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Isuzu 3LD1 Engine

The Isuzu 3LD1 is a compact, vertical, in-line three-cylinder, four-cycle, water-cooled industrial diesel engine. It features an Overhead Valve (OHV) valvetrain layout and utilizes an indirect injection system with a swirl combustion chamber design. Known for its high reliability, efficient power density, and smooth operation, this engine is commonly deployed in medium-sized agricultural machinery, light commercial equipment, mini-excavators (such as the Bobcat 331), and compact mobile generators.

The valvetrain consists of an overhead valve (OHV) setup with the camshaft positioned in the cylinder block, operating the valves via pushrods and rocker arms. The camshaft is driven via a gear-train system directly linked to the crankshaft timing marks, eliminating the need for a timing belt or timing chain. Bore: 83.1 mm (3.27 in). Stroke: 92.0 mm (3.62 in). Total Displacement: 1.496 liters (91.3 cubic inches). Compression Ratio: 22:1.

The fuel system uses a high-pressure Bosch PFR-type mini injection pump managed by a responsive mechanical governor. Fuel is atomized into the swirl combustion chamber through throttle-type injection nozzles. Cold-weather starting is supported by a fast-heating QOS-III glow plug preheating system integrated directly into each cylinder head chamber.

The lubrication circuit utilizes a forced-feed pressure system driven by a trochoid-type oil pump. It filters oil through a full-flow cartridge element located on the lower right side of the cylinder block. Engine temperature is regulated by a pressurized forced water circulation system. A centrifugal vane-type water pump is driven by a vee-belt from the crankshaft pulley. The layout features a side-oriented water outlet with a 7-blade suction fan.

General Technical Data

Engine Specifications

Engine Model ............... Isuzu 3LD1
Engine Type ............... 4-cycle vertical inline 3-cylinder overhead valve liquid-cooled diesel
Number of Cylinders ............... 3
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 3.27 (83.1)
Engine Stroke, in (mm) ............... 3.62 (92.0)
Displacement, cu.in (L) ............... 91.3 (1.496)
Gross Intermittent Power, hp (kW) ............... 33.3 (24.8) at 3000 rpm
Net Continuous Power, hp (kW) ............... 29.3 (21.8) at 3000 rpm
Maximum Torque ............... 70.3 lb-ft (97.0 Nm) at 1800 rpm
Minimum Idle Speed ............... 800-900 rpm
Maximum No-Load Speed ............... 3200 rpm
Aspiration Type ............... Naturally Aspirated
Combustion System ............... Indirect Injection
Compression Ratio ............... 22.0:1
Firing Order ............... 1-3-2
Rotation Direction ............... Counterclockwise viewed from flywheel
Cylinder Block Material ............... Cast iron
Cylinder Head Material ............... Cast iron
Combustion Chamber Type ............... Direct injection
Valves per Cylinder ............... 2
Lubrication System ............... Full-pressure fed
Oil Pump Type ............... Trochoid type driven by crankshaft gear
Oil Filter Type ............... Full-flow spin-on cartridge
Cooling System ............... Liquid-cooled pressurized forced circulation
Water Pump Type ............... Belt-driven centrifugal vane type
Air Cleaner Type ............... Dry element dual-stage
Starting System ............... Electric starter motor
Electrical System ............... 12V DC
Alternator Capacity, A ............... 20A

Fuel System

Injection Pump Type ............... Bosch PFR type flange-mounted mini pump
Injection Pump Manufacturer ............... Zexel
Injection Nozzle Type ............... Throttle type
Nozzle Injection Starting Pressure, psi (MPa) ............... 1920 (13.2)
Fuel Injection Timing, deg BTDC ............... 19.0
Governor Type ............... Mechanical variable speed control
Fuel Feed Pump Type ............... Mechanical diaphragm type
Fuel Filter Type ............... Cartridge spin-on element with water sedimenter
Recommended Fuel Type ............... Diesel fuel SAE 2D Type
Fuel Return Pipe Diameter, in (mm) ............... 0.16 (4.0)
Fuel Inlet Pipe Diameter, in (mm) ............... 0.31 (8.0)
Maximum Fuel Pump Suction Head, in (mm) ............... 39.37 (1000.0)

Dimensions and Weight

Overall Length, in (mm) ............... 21.1 (535)
Overall Width, in (mm) ............... 18.7 (475)
Overall Height, in (mm) ............... 23.2 (590)
Dry Weight, lbs (kg) ............... 290 (132)

Maintenance Data

Service Information

Compression Pressure, Standard, psi (MPa) ............... 441.0 (3.04)
Compression Pressure, Minimum Limit, psi (MPa) ............... 341.0 (2.35)
Compression Variance Between Cylinders, psi (MPa) ............... 28.4 (0.20)
Oil Pressure at Rated Speed, psi (kPa) ............... 42.6-64.0 (294.0-441.0)
Oil Pressure at Idle Speed, psi (kPa) ............... 14.2 (98.0)
Thermostat Opening Temperature, F (C) ............... 170.0 (76.5)
Thermostat Full Open Temperature, F (C) ............... 194.0 (90.0)
Intake Valve Clearance, Cold, in (mm) ............... 0.0078 (0.20)
Exhaust Valve Clearance, Cold, in (mm) ............... 0.0078 (0.20)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30, 10W-30, or SAE 15W-40
API Service Classifications ......................... CC, CD, or CE
Engine Oil Capacity, Pan Only, qts (L) ............... 6.66 (6.3)
Engine Oil Capacity with Filter, qts (L) ............... 7.19 (6.8)
Coolant Capacity, Block and Head Only, qts (L) ............... 2.64 (2.5)

Service Intervals

Change oil and filter ............... Every 250 hours
Inspect air cleaner ............... Every 100 hours
Replace air cleaner ............... Every 500 hours
Replace fuel filter ............... Every 500 hours
Valve clearance adjustment ............... Every 1000 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 Diameter, Standard, in (mm) ............... 3.2716-3.2728 (83.100-83.130)
Cylinder Bore Diameter, Rebuild Limit, in (mm) ............... 3.2795 (83.300)
Connecting Rod Small End Bushing I.D, in (mm) ............... 0.9846-0.9854 (25.010-25.030)
Connecting Rod Big End Thrust Clearance, in (mm) ............... 0.0059-0.0138 (0.150-0.350)
Connecting Rod Bearing Oil Clearance, in (mm) ............... 0.0011-0.0024 (0.029-0.061)
Crankshaft Main Journal Outside Diameter, in (mm) ............... 2.0425-2.0433 (51.880-51.900)
Crankpin Journal Outside Diameter, in (mm) ............... 1.8457-1.8465 (46.880-46.900)
Crankshaft Main Journal Bearing Clearance, in (mm) ............... 0.0011-0.0027 (0.029-0.069)
Crankshaft Runout Standard, in (mm) ............... 0.0008 (0.020)
Crankshaft Center Journal Thrust Clearance, in (mm) ............... 0.0024-0.0094 (0.060-0.240)
Piston Outside Diameter, in (mm) ............... 3.2693-3.2705 (83.040-83.070)
Piston to Cylinder Bore Clearance, in (mm) ............... 0.0012-0.0035 (0.030-0.090)
Piston Pin Bore Inside Diameter, in (mm) ............... 0.9843-0.9846 (25.002-25.011)
Piston Pin Outside Diameter, in (mm) ............... 0.9839-0.9843 (24.991-25.000)
Piston Pin to Piston Pin Bore Clearance, in (mm) ............... 0.0001-0.0008 (0.002-0.020)
Piston Pin to Bushing Clearance, in (mm) ............... 0.0004-0.0015 (0.010-0.039)
Top Piston Ring Groove Width, in (mm) ............... 0.0811-0.0823 (2.060-2.090)
Second Ring Groove Width, in (mm) ............... 0.0606-0.0614 (1.540-1.560)
Oil Ring Groove Width, in (mm) ............... 0.1583-0.1591 (4.020-4.040)
Top Ring Side Clearance, in (mm) ............... 0.0024-0.0039 (0.060-0.100)
Second Ring Side Clearance, in (mm) ............... 0.0020-0.0035 (0.050-0.090)
Oil Ring Side Clearance, in (mm) ............... 0.0008-0.0024 (0.020-0.060)
Top Ring End Gap, in (mm) ............... 0.0079-0.0138 (0.200-0.350)
Second Ring End Gap, in (mm) ............... 0.0079-0.0138 (0.200-0.350)
Oil Ring End Gap, in (mm) ............... 0.0079-0.0157 (0.200-0.400)
Cylinder Head Distortion, Standard, in (mm) ............... 0.0020 (0.05)
Valve Guide Inside Diameter, in (mm) ............... 0.2756-0.2762 (7.000-7.015)
Intake Valve Stem Outside Diameter, in (mm) ............... 0.2732-0.2740 (6.940-6.960)
Exhaust Valve Stem Outside Diameter, in (mm) ............... 0.2724-0.2732 (6.920-6.940)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0016-0.0029 (0.040-0.075)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0024-0.0037 (0.060-0.095)
Valve Thickness, Standard, in (mm) ............... 0.0394 (1.00)
Valve Thickness, Rebuild Limit, in (mm) ............... 0.0276 (0.70)
Valve Seat Contact Width, Standard, in (mm) ............... 0.0472 (1.20)
Valve Seat Contact Width, Rebuild Limit, in (mm) ............... 0.0787 (2.00)
Valve Seat Angle, deg ............... 45
Valve Spring Free Length, Standard, in (mm) ............... 1.4843 (37.70)
Valve Spring Free Length, Rebuild Limit, in (mm) ............... 1.4252 (36.20)
Camshaft Journal Outside Diameter (Front), in (mm) ............... 1.5717-1.5724 (39.920-39.940)
Camshaft Journal Outside Diameter (Center), in (mm) ............... 1.5638-1.5646 (39.720-39.740)
Camshaft Journal Outside Diameter (Rear), in (mm) ............... 1.5559-1.5567 (39.520-39.540)
Camshaft Journal Oil Clearance, in (mm) ............... 0.0016-0.0035 (0.040-0.090)
Cam Lobe Height (Intake), in (mm) ............... 1.3035 (33.11)
Cam Lobe Height (Exhaust), in (mm) ............... 1.3035 (33.11)
Camshaft Runout Limit, in (mm) ............... 0.0020 (0.050)
Tappet Outside Diameter, in (mm) ............... 0.8244-0.8252 (20.940-20.960)
Tappet to Cylinder Block Clearance, in (mm) ............... 0.0016-0.0030 (0.040-0.075)
Rocker Arm Shaft Outside Diameter, in (mm) ............... 0.4713-0.4720 (11.970-11.990)
Rocker Arm Bushing Inside Diameter, in (mm) ............... 0.4724-0.4736 (12.000-12.030)
Crankshaft Gear to Idler Gear Backlash, in (mm) ............... 0.0012-0.0047 (0.030-0.120)
Camshaft Gear to Idler Gear Backlash, in (mm) ............... 0.0012-0.0047 (0.030-0.120)
Injection Pump Gear to Idler Gear Backlash, in (mm) ............... 0.0012-0.0047 (0.030-0.120)

Tightening Torques

Cylinder Head Bolt (Stage 1), lb-ft (Nm) ............... 22.1 (30.0)
Cylinder Head Bolt (Stage 2), lb-ft (Nm) ............... 44.3 (60.0)
Connecting Rod Cap Bolt, lb-ft (Nm) ............... 39.1-44.9 (53.0-61.0)
Main Bearing Cap Bolt, lb-ft (Nm) ............... 57.9-65.1 (78.5-88.3)
Flywheel Bolt, lb-ft (Nm) ............... 57.9-65.1 (78.5-88.3)
Crankshaft Pulley Center Bolt, lb-ft (Nm) ............... 65.1-72.3 (88.3-98.1)
Camshaft Thrust Plate Bolt, lb-ft (Nm) ............... 13.7-21.0 (19.0-28.0)
Idler Gear Shaft Bolt, lb-ft (Nm) ............... 13.7-21.0 (19.0-28.0)
Timing Gear Case Bolt, lb-ft (Nm) ............... 13.7-21.0 (19.0-28.0)
Timing Gear Case Cover Bolt, lb-ft (Nm) ............... 5.8-8.7 (8.0-12.0)
Cylinder Head Cover Nut, lb-ft (Nm) ............... 1.4-3.6 (2.0-5.0)
Rocker Arm Shaft Bracket Bolt, lb-ft (Nm) ............... 13.7-21.0 (19.0-28.0)
Oil Pan Drain Plug, lb-ft (Nm) ............... 36.2-43.4 (49.0-59.0)
Oil Pan Securing Bolt, lb-ft (Nm) ............... 5.8-8.7 (8.0-12.0)
Oil Pump Assembly Fixing Bolt, lb-ft (Nm) ............... 13.7-21.0 (19.0-28.0)
Water Pump Assembly Bolt, lb-ft (Nm) ............... 13.7-21.0 (19.0-28.0)
Cooling Fan Nut, lb-ft (Nm) ............... 5.8-8.7 (8.0-12.0)
Thermostat Housing Bolt, lb-ft (Nm) ............... 13.7-21.0 (19.0-28.0)
Inlet Manifold Bolt, lb-ft (Nm) ............... 13.7-21.0 (19.0-28.0)
Exhaust Manifold Bolt, lb-ft (Nm) ............... 13.7-21.0 (19.0-28.0)
Exhaust Pipe Stud Nut, lb-ft (Nm) ............... 17.4-24.6 (23.5-33.3)
Injection Pump Fixing Nut, lb-ft (Nm) ............... 13.7-21.0 (19.0-28.0)
Injection Pump Delivery Valve Holder, lb-ft (Nm) ............... 25.3-28.9 (34.3-39.2)
Injection Nozzle Retaining Nut, lb-ft (Nm) ............... 25.3-32.5 (34.3-44.1)
High Pressure Fuel Line Leak-Off Pipe Nut, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Glow Plug, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Starter Motor Mounting Bolt, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Alternator Mounting Bolt Main Pivot, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Alternator Adjusting Plate Lock Bolt, lb-ft (Nm) ............... 13.7-21.0 (19.0-28.0)
Oil Pressure Switch, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Coolant Temperature Sensor, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Flywheel Housing Bolt, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)

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• Isuzu Engines Specs
  
• Isuzu 3KC1 Specs
  
• Isuzu 3KC2 Specs
  
• Isuzu 3KR1 Specs
  
• Isuzu 3KR2 Specs
  
• Isuzu 3LB1 Specs
  
• Isuzu 3LD2 Specs
  

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