Got a 4LE2 industrial diesel that won't cooperate? This 211-page Isuzu workshop manual (OEM #4LE2IT4-WE-0991) covers AU-4LE2 and BV-4LE2 variants from top end to oil pump. One hundred pages of step-by-step procedures span engine mechanical, fuel, cooling, electrical, exhaust, and lubrication systems. Wiring diagrams detail charging circuits for both 12V and 24V generator setups, and 25 exploded views place every bolt, gasket, and seal in context. Nine troubleshooting flowcharts help you isolate faults before pulling parts. Cylinder head bolts torque to 83.4–93.2 N·m with a 60°–90° angle turn; oil pressure should read 147 kPa at 1,000 RPM before final assembly. Bookmarked and searchable, this PDF works on your phone right at the machine. Get the specs, get the procedure, get it running.
What's Inside This Isuzu AU-4LE2, BV-4LE2 Manual
| System | Pages | Key Topics |
|---|---|---|
| Engine Mechanical | 38-138 | Isuzu Diesel Engine, Engine Accessories, Engine Exterior Equipment, Rocker Arm Shaft |
| Cooling System | 139-148 | Service Precautions, Function Check, Water Pump, Thermostat |
| Fuel System | 149-162 | Service Precautions, Explanations On Functions And Operation, Governor, Components |
| Electrical System | 163-193 | Charging System, Generator (24V-30A), Generator (24V-50A), Generator (12V-20A) |
| Exhaust System | 194-199 | Egr Control, Connector Pin Layout, Boost Pressure Sensor Circuit Diagram, Inspection |
| Lubrication System | 200-204 | Service Precautions, Function Check, Oil Filter, Oil Pump |
| Intake System | 205-207 | - |
| Preheating System | 208-211 | Explanations On Functions And Operation |
Isuzu AU-4LE2, BV-4LE2 Specifications
| Specification | Value | Page |
|---|---|---|
| All Models | ||
| Generator mounting bolt tightening torque (M10) | 41.2 — 55.0 N·m {4.2 — 5.6 kgf·m/ 30.4 — 40.6 lb·ft} | p. 167 |
| Cylinder head bolt tightening torque (M12 × 1.5) | 83.4 — 93.2 N·m {8.5 — 9.5/ 61.5 — 68.7} → 60° — 90° | p. 26 |
| Boost pressure sensor backup control (open circuit) | Control as the boost pressure is 15 kPa {2.2 psi} or more. | p. 197 |
| Lubrication oil pressure (at 1,000 rpm) | 147 {21} kPa {psi} | p. 36 |
| Thermostat working start temperature (at barometric pressure) | 82°C {180°F} | p. 32 |
| Compression Pressure (Standard) | 3.04 MPa | p. 25 |
| Compression Pressure (Service Limit) | 2.5 MPa | p. 25 |
| Cylinder Head Bolt Torque (M12 x 1.5) | 83.4 - 93.2 N·m, then angle tighten 60° - 90° | p. 26 |
| Valve Clearance (Cold) | 0.40 ± 0.05 mm | p. 41 |
| 4LE2X | ||
| Engine Oil Capacity | 9.3 - 12.1 L | p. 15 |
| Fuel Injection Timing (BTDC) | 2° | p. 49 |
| 4LE2N | ||
| Engine Oil Capacity | 5.9 - 8.4 L | p. 15 |
Isuzu AU-4LE2, BV-4LE2 Common Problems This Manual Covers
Isuzu 4LE2 engine cranks but won't start, no combustion after extended cranking
Follow the no-start diagnostic flowchart first. Loosen a high-pressure line fitting and crank briefly to confirm fuel is reaching the injectors. Inspect the glow plug system per the preheating diagnosis on page 209; failed plugs prevent ignition in cold cylinders. Measure compression pressure, which should read 3.04 MPa standard or above the 2.5 MPa service limit per page 25. Low readings across multiple cylinders point to valve or head gasket failure.
Manual Section: Engine Does Not StartEngine overheats during operation, coolant temperature climbs past normal range
Start with the cooling system diagnostic flowchart. Confirm the thermostat opens at 82°C (180°F) per the spec on page 32; a stuck-closed thermostat is the most common culprit. Verify water pump drive belt tension and look for leaks at hose connections and the pump weep hole. If you suspect the head gasket, test for combustion gas in the coolant and confirm cylinder head bolt torque at 83.4 to 93.2 N·m with 60° to 90° angle tightening per page 26.
Manual Section: Overheating and Exhaust FaultsEngine runs rough, has low power, or produces black smoke. p. 149
Open the fuel system section starting on page 149. Verify injection timing is correct per the procedure on page 43 (2° BTDC for 4LE2X, 3° for 4LE2N). Inspect fuel filters for clogging (page 153) and bleed air from the system per page 46. Test injection nozzles for correct spray pattern and 25.0 MPa second-step pressure as detailed on page 45.
Manual Section: Fuel SystemLow oil pressure warning at idle, gauge reads below normal
Confirm oil level and condition before anything else. Review the lubrication system overview on page 201 for oil flow path. Normal pressure at 1,000 RPM should read 147 kPa (21 psi) per the spec on page 36. Inspect oil pressure sensor wiring for damage or loose connections before condemning internal parts. Pull the oil filter and check for metal debris. If pressure stays low with good oil and a known-good sensor, the oil pump or bearings require further inspection per procedures starting on page 200.
Manual Section: Fluid Pressure and ConsumptionBoost pressure sensor fault codes P0237 or P0238, loss of power under load p. 194
Inspect the boost pressure sensor connector and wiring using the circuit diagram on page 195. Look for corroded pins or backed-out terminals at the sensor plug. On open circuit, the ECU defaults to 15 kPa (2.2 psi) per page 197, which severely limits power. Clean carbon buildup from the sensor port (common with EGR gases). If wiring checks good, replace the sensor and clear codes. Verify turbo operation and check for intake leaks between the turbo outlet and intake manifold.
Manual Section: Exhaust SystemWhite or black exhaust smoke at startup or under load
Use the exhaust fault diagnostic flowchart to isolate the cause. White smoke typically signals coolant entering combustion or incomplete fuel burn; verify valve clearance is within 0.40 ± 0.05 mm cold per page 41, since tight valves cause poor sealing. Black smoke points to over-fueling or restricted air intake; inspect the air filter and intake tract starting on page 205. Confirm injection timing matches the specs on page 49 (2° BTDC for 4LE2X, 3° for 4LE2N).
Manual Section: Overheating and Exhaust FaultsIsuzu AU-4LE2, BV-4LE2 workshop FAQ
What are the replacement specifications for the generator's control component?
The IC regulator controls generator output voltage. During testing, regulated voltage should measure 27.5 to 29.5 V at +25°C (77°F). If readings fall outside that range, replace the regulator. Torque both the B terminal and E terminal to 4.9 to 6.9 N·m (43.4 to 61.1 lb·in).
What are the replacement specifications for the head gasket?
Position the head gasket with the stamped mark facing up. Oil the head bolt threads and seating surfaces before installation. Torque M12 bolts to 83.4 to 93.2 N·m (61.5 to 68.7 lb·ft), then angle-tighten 60° to 90°. Torque M8 bolts to 24.5 to 34.3 N·m (18.1 to 25.3 lb·ft).
What do I get after purchasing this Isuzu AU-4LE2, BV-4LE2 manual?
You receive a 211-page searchable PDF, available for immediate download. Open it on any device, phone included. No shipping, no wait.
Is this Isuzu AU-4LE2, BV-4LE2 Workshop Manual printable?
Yes. The PDF carries no DRM restrictions. Print any page or section you need for shop use with any standard printer.
Does this Isuzu AU-4LE2, BV-4LE2 manual include wiring diagrams?
Yes. This manual includes full electrical wiring diagrams, wire routing, and connector pinouts for the 4LE2 engine.
Document Quality
Native digital PDF with vector text and graphics that stay sharp at any zoom or print size. Exploded-view diagrams, wiring schematics, lubrication flow charts, and spec tables are all cleanly rendered with no scan artifacts or pixelation. No source watermarks. Fully print-ready and well suited for on-screen reference in the shop.
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