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Yanmar 3D84 Engine

The Yanmar 3D84 (also designated across various joint applications as the 3TNE84 / 3TNV84 or Komatsu 3D84E) is an industrial-grade, vertical, in-line 3-cylinder, 4-cycle water-cooled diesel engine. Widely deployed across compact agricultural machinery, mini excavators, generators, and utility platforms, this engine family is highly regarded for its robust mechanical design, structural longevity, and exceptional thermal efficiency. It is engineered primarily for off-road durability, delivering high torque density within a compact footprint while complying with modern emissions regulations via optimized combustion tech.

Valve Configuration: Overhead Valve (OHV) mechanism driven via a gear-train operated camshaft, pushrods, and rocker arms. Total Valves: 6 valves total (2 valves per cylinder: 1 intake, 1 exhaust). Service Adjustment: Mechanical clearance adjustments are executed at the rocker arm adjusting screws. Cylinder Bore: 84 mm (3.3 inches). Piston Stroke: 90 mm (3.5 inches). Total Displacement: 1.496 Liters (91.3 cubic inches).

Fuel System: Direct Injection (DI) system utilized for improved fuel economy and reduced cold-start smoke. Certain baseline or early legacy industrial models utilize an indirect pre-combustion chamber design. Injection Pump: Inline or block-type mechanical high-pressure fuel injection pump driven via the main timing gear train. Governor Assembly: All-speed mechanical centrifugal governor integrated directly onto the injection pump drive housing to handle varying load demands. Shut-off Mechanism: 12-Volt DC electric fuel shutdown solenoid acting directly on the injection pump rack to stop fuel flow when key power is isolated.

Lubrication System: Forced pressure lubrication system. Oil Pump Type: Engine-driven trochoid pump integrated into the gear housing. Filtration: Full-flow, replaceable spin-on element cartridge filter with an internal bypass valve safety reset. Cooling System: Liquid-cooled, forced-circulation configuration. Circulation Pump: Belt-driven centrifugal water pump working alongside an engine-mounted cooling fan. Temperature Control: Wax-pellet type bypass thermostat designed to maintain structural operating temperatures within optimal parameters.

General Technical Data

Engine Specifications

Engine Model ............... Yanmar 3D84
Engine Type ............... 4-cycle vertical inline liquid-cooled diesel
Number of Cylinders ............... 3
Cylinder Arrangement ............... In-line vertical
Engine Bore, in (mm) ............... 3.31 (84.0)
Engine Stroke, in (mm) ............... 3.54 (90.0)
Displacement, cu.in (L) ............... 91.3 (1.496)
Rated Engine Power, hp (kW) ............... 38.0 (28.3)
Rated Engine Speed, rpm ............... 2700-3600
Peak Torque ............... 70.1-77.4 lb-ft (95-105 Nm) at 1900-2100 rpm
Low Idle Speed, rpm ............... 750-850
High Idle Speed, rpm ............... 2900-3800
Aspiration Type ............... Naturally Aspirated
Compression Ratio ............... 18.0:1
Firing Order ............... 1-2-3
Direction of Rotation ............... Counterclockwise viewed from flywheel side
Combustion Chamber ............... Direct injection toroidal piston crown
Cylinder Block Type ............... High-strength cast iron
Cylinder Head Type ............... Monoblock cast iron
Lubrication System ............... Forced pressure feed by trochoid pump
Oil Pump Type ............... Trochoid type crankshaft-driven gear
Oil Filter Type ............... Full-flow spin-on element cartridge
Cooling System ............... Forced liquid circulation with radiator
Water Pump Type ............... Belt-driven centrifugal pump
Air Cleaner Type ............... Dry element dual-stage heavy duty
Starting System ............... Electric starter motor electronic control
Electrical System ............... 12V DC

Fuel System

Fuel Injection Pump Type ............... In-line jerk pump cassette unit
Fuel Injection Pump Model ............... Yanmar YPES type mini pump
Fuel Feed Pump Type ............... Mechanical diaphragm type pull lever
Fuel Injection Nozzle Type ............... Multi-hole throttle nozzle pattern
Number of Nozzle Holes ............... 4 holes configuration
Nozzle Hole Diameter, in (mm) ............... 0.0098 (0.25)
Fuel Injection Opening Pressure, psi (MPa) ............... 2842-2987 (19.6-20.6)
Fuel Injection Timing, deg BTDC ............... 14.0-16.0
Governor Type ............... Centrifugal all-speed mechanical governor
Fuel Filter Type ............... Spin-on cartridge type paper element separator
Fuel Transfer Pump Pressure, psi (bar) ............... 2.9-4.3 (0.2-0.3)
Maximum Fuel Inlet Restriction, in-Hg (kPa) ............... 3.9 (13.3)
Maximum Fuel Return Restriction, in-Hg (kPa) ............... 5.9 (20.0)
Recommended Fuel Grade ............... ASTM D975 Number 2-D ultra-low sulfur
Plunger Diameter, in (mm) ............... 0.236 (6.0)
Plunger Stroke, in (mm) ............... 0.275 (7.0)
Delivery Valve Standard Opening Pressure, psi (MPa) ............... 355 (2.45)
Fuel Line Outer Diameter, in (mm) ............... 0.236 (6.0)
Fuel Line Inner Diameter, in (mm) ............... 0.078 (2.0)
High Pressure Line Length, in (mm) ............... 15.74 (400.0)
Fuel Tank Vent Air Flow Capacity, cfm (L/min) ............... 1.41 (40.0)

Dimensions and Weight

Overall Length, in (mm) ............... 23.2 (590)
Overall Width, in (mm) ............... 19.1 (485)
Overall Height, in (mm) ............... 24.5 (625)
Dry Weight, lbs (kg) ............... 355 (161)
Wet Weight, lbs (kg) ............... 375 (170)

Maintenance Data

Service Information

Compression Pressure (Standard), psi (MPa) ............... 426-469 (2.94-3.23)
Compression Pressure (Minimum), psi (MPa) ............... 355 (2.45)
Maximum Cylinder Pressure Variance, psi (MPa) ............... 28.4 (0.196)
Oil Pressure at Rated Speed, psi (MPa) ............... 42.6-56.8 (0.29-0.39)
Oil Pressure at Idle Speed, psi (MPa) ............... 8.5 (0.058)
Radiator Cap Relief Valve Opening Pressure, psi (kPa) ............... 12.8 (88.2)
Standard Oil Sump Temperature, F (C) ............... 185-230 (85-110)
Standard Coolant Temperature Range, F (C) ............... 167-194 (75-90)
Thermostat Valve Opening Temperature, F (C) ............... 160 (71.0)
Thermostat Full Open Temperature, F (C) ............... 185 (85.0)
Alternator Belt Deflection under 22 lbs Force, in (mm) ............... 0.39 (10.0)
Intake Valve Clearance, Cold, in (mm) ............... 0.0059-0.0078 (0.150-0.200)
Exhaust Valve Clearance, Cold, in (mm) ............... 0.0059-0.0078 (0.150-0.200)

Engine Oil and Coolant

Engine Oil Type .................. SAE 5W-30, SAE 10W-30, or SAE 15W-40
API Service Classifications ......................... CI-4, CK-4
Engine Oil Capacity with Filter, qt (L) ............... 5.8 (5.5)
Engine Oil Capacity (Sump Only), qt (L) ............... 5.2 (4.9)
Cooling Capacity (Engine Only), qt (L) ............... 2.8 (2.7)
Cooling Capacity with Radiator, qt (L) ............... 6.3 (6.0)

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
Clean radiator core ............... Every 200 hours
Inspect belt tension ............... Every 100 hours

Service Specifications

Cylinder Bore Inner Diameter, in (mm) ............... 3.3070-3.3074 (84.000-84.010)
Cylinder Bore Maximum, Wear Limit, in (mm) ............... 3.3150 (84.200)
Cylinder Bore Out of Round, Limit, in (mm) ............... 0.0004 (0.010)
Cylinder Block Top Surface Flatness, in (mm) ............... 0.0019 (0.05)
Crankshaft Main Journal Outer Diameter, in (mm) ............... 1.9665-1.9671 (49.950-49.965)
Crankpin Journal Outer Diameter, in (mm) ............... 1.7696-1.7702 (44.950-44.965)
Crankshaft Main Journal Clearance, in (mm) ............... 0.0015-0.0033 (0.040-0.085)
Crankpin Oil Clearance, in (mm) ............... 0.0015-0.0031 (0.040-0.080)
Crankshaft End Play, in (mm) ............... 0.0043-0.0094 (0.110-0.240)
Connecting Rod Small End Bushing I.D, in (mm) ............... 1.0244-1.0251 (26.020-26.038)
Connecting Rod Big End Bore Inner Diameter, in (mm) ............... 1.8897-1.8903 (48.000-48.015)
Connecting Rod to Piston Pin Bushing Clearance, in (mm) ............... 0.0007-0.0018 (0.020-0.046)
Connecting Rod Big End Side Clearance, in (mm) ............... 0.0078-0.0157 (0.200-0.400)
Piston Skirt Outer Diameter, in (mm) ............... 3.3049-3.3053 (83.945-83.955)
Piston to Cylinder Bore Clearance, in (mm) ............... 0.0017-0.0025 (0.045-0.065)
Piston Pin Bore Inner Diameter, in (mm) ............... 1.0236-1.0240 (26.000-26.009)
Piston Pin Outer Diameter, in (mm) ............... 1.0233-1.0236 (25.992-26.000)
Piston Pin to Piston Pin Bore Clearance, in (mm) ............... 0.0000-0.0006 (0.000-0.017)
Top Ring Groove Width, in (mm) ............... 0.0787-0.0795 (2.000-2.020)
Second Ring Groove Width, in (mm) ............... 0.0787-0.0795 (2.000-2.020)
Oil Ring Groove Width, in (mm) ............... 0.1574-0.1582 (4.000-4.020)
Top Ring Side Clearance, in (mm) ............... 0.0027-0.0041 (0.070-0.105)
Second Ring Side Clearance, in (mm) ............... 0.0015-0.0029 (0.040-0.075)
Oil Ring Side Clearance, in (mm) ............... 0.0007-0.0021 (0.020-0.055)
Top Ring End Gap, in (mm) ............... 0.0078-0.0157 (0.200-0.400)
Second Ring End Gap, in (mm) ............... 0.0078-0.0157 (0.200-0.400)
Oil Ring End Gap, in (mm) ............... 0.0078-0.0157 (0.200-0.400)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.2736-0.2742 (6.950-6.965)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.2732-0.2738 (6.940-6.955)
Intake Valve Guide Inner Diameter, in (mm) ............... 0.2755-0.2761 (7.000-7.015)
Exhaust Valve Guide Inner Diameter, in (mm) ............... 0.2755-0.2761 (7.000-7.015)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0013-0.0025 (0.035-0.065)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0017-0.0029 (0.045-0.075)
Intake Valve Seat Width, in (mm) ............... 0.0413-0.0531 (1.050-1.350)
Exhaust Valve Seat Width, in (mm) ............... 0.0433-0.0551 (1.100-1.400)
Valve Face Angle, deg ............... 45
Valve Seat Angle, deg ............... 45
Valve Spring Free Length, in (mm) ............... 1.4881 (37.800)
Valve Recess Depth, in (mm) ............... 0.0157-0.0236 (0.400-0.600)
Camshaft Journal Outer Diameter, in (mm) ............... 1.5728-1.5734 (39.950-39.965)
Camshaft Journal Bearing Inner Diameter, in (mm) ............... 1.5748-1.5757 (40.000-40.025)
Camshaft Journal Oil Clearance, in (mm) ............... 0.0013-0.0029 (0.035-0.075)
Intake Cam Lobe Height, in (mm) ............... 1.3326-1.3366 (33.850-33.950)
Exhaust Cam Lobe Height, in (mm) ............... 1.3346-1.3385 (33.900-34.000)
Camshaft End Play, in (mm) ............... 0.0019-0.0059 (0.050-0.150)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.4716-0.4722 (11.980-11.995)
Rocker Arm Bushing Inner Diameter, in (mm) ............... 0.4724-0.4732 (12.000-12.020)
Rocker Arm Shaft to Bushing Clearance, in (mm) ............... 0.0001-0.0015 (0.005-0.040)

Tightening Torques

Cylinder Head Bolt (M10) ............... 54.2-57.9 lb-ft (73.5-78.5 Nm)
Cylinder Head Bolt (M12) ............... 72.3-75.9 lb-ft (98.0-103.0 Nm)
Connecting Rod Cap Bolt ............... 39.1-42.7 lb-ft (53.0-58.0 Nm)
Main Bearing Cap Bolt (M10) ............... 57.9-61.5 lb-ft (78.5-83.5 Nm)
Main Bearing Cap Bolt (M12) ............... 75.9-79.6 lb-ft (103.0-108.0 Nm)
Flywheel Retaining Bolt ............... 61.5-65.1 lb-ft (83.5-88.5 Nm)
Crankshaft V-Pulley End Nut ............... 83.1-90.4 lb-ft (112.7-122.6 Nm)
Camshaft Gear Lock Bolt ............... 57.9-65.1 lb-ft (78.5-88.5 Nm)
Idle Gear Shaft Bolt ............... 17.3-21.6 lb-ft (23.5-29.4 Nm)
Rocker Arm Shaft Support Bolt ............... 17.3-21.6 lb-ft (23.5-29.4 Nm)
Valve Bonnet Cover Nut ............... 6.5-8.6 lb-ft (8.8-11.8 Nm)
Injection Nozzle Holder Bolt ............... 17.3-21.6 lb-ft (23.5-29.4 Nm)
Injection Pump Delivery Valve Holder Bolt ............... 25.3-28.9 lb-ft (34.3-39.2 Nm)
Injection Pump Coupling Joint Drive Bolt ............... 17.3-21.6 lb-ft (23.5-29.4 Nm)
High Pressure Injection Pipe Flare Nut ............... 21.6-25.3 lb-ft (29.4-34.3 Nm)
Fuel Return Pipe Joint Hollow Bolt ............... 14.4-18.1 lb-ft (19.6-24.5 Nm)
Oil Sump Drain Plug ............... 28.9-36.1 lb-ft (39.2-49.0 Nm)
Oil Pressure Switch Sensor ............... 7.2-10.8 lb-ft (9.8-14.7 Nm)
Coolant Temperature Sensor ............... 14.4-21.6 lb-ft (19.6-29.4 Nm)
Glow Plug Terminal Small Nut ............... 0.7-1.0 lb-ft (1.0-1.5 Nm)
Glow Plug Body Core ............... 10.8-14.4 lb-ft (14.7-19.6 Nm)
Starter Motor Terminal Lead Nut ............... 5.7-8.6 lb-ft (7.8-11.8 Nm)
Starter Motor Mounting Flange Bolt ............... 28.9-36.1 lb-ft (39.2-49.0 Nm)
Alternator Pivot Mount Support Bolt ............... 28.9-36.1 lb-ft (39.2-49.0 Nm)
Alternator Adjusting Brace Locking Bolt ............... 14.4-18.1 lb-ft (19.6-24.5 Nm)
Exhaust Manifold Shield Nut ............... 17.3-21.6 lb-ft (23.5-29.4 Nm)
Intake Manifold Flange Fastener ............... 17.3-21.6 lb-ft (23.5-29.4 Nm)
Oil Pump Rotor Cover Plate Screw ............... 5.0-7.2 lb-ft (6.8-9.8 Nm)
Water Pump Housing Mounting Bolt ............... 17.3-21.6 lb-ft (23.5-29.4 Nm)
Cooling Fan Blade Stud Nut ............... 5.0-7.2 lb-ft (6.8-9.8 Nm)
Flywheel Housing Back Plate Bolt ............... 28.9-36.1 lb-ft (39.2-49.0 Nm)
Gear Housing Shield Front Plate Bolt ............... 17.3-21.6 lb-ft (23.5-29.4 Nm)
Lubricating Oil Pipe Flange Bolt ............... 14.4-18.1 lb-ft (19.6-24.5 Nm)

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