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Isuzu 3KR1 Engine

The Isuzu 3KR1 is an industrial, inline 3-cylinder, water-cooled, 4-cycle diesel engine. It belongs to the same engine family as the 3KC1 and 3KR2 units and is prominently deployed in light industrial equipment, mini-excavators (such as the Hitachi EX series), generators, and agricultural tractors. Engineered for high structural durability and simplified mechanical upkeep, it features a heavy-duty cast iron block and a streamlined top-end layout designed to withstand continuous load operation.

The valvetrain utilizes an Overhead Camshaft (OHC) layout. It is configured with 2 valves per cylinder (1 intake valve and 1 exhaust valve), operated via a high-durability gear and chain timing drive system. Valve adjustment must be performed when the engine is completely cold. The engine has a displacement of 1.4 liters (1381 cc). Its dimensions feature a bore of 81.0 mm and a stroke of 89.4 mm.

The fuel system is built around a mechanical indirect injection system utilizing a highly efficient swirl combustion chamber design. It features an inline or cassette-type mechanical fuel injection pump, a mechanical governor assembly to control engine speed under variable loads, and low-inertia nozzle holder assemblies containing the fuel injectors. Fuel delivery from the main tank is sustained by a mechanical fuel supply lift pump, feeding through a spin-on fuel filter and water separator element. Glow plugs are integrated directly into the cylinder head swirl chambers to facilitate reliable pre-heating and cold-weather starting.

Lubrication is managed via a full-pressure feed system driven by a dedicated, crankshaft-driven internal oil pump. It incorporates a spin-on full-flow oil filter, a pressure regulating relief valve, and an integrated oil pan (sump). System monitoring is routed through an electrical oil pressure switch mounted on the main oil gallery. Engine cooling uses a forced liquid-circulation loop. The assembly features a belt-driven centrifugal water pump that forces coolant through the cylinder block and cylinder head passages. System temperature regulation is governed by a wax-pellet type thermostat which controls flow diversion to an external radiator fan unit.

General Technical Data

Engine Specifications

Engine Model ............... Isuzu 3KR1
Engine Type ............... 4-cycle inline 3-cylinder indirect injection liquid-cooled diesel
Number of Cylinders ............... 3
Cylinder Arrangement ............... In-line vertical
Engine Bore, in (mm) ............... 3.19 (81.0)
Engine Stroke, in (mm) ............... 3.62 (92.0)
Displacement, cu.in (L) ............... 86.8 (1.422)
Rated Engine Power, hp (kW) ............... 32.0 (23.9)
Rated Engine Speed, rpm ............... 3000
Peak Torque, lb-ft (Nm) ............... 64.9 (88.0) at 1800 rpm
Idle Speed, rpm ............... 800-900
Maximum No-Load Speed, rpm ............... 3200-3300
Aspiration Type ............... Naturally aspirated
Compression Ratio ............... 22.0:1
Firing Order ............... 1-3-2
Direction of Rotation ............... Counterclockwise viewed from flywheel
Cylinder Block Material ............... High-strength cast iron
Cylinder Head Material ............... Cast iron alloy
Cylinder Liner Type ............... Dry type, chromate treated
Combustion Chamber Design ............... Swirl chamber type, indirect injection
Valve Mechanism System ............... Overhead valve, gear-driven camshaft
Number of Valves per Cylinder ............... 2
Lubrication System Method ............... Full-pressure feed via trochoid pump
Oil Pump Drive Mechanism ............... Gear-driven from crankshaft gear
Oil Filter Assembly Type ............... Full-flow, replaceable spin-on element
Cooling System Method ............... Liquid-cooled forced circulation
Water Pump Assembly Type ............... Belt-driven centrifugal impeller
Cooling Fan Configuration ............... Suction type or pusher type
Air Cleaner Filter Configuration ............... Dry dual-stage heavy-duty element
Starting System Configuration ............... Electric starter motor actuation
Electrical System Voltage, V ............... 12
Alternator Output Capacity, A ............... 20-35

Fuel System

Fuel Injection Pump Assembly Model ............... Diesel Kiki Bosch P-type mini inline unit
Fuel Feed Pump Type ............... Mechanical piston type driven by injection pump camshaft
Fuel Injection Timing, deg BTDC ............... 16.0
Fuel Injector Nozzle Holder Model ............... Diesel Kiki throttle type assembly
Fuel Injector Nozzle Tip Style ............... Pintle orifice design
Initial Injection Opening Pressure, psi (MPa) ............... 1991.0 (13.73)
Injection Valve Seat Leakage Pressure, psi (MPa) ............... 1706.0 (11.76)
Fuel Filter Construction ............... Spin-on cartridge with integrated water sedimenter
Fuel Priming Pump Type ............... Manual plunger style on fuel feed pump body
Fuel Tank Vent Pressure Limit, psi (kPa) ............... 0.14 (1.0)
Governor System Mechanism ............... Mechanical centrifugal type
Fuel System Delivery Line Material ............... Double-wall high-pressure steel seamless tubing
Fuel Return Pipe Configuration ............... Overflow pipe routed back to primary fuel reservoir
Injection Pump Plunger Outer Diameter, in (mm) ............... 0.216 (5.5)
Injection Pump Plunger Stroke Length, in (mm) ............... 0.275 (7.0)
Delivery Valve Cracking Pressure, psi (MPa) ............... 355.0 (2.45)
Fuel Supply Line Outer Diameter, in (mm) ............... 0.315 (8.0)
Fuel Return Line Outer Diameter, in (mm) ............... 0.236 (6.0)

Dimensions and Weight

Overall Length, in (mm) ............... 21.8 (555)
Overall Width, in (mm) ............... 18.1 (460)
Overall Height, in (mm) ............... 23.4 (595)
Dry Weight, lbs (kg) ............... 282 (128)
Wet Weight with Fluids, lbs (kg) ............... 305 (138)

Maintenance Data

Service Information

Standard Compression Pressure, psi (MPa) ............... 441.0 (3.04)
Minimum Compression Pressure, psi (MPa) ............... 370.0 (2.55)
Compression Pressure Between Cylinders, psi (MPa) ............... 28.4 (0.19)
Oil Pressure at Idle Speed, psi (kPa) ............... 14.2 (98.0)
Oil Pressure at Rated Speed, psi (kPa) ............... 42.6-56.8 (294.0-392.0)
Radiator Cap Pressure Valve Relief Setting, psi (kPa) ............... 12.8 (88.2)
Coolant Operating Temperature Range, F (C) ............... 176.0-194.0 (80.0-90.0)
Thermostat Opening Start Temperature, F (C) ............... 170.0 (76.5)
Thermostat Fully Open Temperature, F (C) ............... 194.0 (90.0)
Fan Belt Deflection, Standard Push Force, lbs (N) ............... 22.0 (98.0)
Fan Belt Deflection, Under Standard Force, in (mm) ............... 0.39-0.47 (10.0-12.0)
Intake Valve Clearance (Cold), in (mm) ............... 0.012 (0.25)
Exhaust Valve Clearance (Cold), in (mm) ............... 0.012 (0.25)

Engine Oil and Coolant

Engine Oil Type .................. SAE 20W-20, 10W-30, or SAE 15W-40
API Service Classifications ......................... CD or CE
Engine Oil Capacity, High Level, qts (L) ............... 4.75 (4.5)
Engine Oil Capacity, Low Level, qts (L) ............... 3.17 (3.0)
Oil Filter Element Fluid Capacity, qts (L) ............... 0.31 (0.3)
Total Engine Oil Capacity, qts (L) ............... 5.07 (4.8)
Coolant Capacity, Internal Passages, qts (L) ............... 2.32 (2.2)

Service Intervals

Change oil and filter ............... Every 250 hours
Inspect air cleaner ............... Every 100 hours
Replace air cleaner ............... Every 1000 hours
Replace fuel filter ............... Every 500 hours
Valve clearance adjustment ............... Every 500 hours
Fuel system inspection ............... Every 1000 hours
Change coolant ............... Every 2000 hours
Compression test ............... Every 1000 hours
Belt inspection ............... Every service cycle

Service Specifications

Cylinder Block Top Surface Flatness, in (mm) ............... 0.002 (0.05)
Cylinder Liner Inside Diameter (Grade A), in (mm) ............... 3.1889-3.1893 (81.000-81.011)
Cylinder Liner Inside Diameter (Grade B), in (mm) ............... 3.1893-3.1897 (81.011-81.022)
Cylinder Liner Cylindricity and Taper Std Value, in (mm) ............... 0.0004 (0.01)
Cylinder Liner Projection Above Block Top Surface, in (mm) ............... 0.0023-0.0035 (0.06-0.09)
Crankshaft Crankpin Journal Diameter, in (mm) ............... 1.8881-1.8887 (47.959-47.975)
Crankshaft Main Journal Diameter, in (mm) ............... 2.0456-2.0462 (51.959-51.975)
Crankshaft Main Bearing Oil Clearance, in (mm) ............... 0.0013-0.0029 (0.034-0.073)
Crankshaft End Play, in (mm) ............... 0.0023-0.0055 (0.060-0.140)
Crankshaft Main Journal Thrust Bearing Width, in (mm) ............... 0.8228-0.8244 (20.900-20.940)
Crankshaft Center Journal Width, in (mm) ............... 0.8267-0.8283 (21.000-21.042)
Connecting Rod Small End Bushing Inside Diameter, in (mm) ............... 0.9845-0.9851 (25.008-25.023)
Connecting Rod Big End Side Clearance, in (mm) ............... 0.0039-0.0078 (0.10-0.20)
Connecting Rod Bearing Oil Clearance, in (mm) ............... 0.0014-0.0029 (0.035-0.074)
Piston Pin to Small End Bushing Clearance, in (mm) ............... 0.0003-0.0011 (0.008-0.028)
Piston Outer Diameter (Grade A), in (mm) ............... 3.1866-3.1870 (80.941-80.952)
Piston Outer Diameter (Grade B), in (mm) ............... 3.1870-3.1874 (80.952-80.963)
Piston to Cylinder Liner Clearance, in (mm) ............... 0.0018-0.0027 (0.047-0.070)
Top Ring Groove Width, in (mm) ............... 0.081-0.082 (2.05-2.07)
Second Ring Groove Width, in (mm) ............... 0.080-0.081 (2.03-2.05)
Oil Ring Groove Width, in (mm) ............... 0.158-0.159 (4.01-4.03)
Top Ring Side Clearance, in (mm) ............... 0.0023-0.0035 (0.06-0.09)
Second Ring Side Clearance, in (mm) ............... 0.0019-0.0031 (0.05-0.08)
Oil Ring Side Clearance, in (mm) ............... 0.0011-0.0027 (0.03-0.07)
Top Ring End Gap, in (mm) ............... 0.0078-0.0137 (0.20-0.35)
Second Ring End Gap, in (mm) ............... 0.0078-0.0137 (0.20-0.35)
Oil Ring End Gap, in (mm) ............... 0.0078-0.0177 (0.20-0.45)
Piston Pin Bore Inside Diameter, in (mm) ............... 0.9844-0.9846 (25.005-25.011)
Piston Pin Outer Diameter, in (mm) ............... 0.9841-0.9843 (24.995-25.000)
Piston Pin to Piston Pin Bore Clearance, in (mm) ............... 0.0001-0.0006 (0.005-0.016)
Cylinder Head Lower Surface Flatness, in (mm) ............... 0.0019 (0.05)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.2736-0.2742 (6.950-6.965)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.2724-0.2732 (6.920-6.940)
Valve Guide Inside Diameter, in (mm) ............... 0.2755-0.2761 (7.000-7.015)
Intake Valve Stem to Valve Guide Clearance, in (mm) ............... 0.0013-0.0025 (0.035-0.065)
Exhaust Valve Stem to Valve Guide Clearance, in (mm) ............... 0.0023-0.0037 (0.060-0.095)
Intake Valve Seat Contact Width, in (mm) ............... 0.0472-0.0551 (1.20-1.40)
Exhaust Valve Seat Contact Width, in (mm) ............... 0.0472-0.0551 (1.20-1.40)
Valve Spring Free Length, in (mm) ............... 1.665 (42.3)
Camshaft Journal Outer Diameter (Front), in (mm) ............... 1.5731-1.5739 (39.959-39.975)
Camshaft Journal Outer Diameter (Middle), in (mm) ............... 1.5338-1.5344 (38.959-38.975)
Camshaft Journal Outer Diameter (Rear), in (mm) ............... 1.4944-1.4950 (37.959-37.975)
Camshaft Journal Bearing Oil Clearance, in (mm) ............... 0.0009-0.0029 (0.025-0.075)
Cam Lobe Height (Intake), in (mm) ............... 1.3051 (33.150)
Cam Lobe Height (Exhaust), in (mm) ............... 1.3051 (33.150)
Camshaft End Play, in (mm) ............... 0.0019-0.0059 (0.050-0.150)
Tappet Outer Diameter, in (mm) ............... 0.4712-0.4718 (11.970-11.985)
Cylinder Block Tappet Guide Bore ID, in (mm) ............... 0.4724-0.4731 (12.000-12.018)
Tappet to Tappet Guide Bore Clearance, in (mm) ............... 0.0005-0.0018 (0.015-0.048)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.4714-0.4720 (11.973-11.988)
Rocker Arm Bushing Inside Diameter, in (mm) ............... 0.4724-0.4736 (12.000-12.030)
Rocker Arm to Shaft Radial Oil Clearance, in (mm) ............... 0.0004-0.0022 (0.012-0.057)

Tightening Torques

Cylinder Head Bolt, lb-ft (Nm) ............... 83.2-97.6 (112.8-132.4)
Main Bearing Cap Bolt, lb-ft (Nm) ............... 54.2-61.5 (73.5-83.4)
Connecting Rod Cap Nut, lb-ft (Nm) ............... 54.2-61.5 (73.5-83.4)
Flywheel Bolt, lb-ft (Nm) ............... 57.9-65.1 (78.5-88.3)
Crankshaft Damper Pulley Bolt, lb-ft (Nm) ............... 108.5-122.9 (147.1-166.7)
Camshaft Gear Bolt, lb-ft (Nm) ............... 43.4-50.6 (58.8-68.6)
Rocker Arm Shaft Bracket Bolt, lb-ft (Nm) ............... 15.9-21.7 (21.6-29.4)
Cylinder Head Cover Nut, lb-ft (Nm) ............... 5.8-8.7 (7.8-11.8)
Oil Pan Drain Plug, lb-ft (Nm) ............... 36.2-43.4 (49.0-58.8)
Oil Pan Mounting Bolt, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)
Timing Gear Case Bolt, lb-ft (Nm) ............... 13.0-17.4 (17.7-23.5)
Timing Gear Case Cover Bolt, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)
Injection Pump Drive Gear Nut, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Injection Pump Retaining Nut, lb-ft (Nm) ............... 13.0-17.4 (17.7-23.5)
Injection Nozzle Assembly Holder, lb-ft (Nm) ............... 36.2-43.4 (49.0-58.8)
Injection Pipe Gland Nut, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Fuel Overflow Pipe Clip Bolt, lb-ft (Nm) ............... 5.8-8.7 (7.8-11.8)
Glow Plug Torque, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Oil Pressure Switch, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Water Temperature Sensor, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Cooling Fan Bolt, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)
Water Pump Mounting Bolt, lb-ft (Nm) ............... 13.0-17.4 (17.7-23.5)
Thermostat Housing Bolt, lb-ft (Nm) ............... 13.0-17.4 (17.7-23.5)
Intake Manifold Bolt, lb-ft (Nm) ............... 13.0-17.4 (17.7-23.5)
Exhaust Manifold Bolt, lb-ft (Nm) ............... 15.9-21.7 (21.6-29.4)
Starter Motor Mounting Bolt, lb-ft (Nm) ............... 54.2-61.5 (73.5-83.4)
Alternator Mounting Bolt Main, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Alternator Adjusting Lock Bolt, lb-ft (Nm) ............... 13.0-17.4 (17.7-23.5)
Oil Pump Cover Plate Screw, lb-ft (Nm) ............... 3.6-5.1 (4.9-6.9)
Oil Relief Valve Plug, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Flywheel Housing Bolt, lb-ft (Nm) ............... 36.2-43.4 (49.0-58.8)
Rear Oil Seal Retainer Bolt, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)
Front Oil Seal Retainer Bolt, lb-ft (Nm) ............... 7.2-10.1 (9.8-13.7)
Main Oil Gallery End Plug, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Idler Gear Shaft Bolt, lb-ft (Nm) ............... 18.1-24.6 (24.5-33.3)

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• Isuzu Engines Specs
  
• Isuzu 3KC1 Specs
  
• Isuzu 3KC2 Specs
  
• Isuzu 3KR2 Specs
  
• Isuzu 3LB1 Specs
  
• Isuzu 3LD1 Specs
  
• Isuzu 3LD2 Specs
  

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