Kubota D1503

Kubota D1503The Kubota D1503-M is a 1.5 L (1,499 cc, 91.44 cu·in) straight-three, water-cooled naturally aspirated vertical diesel engine manufactured by Kubota.

The Kubota D1503-M-E engine has a spherical type сombustion сhamber (E-TVCS), the Bosch mini fuel injection pump. The cylinder bore and the piston stroke are 83.0 mm (3.27) in and 92.4 mm (3.64 in), respectively. The compression ratio rating is 23.0:1.

The D1503-M-E diesel engine produced 31.0 PS (22.8 KW; 30.5 HP) at 2,800 rpm of net horsepower.

The breakdown of the engine code is as follows:

  • D – 3-cylinders
  • 15 – Approximate displacement 1500 cc

General information

Engine Specifications
Engine code D1503-M-E
Layout Straight-3, vertical diesel engine
Fuel type Diesel fuel No.2-D
Displacement 1.5 L, 1,499 cm3 (91.44 cu in)
Fuel injection pump Bosch mini fuel injection pump
Fuel nozzle
Starting system Electric starting with 12V (1.4 kW) starter
Starting support device Glow plug
Governor Centrifugal mechanical governor
Power adder None
Max. Horsepower Net (intermittent): 31.0 PS (22.8 KW; 30.5 HP) at 2,800 rpm
Net (continuous): 27.0 PS (19.8 KW; 26.5 HP) at 2,800 rpm
Torque output
Firing order 1-2-3
Dimensions (L x W x H): 572 x 507 x 643 mm (22.5 x 20.0 x 25.3 in)
Weight 148.0 kg (326.0 lbs)

Cylinder block

Cylinder block
Compression ratio: 23.0:1
Cylinder bore: 83.0 mm (3.27 in)
Piston stroke: 92.4 mm (3.64 in)
Number of piston rings (compression / oil): 2 / 1
Cylinder inner diameter: 83.000-83.022 mm (3.2677-3.2686 in)
Piston skirt diameter
Piston ring side clearance: Second 0.093-0.120 mm (0.0037-0.0047 in)
Oil 0.020-0.060 mm (0.0008-0.0023 in)
Piston ring end gap: Top 0.200-0.350 mm (0.0080-0.0138 in)
Second 0.300-0.450 mm (0.0118-0.0177 in)
Oil 0.250-0.450 mm (0.0099-0.0177 in)
Piston pin outer diameter 23.002-23.011 mm (0.9056-0.9059 in)
Crankshaft main journal diameter: S/n below 3R9999: 51.921-51.940 mm (2.0441-2.0449 in)
S/n above 3S0001: 59.921-59.940 mm (2.3590-2.3598 in)
Crankpin diameter: 46.959-46.975 mm (1.8487-1.8494 in)

Cylinder head

Cylinder head
Valve Arrangement: OHV, gear drive
Valves: 6 (2 valves per cylinder)
Valve timing: INTAKE
Valve seat width: INTAKE 2.120 mm (0.0835 in)
EXHAUST 2.120 mm (0.0835 in)
Valve stem diameter: INTAKE 7.960-7.975 mm (0.3134-0.3140 in)
EXHAUST 7.960-7.975 mm (0.3134-0.3140 in)
Valve spring free length: INTAKE 41.7-42.2 mm (1.6417-1.6614 in)
EXHAUST 41.7-42.2 mm (1.6417-1.6614 in)
Camshaft cam height: INTAKE 33.900 mm (1.3346 in)
EXHAUST 33.900 mm (1.3346 in)
Camshaft journal diameter: 39.934-39.950 mm (1.5722-1.5728 in)

Tightening torque

Tightening torque specs
Rocker arm bracket screw: 23.5-27.5 Nm (2.4-2.8 kgf-m, 17.4-20.3 lb-ft)
Cylinder head: 93.1-98.0 Nm (9.5-10.0 kgf-m, 68.7-72.3 lb-ft)
Nozzle holder assembly: 49.0-68.6 Nm (5.0-7.0 kgf-m, 36.2-50.6 lb-ft)
Connecting rod screw: 44.1-49.0 Nm (4.5-5.0 kgf-m, 32.5-36.2 lb-ft)
Flywheel bolts: 98.1-107.9 Nm (10.0-11.0 kgf-m, 72.3-79.6 lb-ft)
Main bearing case screw 1: 46.1-50.9 Nm (4.7-5.2 kgf-m, 34.0-37.6 lb-ft)
Main bearing case screw 2: 68.6-73.5 Nm (7.0-7.5 kgf-m, 50.6-54.2 lb-ft)

Maintenance data

Valve clearance
Intake valve 0.18-0.22 mm (0.0071-0.0087 in)
Exhaust valve 0.18-0.22 mm (0.0071-0.0087 in)
Compression pressure
Standard 36.0-41.0 kgf/cm2 (3.53-4.02 MPa, 512-583 psi)
Oil system
Recommended engine oil CD or CE
SAE Viscosity Number SAE 10W-30, 10W-40
Engine oil capacity Oil pan depth 90.0 mm (3.54 in): 5.6 L (1.5 US gal, 1.2 Imp. gal)
Oil pan depth 124.0 mm (4.88 in): 7.0 L (1.8 US gal, 1.5 Imp. gal)
Fuel system
Injection timing: 17-19° B.T.D.C.
Fuel injection pressure 13.73-14.7 MPa (140-150 kgf/cm2, 1991-2133 psi)
Cooling system
Thermostat’s valve opening temperature: 69.5-72.5°C (157.1-162.5°F)
Temperature at which thermostat completely opens: 85°C (185°F)
Coolant capacity: 5.5 liters (1.5 US gal, 1.2 Imp. gal)
Electrical system
Battery: 12V, 80 Ah
Alternator current output: 35A/14V at 4,000 rpm
Alternator brush Length (std/min): 10.5 mm (0.4130 in) / 8.4 mm (0.3310 in)
Glow plug resistance: Approx 0.8 Ω
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