Isuzu 3LB1 Specifications
| Engine Model: Isuzu 3LB1 |
| Engine Type: 4-stroke in-line 3-cylinder liquid-cooled diesel |
| Total Displacement: 68.6 cu.in (1.12 L) |
| Rated Engine Power: 25.4 Hp (19 kW) at 3000 rpm |
| Fuel System Type: Indirect injection |
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The Isuzu 3LB1 is a compact, 1.1-liter
industrial diesel engine from Isuzu's L-Series. Produced throughout the
1980s and 1990s, this 3-cylinder power unit is recognized for its
reliability, fuel efficiency, and low noise emission. The engine employs
an indirect injection (IDI) combustion system with a swirl
pre-combustion chamber, enabling smooth operation and reduced combustion
harshness. The naturally aspirated configuration eliminates turbocharger
complexity, making the 3LB1 suitable for applications where maintenance
access is restricted.
Common installations include mini-excavators such as the IHI 28J,
compact wheel loaders, small skid steers, and stationary generator sets.
The vertical inline cylinder arrangement and water-cooled design provide
compact dimensions for tight engine compartments. This engine preceded
the electronically managed 3LB2 series, offering a mechanical fuel
system serviceable with basic tools.
Engine Type: 3-cylinder, 4-cycle, vertical in-line, naturally aspirated
diesel
Displacement: 1.124 L (68.6 cu.in)
Bore x Stroke: 77.4 mm x 79.7 mm (3.05 in x 3.14 in)
Aspiration: Naturally aspirated (no turbocharger)
Combustion System: Indirect injection (IDI)
Compression Ratio: 22:1
Firing Order: 1-3-2
Rotation (from flywheel end): Counter-clockwise
Intermittent Power (SAE J1995): 19.0 kW (25.4 hp) at 3000 rpm
Intermittent Torque (SAE J1995): 70.3 Nm (51.9 lb-ft) at 1800 rpm
Continuous Power (SAE J1995): 16.7 kW (22.4 hp) at 3000 rpm
Continuous Torque (SAE J1995): 61.9 Nm (45.7 lb-ft) at 1800 rpm
Maximum Rated Power (Industrial): 20.6 kW (27.6 hp) at 3450 rpm
Maximum Rated Torque: 67 Nm (49.4 lb-ft) at 1800 rpm
Low Idle Speed: 900-950 rpm
High Idle Speed (no-load, governed): 3650 rpm
Compression Pressure (standard): 3.04 MPa (441 psi) at 250 rpm
Compression Pressure (service limit): 2.55 MPa (370 psi) at 250 rpm
Emission Standard: Pre-regulation (Tier 0 equivalent)
The cylinder block is manufactured from cast iron with an open-deck
design. Three cylinder bores are machined directly into the block
without replaceable liners. The block features a siamese bore
configuration where each bore shares a common wall with the adjacent
cylinder, reducing overall length and increasing rigidity. The crankcase
extends below the crankshaft centerline with a deep skirt design.
Four main bearing bulkheads support the crankshaft, with thrust bearing
position at the center main journal. The water jacket surrounds the
upper portion of each cylinder bore. Cast-in oil galleries supply the
main bearings and camshaft bearings. A side-mounted oil dipstick tube is
cast into the block skirt. The timing gear housing is integrated into
the front face of the block.
The cylinder head is a single-piece cast iron component with an indirect
injection (IDI) combustion chamber for each cylinder. Each chamber is a
spherical swirl-type pre-combustion chamber located off-center within
the cylinder bore. Glow plugs are threaded into each pre-combustion
chamber. The valve train is an overhead valve (OHV) configuration. Each
cylinder receives two valves: one intake and one exhaust, arranged in a
parallel valve layout.
Valves are actuated by pushrods and rocker arms. The camshaft is located
in the cylinder block, not the cylinder head. Valve stem seals are
positive-type on intake valves only. Exhaust valve seats are hardened
for wear resistance. The intake ports produce a directed flow pattern to
promote swirl within the pre-combustion chamber. Valve clearance
adjustment uses a screw-and-locknut arrangement on the rocker arms.
The fuel system is a mechanical indirect injection design. A Zexel
(Bosch license) PFR series inline injection pump mounts to the side of
the injection pump base. This pump is a distributor type with a single
plunger that delivers fuel to each cylinder in firing order sequence.
The injection pump incorporates a mechanical centrifugal governor with
both idle and maximum speed control springs. Fuel lines are steel,
routed individually to each injection nozzle located in the
pre-combustion chamber.
Injection nozzles are pintle type with an opening pressure of 9.8-10.8
MPa (1420-1565 psi). Injection timing is adjusted by changing the
thickness of a shim placed between the injection pump mounting flange
and the pump base. A hand primer lever on the feed pump permits manual
bleeding of air from the system. A fuel filter with an integral water
sediment bowl mounts on the engine side.
The lubrication system uses a gear-type oil pump driven from the
camshaft gear. The pump draws oil through a wire mesh suction strainer
positioned at the bottom of the oil pan. Oil passes through a spin-on
full-flow filter mounted on the engine block. A pressure relief valve in
the oil pump opens at 0.49 MPa (71 psi) to prevent over-pressurization
during cold starts.
The system lacks piston cooling jets due to the natural aspiration and
indirect injection combustion system generating lower thermal loads. Oil
pressure at rated speed measures 0.29-0.49 MPa (42-71 psi). Low oil
pressure warning switch activates a lamp at 0.05 MPa (7 psi). Standard
oil pan capacity is 4.5 L (4.8 qt). Optional deep sump increases
capacity to 6.5 L (6.9 qt) for generator applications operating on
inclines.
The cooling system is pressurized and water-cooled, driven by a
belt-mounted centrifugal water pump. Coolant flows from the radiator
lower hose into the pump, then through the cylinder block water jacket,
upward through the cylinder head, and returns to the radiator top tank.
A wax-pellet thermostat, mounted in a housing on the cylinder head,
begins opening at 71.5°C (161°F) and achieves full opening at 85°C
(185°F).
A bypass circuit permits coolant circulation within the engine when the
thermostat remains closed. Coolant capacity for the engine block and
cylinder head only is 2.2 L (2.3 qt). Total system capacity, including
radiator and hoses, ranges from 3.5 to 4.5 L (3.7-4.8 qt) depending on
the installation. A removable pressure cap relieves excess pressure at
0.9 bar (13 psi). A fan mounted to the water pump pulley draws air
through the radiator core.
Aspiration: Natural aspiration without turbocharger. Air passes through
a dry-type paper filter element with a foam pre-cleaner. An intake
silencer reduces induction noise.
Combustion System: Indirect injection using a swirl pre-combustion
chamber. The chamber volume occupies 50-60% of the total clearance
volume. A glow plug heats the chamber for cold start assistance.
Electrical System: 12 V DC negative ground. Starter motor power rating
is 1.0 kW. Alternator output is 20 A. Glow plugs operate at 12 V with a
maximum current of 8 A per plug. Glow plug controller integrates a timer
relay for 5-15 second activation dependent on coolant temperature.
Starting Aid: Glow plugs in each pre-combustion chamber. A
thermistor-equipped timer relay modulates post-heat for reduced white
smoke after start.
Governor: Mechanical centrifugal governor integral to the injection
pump. Governor droop is 8-12% from no-load to full-load at rated speed.
Length (fan to flywheel housing): 564.5 mm (22.22 in).
Width (overall, exhaust manifold to injection pump): 475 mm (18.70 in).
Height (oil pan rail to rocker cover): 563 mm (22.17 in).
Dry Weight (basic engine, no flywheel, no starter, no alternator): 123
kg (271 lb).
Dry Weight (open power unit with radiator, flywheel, starter,
alternator, air cleaner): 169 kg (372 lb).
Oil Pan Depth (standard sump): 95 mm (3.74 in) from block rail.
Engine Oil Change Interval: 250 hours or 6 months under normal
industrial duty.
Engine Oil Capacity (standard pan, including filter): 4.5 L (4.8 qt).
Engine Oil Capacity (deep sump, including filter): 6.5 L (6.9 qt).
Engine Oil Grade (ambient above 10C): SAE 15W-40, 20W-50, API CD or
higher.
Engine Oil Grade (cold ambient -15-10C): SAE 10W-30 or SAE 10W-40.
Engine Oil Grade (extremely cold below -15C): SAE 5W-30.
Engine Oil Pressure at Rated Speed: 0.29-0.49 MPa (42-71 psi).
Engine Oil Pressure at Low Idle (minimum, hot engine): 0.07 MPa (10
psi).
Coolant Capacity (engine only): 2.2 L (2.3 qt).
Coolant Capacity (system total): 3.5-4.5 L (3.7-4.8 qt).
Coolant Specification: Ethylene glycol base antifreeze.
Thermostat Opening Temperature: 71.5C (161F) start; fully open at 85C
(185F).
Fuel Filter Replacement Interval: 200 hours. Water sediment bowl drain
daily.
Air Filter Service Interval: Clean foam pre-cleaner every 50 hours.
Air Filter Service Interval: Replace paper element every 200 hours.
Valve Clearance (Cold, Intake/Exhaust): 0.25 mm (0.010 in).
Valve Clearance Inspection Interval: 250 hours.
Injection Pump Timing (static): 16-18 deg BTDC at No. 1 cylinder.
Injection Timing Adjustment Shim Range: 0.2-1.2 mm (0.008-0.047 in)
thickness.
Injector Nozzle Opening Pressure: 9.8-10.8 MPa (1420-1565 psi).
Injector Nozzle Replacement Interval: 1200 hours.
Glow Plug Resistance (cold): 0.8-1.0 ohm per plug.
Compression Pressure Variation Between Cylinders: Maximum 0.2 MPa (29
psi).
Drive Belt Tension: Deflection of 10-15 mm (0.39-0.59 in) under 10 kg
(22 lb) force.
Idle Speed Adjustment (low): 900-950 rpm.
Idle Speed Adjustment (high, governed): 3650 rpm no-load.
Cylinder Head Bolts (Stage 1): 30 Nm (22 lb-ft).
Cylinder Head Bolts (Stage 2): 70 Nm (52 lb-ft).
Connecting Rod Cap Bolts: 44 Nm (32 lb-ft)
Main Bearing Cap Bolts (all positions): 74 Nm (55 lb-ft)
Flywheel Bolts (to crankshaft flange): 59 Nm (44 lb-ft)
Flywheel Housing Bolts (to block): 44 Nm (32 lb-ft)
Camshaft Thrust Plate Bolts: 15 Nm (11 lb-ft)
Rocker Arm Shaft Bracket Bolts: 27 Nm (20 lb-ft)
Rocker Arm Adjusting Lock Nut: 12 Nm (9 lb-ft)
Valve Cover Nuts (with rubber gasket): 7 Nm (5 lb-ft)
Injection Pump Mounting Nuts (to pump base): 24 Nm (18 lb-ft)
Injection Pump Gear Nut: 45 Nm (33 lb-ft)
Injection Line Fittings (pump end): 25 Nm (18 lb-ft)
Injection Line Fittings (nozzle end): 25 Nm (18 lb-ft)
Injector Hold-Down Clamp Nut: 22 Nm (16 lb-ft)
Crankshaft Pulley Bolt: 110 Nm (81 lb-ft)
Crankshaft Pulley Bolt (angle method if specified): 70 Nm (52 lb-ft)
Oil Pan Bolts (M8): 10 Nm (7 lb-ft)
Oil Pan Drain Plug: 40 Nm (30 lb-ft)
Oil Filter (spin-on canister): 15 Nm (11 lb-ft)
Water Pump Mounting Bolts: 18 Nm (13 lb-ft)
Thermostat Housing Bolts: 10 Nm (7 lb-ft)
Starter Motor Mounting Bolts (12V): 40 Nm (30 lb-ft)
Alternator Mounting Bolt: 25 Nm (18 lb-ft)
Alternator Pivot Bolt: 45 Nm (33 lb-ft)
Glow Plug (in cylinder head): 20 Nm (15 lb-ft)
Exhaust Manifold Nut: 22 Nm (16 lb-ft)
Intake Manifold Bolt: 20 Nm (15 lb-ft)
Engine Mount Bracket Bolts (to block): 55 Nm (41 lb-ft)
Mini-Excavators: IHI 28J, IHI 30J, IHI 35J. Kubota KH-28, KH-30
(licensed installations). Yanmar B27, B30 compact excavators.
Compact Loaders: Takeuchi TB20, TB25 skid steer loaders. Bobcat 320, 322
with Isuzu engine packages.
Stationary Generator Sets: 10-15 kVA single-phase and three-phase
generators. Standby power ratings from 12 kW to 18 kW at 1500 rpm (50
Hz) or 1800 rpm (60 Hz). Models include Denyo DCA-15, MQ Power GA-15.
Agricultural Equipment: Small rice transplanters. Compact irrigation
pumps with direct-coupled shaft drive.
Industrial Power Units: Hydraulic power packs for lift tables and small
presses. Wood chippers and stump grinders. Concrete vibrator heads and
small compaction plates.
Marine Auxiliary: Sailboat auxiliary generators at 1500 rpm. Small
workboat hydraulic pump drives.
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