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Yanmar 3TN78 Specifications

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• Yanmar 3TN78 Engine Specifications
• Yanmar 3TN78 Engine Troubleshooting

Engine Model ................ Yanmar 3TN78
Engine Type ................ 4-Cycle direct injection liquid-cooled diesel
Number of Cylinders ................ 3
Cylinder Bore, mm (in) ................ 78.0 (3.07)
Piston Stroke, mm (in) ................ 86.0 (3.39)
Total Displacement, L (cu.in) ................ 1.15 (69.9)
Rated Engine Power, kW (hp) ................ 17.0 (23.0)
Fast Idle Speed, rpm ................ 2450
Slow Idle Speed, rpm ................ 800
Aspiration Type ................ Naturally aspirated
Crankshaft Alignment ................ Horizontal
Compression Ratio ................ 17.75:1
Firing Order ................ 1-3-2
Air Cleaner ................ Dry element with precleaner
Lubrication System ................ Full pressure
Oil Filter Type ................ Full flow, replaceable
Electrical System Rating, Volts ................ 12
Charging System ................ Alternator
Alternator Rating, Amps ................ 25

Fuel System ................ Direct injection
Fuel Pump Type ................ Mechanical
Governor Type ................ Mechanical
Fuel Type ................ Diesel Fuel

Cylinder Bore Clearance, mm (in) ................ 0.22 (0.009)
Cylinder Bore I.D (Std), mm (in) ................ 78.00-78.03 (3.071-3.072)
Cylinder Bore I.D (Wear Limit), mm (in) ................ 78.20 (3.079)
Cylinder Bore I.D (0.25 mm Oversize), mm (in) ................ 78.25-78.28 (3.081-3.082)
Cylinder Bore I.D (0.50 mm Oversize), mm (in) ................ 78.50-78.53 (3.091-3.092)
Crankshaft End Play, mm (in) ................ 0.090-0.271 (0.004-0.011)
Crankshaft Main Bearing Clearance, mm (in) ................ 0.038-0.090 (0.0015-0.0035)
Connecting Rod Journal O.D (Std), mm (in) ................ 42.952-42.962 (1.6910-1.6914)
Connecting Rod Journal O.D (Wear Limit), mm (in) ................ 42.91 (1.689)
Connecting Rod Bearing Clearance, mm (in) ................ 0.16 (0.006)
Connecting Rod Bearing I.D (Std), mm (in) ................ 43.00-43.042 (1.693-1.695)
Connecting Rod Bearing I.D (Wear Limit), mm (in) ................ 43.07 (1.696)
Main Bearing Journal O.D (Std), mm (in) ................ 46.952-46.962 (1.8485-1.8489)
Main Bearing Journal O.D (Wear Limit), mm (in) ................ 46.91 (1.847)
Main Bearing Clearance, mm (in) ................ 0.15 (0.0059)
Main Bearing I.D (Std), mm (in) ................ 47.00-47.045 (1.850-1.852)
Main Bearing I.D (Wear Limit), mm (in) ................ 47.10 (1.8541)

Cylinder Head (Max Out of Flatness), mm (in) ................ 0.05 (0.002)
Valve Clearance (Cold), mm (in) ................ 0.20 (0.008)
Intake Valve Seat Width (Std), mm (in) ................ 1.36-1.53 (0.054-0.060)
Intake Valve Seat Width (Wear Limit), mm (in) ................ 1.98 (0.078)
Exhaust Valve Seat Width (Std), mm (in) ................ 1.66-1.87 (0.065-0.074)
Exhaust Valve Seat Width (Wear Limit), mm (in) ................ 2.27 (0.089)
Intake and Exhaust Valves Faces, mm (in) ................ 0.51 (0.020)
Exhaust Valve Face Angle, deg ................ 45
Intake Valve Face Angle, deg ................ 30
Valve Stem O.D (Std), mm (in) ................ 6.94-6.96 (0.2732-0.2740)
Valve Stem O.D (Wear Limit), mm (in) ................ 6.90 (0.2717)
Valve Guide I.D (Maximum Clearance), mm (in) ................ 0.20 (0.008)
Valve Guide I.D (Std), mm (in) ................ 7.00-7.02 (0.275-0.276)
Valve Guide I.D (Wear Limit), mm (in) ................ 7.08 (0.279)
Valve Springs Free Length, mm (in) ................ 42.00 (1.654)
Exhaust Valve Seat Angle, deg ................ 45
Intake Valve Seat Angle, deg ................ 30
Camshaft End Play, mm (in) ................ 0.05-0.20 (0.0020-0.0079)
Cam Lobe Height, mm (in) ................ 38.635-38.765 (1.521-1.526)
Camshaft Journal O.D (Gear), mm (in) ................ 44.92-44.95 (1.769-1.770)
Camshaft Journal O.D (Flywheel), mm (in) ................ 44.92-44.95 (1.769-1.770)
Camshaft Journal O.D (Center), mm (in) ................ 44.91-44.94 (1.768-1.769)
Camshaft Bushing I.D, mm (in) ................ 44.990-45.055 (1.771-1.744)
Camshaft Bushing Clearance, mm (in) ................ 0.20 (0.0078)
Camshaft Bore I.D, mm (in) ................ 45.00-45.025 (1.772-1.773)
Rocker Arm Shaft O.D (Std), mm (in) ................ 15.97-15.98 (0.6286-0.6293)
Rocker Arm Shaft O.D (Wear Limit), mm (in) ................ 15.95 (0.6280)
Rocker Arm and Shaft Support Clearance, mm (in) ................ 0.13 (0.005)
Rocker Arm and Shaft Support I.D (Std), mm (in) ................ 16.00-16.02 (0.630-0.631)
Rocker Arm and Shaft Support I.D (Wear Limit), mm (in) ................ 16.09 (0.633)

Piston O.D (Std), mm (in) ................ 77.895-77.925 (3.067-3.068)
Piston O.D (Wear Limit), mm (in) ................ 77.81 (3.063)
Piston O.D (0.25 mm Oversize), mm (in) ................ 78.15-78.18 (3.076-3.077)
Piston O.D (0.50 mm Oversize), mm (in) ................ 78.40-78.42 (3.086-3.087)
Piston Pin O.D (Std), mm (in) ................ 22.991-23.00 (0.905-0.906)
Piston Pin O.D (Wear Limit), mm (in) ................ 22.90 (0.902)
Piston Pin Bore Clearance, mm (in) ................ 0.045 (0.0018)
Piston Pin Bore I.D (Std), mm (in) ................ 23.00-23.009 (0.9055-0.9059)
Piston Pin Bore I.D (Wear Limit), mm (in) ................ 23.02 (0.906)
Piston Pin Bushing Clearance, mm (in) ................ 0.110 (0.0043)
Piston Pin Bushing I.D (Std), mm (in) ................ 23.025-23.038 (0.9065-0.9070)
Piston Pin Bushing I.D (Wear Limit), mm (in) ................ 23.10 (0.909)
Top Ring Groove Clearance, mm (in) ................ 0.075-0.105 (0.0030-0.0041)
Second Ring Groove Clearance, mm (in) ................ 0.035-0.070 (0.0014-0.0028)
Oil Ring Groove Clearance, mm (in) ................ 0.030-0.060 (0.0012-0.0024)
Top Ring End Gap, mm (in) ................ 0.25-0.40 (0.010-0.016)
Second Ring End Gap, mm (in) ................ 0.25-0.40 (0.010-0.016)
Oil Ring End Gap, mm (in) ................ 0.20-0.40 (0.008-0.016)

Injection Pump Timing, deg ................ 16±1, BTDC
Fuel Injection Nozzle Pressure, kPa (psi) ................ 19600±480 (2843±70)
Fuel Supply Pump Pressure, kPa (psi) ................ 29 (4.3)
Cylinder bore inside diameter, mm (in) ................ 78.00-78.03 (3.071-3.072)
Cylinder head (max out of flatness), mm (in) ................ 0.05 (0.002)
Intake valve clearance (Cold), mm (in) ................ 0.20 (0.008)
Exhaust valve clearance (Cold), mm (in) ................ 0.20 (0.008)
Cylinder compression, kPa (psi) ................ 2448 (355)
Engine oil pressure, kPa (psi) ................ 262-345 (38-50)
Fan belt tension, N (lbf) ................ 98 (22)
Fan belt deflection, mm (in) ................ 10-15 (0.40-0.60)
Engine oil type ................ SAE 10W-30, 15W-40, 5W-30
API service classification ................ CE or CD
Engine oil capacity, L (qts) ................ 4.0 (4.25)
Oil filter part number ................ 129150-35150
Air filter part number ................ 129100-55650
Fuel filter part number ................ 121120-12901

Check Battery Conditions ................ Every 50 hours
Check and Adjust Fan Belt ................ Every 100 hours
Change Engine Oil ................ Every 200 hours
Replace Engine Oil Filter ................ Every 200 hours
Replace Fuel Filter ................ Every 200 hours
Clean Air Filter ................ Every 200 hours
Clean Radiator Fins ................ Every 200 hours
Replace Air Cleaner Element ................ Every 500 hours
Adjust Valve Clearance ................ Every 500 hours
Inspect Fuel Injectors ................ Every 500 hours
Flush and Refill Cooling System ................ Every 1000 hours

Rocker Arm Cover, Nm (lb-ft) ................ 18 (13.3)
Rocker Arm Assembly, Nm (lb-ft) ................ 26 (19.3)
Cylinder Head, Nm (lb-ft) ................ 69 (51)
Exhaust Manifold, Nm (lb-ft) ................ 26 (19.3)
Intake Manifold, Nm (lb-ft) ................ 26 (19.3)
Piston and Connecting Rod, Nm (lb-ft) ................ 39 (29)
Flywheel Housing Screw, Nm (lb-ft) ................ 49 (36)
Crankshaft Rear Oil Seal, Nm (lb-ft) ................ 26 (19.3)
Crankshaft and Main Bearings, Nm (lb-ft) ................ 79 (58)
Flywheel, Nm (lb-ft) ................ 83 (61)
Flywheel Housing, Nm (lb-ft) ................ 49 (36)
Camshaft, Nm (lb-ft) ................ 26 (19.3)
Timing Gear Cover, Nm (lb-ft) ................ 26 (19.3)
Crankcase Housing, Nm (lb-ft) ................ 22 (16.3)
Crankshaft Pulley, Nm (lb-ft) ................ 115 (85)
Oil Pump, Nm (lb-ft) ................ 25 (18)
Thermostat Cover, Nm (lb-ft) ................ 20 (14.8)
Water Pump, Nm (lb-ft) ................ 26 (19.3)
Fan Mounting, Nm (lb-ft) ................ 11 (8.1)
Fuel Injection Pump, Nm (lb-ft) ................ 26 (19.3)
Fuel Injection Nozzles, Nm (lb-ft) ................ 43 (31)

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Gasoline and Diesel Engines Technical Data