm (47.0 lb-ft)
Fuel Injection Pump Overflow Valve ............... 17.5 Nm (12.9 lb-ft)
Fuel Injection High Pressure Pipe Nut (M12 x 1.5) ............... 29.5 Nm (21.8 lb-ft)
Fuel Return Pipe Leak-Off Nut (M10 x 1.25) ............... 19.7 Nm (14.5 lb-ft)
Glow Plug Torque (M10 x 1.25) ............... 24.5 Nm (18.1 lb-ft)
Oil Pressure Switch Sensor ............... 14.7 Nm (10.8 lb-ft)
Coolant Temperature Sensor ............... 29.4 Nm (21.7 lb-ft)
Starter Motor Mounting Bolt (M10) ............... 39.2 Nm (28.9 lb-ft)
Alternator Mounting Bolt Main Pivot ............... 44.1 Nm (32.5 lb-ft)
Alternator Adjusting Lock Bolt ............... 18.6 Nm (13.7 lb-ft)
Thermostat Housing Bolt (M8) ............... 18.6 Nm (13.7 lb-ft)
Fan Blade Securing Bolt (M6) ............... 9.8 Nm (7.2 lb-ft)
Cylinder Head Side Cover Bolt (M6) ............... 7.8 Nm (5.8 lb-ft)
Cylinder Head Plug (M16 x 1.5) ............... 44.1 Nm (32.5 lb-ft)

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• Isuzu Engines Specs
  
• Isuzu 2AA1 Specs
  
• Isuzu 3AA1 Specs
  
• Isuzu 3CB1 Specs
  
• Isuzu 3CD1 Specs
  
• Isuzu 3CE1 Specs
  
• Isuzu 3CH1 Specs
  

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