Mitsubishi S4Q, S4Q2 Diesel Engine Service Manual (tp6839)

These Mitsubishi S4Q and S4Q2 diesels usually live in forklifts, generators, and compact equipment working in dusty yards, warehouses, or construction sites. This service manual is what I’d keep open when I have to trace a hard-start, an overheating issue, or an oil leak back to the real cause instead of just throwing parts at it. For example, if an engine is smoking and down on power, I’d use this book to follow the fuel and air systems step by step, verify adjustments, and confirm which component has actually failed before I pull anything off.

Applications & Use Cases

Track down no-start or hard-start issues by following the diagnostic logic for fuel, air, and compression checks.
Isolate overheating problems by tracing coolant flow, inspecting components in order, and verifying adjustments.
Disassemble and reassemble the engine in a clean sequence so you don’t miss seals, shims, or timing marks.
Confirm wear limits and clearances conceptually so you know when a part is truly beyond service, not just dirty.
Align and time components after major work so the engine fires correctly and runs smoothly.

FAQ

Q: Can I use this manual on a tablet at the machine?

A: Yes, it’s practical to keep it open on a tablet or laptop so you can zoom diagrams and follow steps right at the engine.

Q: Is it worth printing parts of this manual?

A: Many techs print the pages they use most—like procedures they’ll get greasy—so they can mark notes and keep the original file clean.

Safety Note

Always lock out the machine, disable starting, and let the engine cool before opening any system or removing components.

📘 Show Index

Mitsubishi S4Q, S4Q2 Diesel Index:

General
External view
System flow diagrams
Engine serial number location
Main specifications
Tips on disassembling and reassembling
1
Service data Maintenance service data
Tightening torque table 2
Service tools General tools
Special tool 3
Determination of overhaul Determining overhaul timing
Testing compression pressure 4
Disassembly of basic engine
Disassembling and inspecting cylinder head and valve mechanism
Disassembling and inspecting flywheel
Disassembling and inspecting timing gear, camshaft and oil pan
Disassembling and inspecting piston, connecting rod, crankshaft and crankcase
5
Inspection and repair of basic engine
Inspecting and repairing cylinder head and valve mechanism
Inspecting and repairing flywheel
Inspecting and repairing timing gear, camshaft and oil pan
Inspecting and repairing piston, connecting rod, crankshaft and crankcase
6
Reassembly of basic engine
Reassembling piston, connecting rod, crankshaft and crankcase
Reassembling timing gear, camshaft and oil pan
Reassembling flywheel
Reassembling cylinder head and valve mechanism
7
Fuel system
Removing fuel system
Disassembling, inspecting and reassembling fuel system
Installing fuel system
8
Lubrication system
Removing lubrication system
Disassembling, inspecting and reassembling lubrication system
Installing lubrication system
9
Cooling system
Removing cooling system
Disassembling, inspecting and reassembling cooling system
Installing cooling system
10
Inlet and exhaust system
Removing inlet and exhaust system
Inspecting inlet and exhaust system
Installing inlet and exhaust system
11
Electrical system
Removing electrical system
Disassembling, inspecting and reassembling electrical system
Installing electrical system
12
Adjustment and operation
Adjusting engine
Break-in operation
Performance test (JIS standard)
13