Need factory teardown data for your Mitsubishi 4DQ7 or S4S diesel? This 147-page Mitsubishi 4DQ7, S4S Service Manual PDF covers both engine variants powering FD10, FD14, FD15, FD18, FD20, FD25, FD30, and FD35A forklifts. Inside: full disassembly, inspection, and reassembly procedures for the cylinder head, timing gears, pistons, crankshaft, and injection pump, plus troubleshooting charts covering everything from hard starts to abnormal exhaust smoke. You also get maintenance standards, clearance tables, and exploded views for every rebuild step. Torque the injection nozzles to 6 ± 1 kgf·m and pull the connecting rod caps down to 5.5 ± 0.5 kgf·m; the numbers are right there in the tightening torque tables. No more chasing specs through forum threads. Bookmarked PDF opens on any device; grab your tablet, walk to the engine, and start wrenching.
What's Inside This Mitsubishi 4DQ7, S4S Manual
| System | Pages | Key Topics |
|---|---|---|
| Front Matter | 1-3 | Cover Page, Foreword, Table of Contents |
| Specifications | 4-5 | - |
| Sectional Views | 6-20 | 4DQ7 Longitudinal Sectional View, 4DQ7 Transverse Sectional View, S4S Longitudinal Sectional View, S4S Transverse Sectional View, Performance Curves (4DQ7, S4S), Maintenance Standards |
| Maintenance Standards | 21-23 | Electrical System Maintenance Standards (Alternator, Cooling System Thermostat, V-Belt Tension), Tightening Torque, Tightening Torque S4S |
| Sealant Application Data | 24-30 | Tightening Torques for Major Components |
| Cylinder Head and Valve Mechanism | 31-45 | Disassembly, Inspection and Repair, Reassembly, Valve Clearance Inspection and Adjustment |
| Timing Gears, Camshaft and Oil Pan | 46-58 | Timing Gear Disassembly, Camshaft Inspection and Repair, Oil Pan Reassembly |
| Flywheel | 59-64 | Flywheel Disassembly, Flywheel Inspection and Repair, Flywheel Reassembly |
| Piston, Connecting Rods, Crankshaft and Crankcase | 65-82 | Piston and Connecting Rod Inspection, Crankshaft and Crankcase Reassembly |
| Engine Proper | 83-84 | Installing Main Bearings 4DQ7, Installing Pistons, Installing Crankshaft, Installing Main Bearing Caps |
| Oil Pump | 85-97 | Description, Reassembly |
| Oil Filter | 98-110 | Relief Valve, Water Pump, Thermostat, Fuel Filter (Disassembly and Inspection), Injection Nozzles (Disassembly, Inspection and Adjustment) |
| Injection Pump | 111-125 | Removal, Installation, Adjusting Injection Timing, Adjusting the Idling and Maximum Speeds, Starter (Disassembly, Inspection and Repair, Reassembly) |
| Electrical System | 126-131 | Alternator (Disassembly, Inspection), Heater Plugs (Inspection, Replacing Bearings, Holding Brush) |
| Workshop Theory | 132-136 | Suggestions on Disassembly and Reassembly (Oil Seals, O-Rings, Bearings, Lock Plates, Split Pins and Spring Pins), Testing the Compression Pressure |
| Troubleshooting | 137-145 | Troubleshooting Chart 1 (Engine Will Not Start, Engine Lacks Power, Abnormal Exhaust Smoke, Fuel System Complaints), Troubleshooting Chart 2 (Poor Fuel Supply to Injection Pump, Injection Timing, Poor Compression) |
| General Specifications | 146-147 | Engine Proper Specifications, Valve Timing, Starting System, Lubrication System Specifications, Cooling System Specifications, Fuel System Specifications, Injection Nozzles |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Oil drain plug | 4 ± 0.5 kgf·m | p. 16 |
| Oil filter | 1.5 to 2.0 kgf·m | p. 16 |
| Injection nozzle | 6 ± 1 kgf·m | p. 16 |
| Injection pipe nut | 2.5 to 3.5 kgf·m | p. 16 |
| Connecting rod cap | 5.5 ± 0.5 kgf·m | p. 16 |
| Water drain plug | 4.5 ± 0.5 kgf·m | p. 17 |
| Crankpin diameter (4DQ7) assembly standard | 57.945 to 57.965 (2.28129 to 2.28208) mm (in.) | p. 71 |
| Cylinder Head Tightening Torque | 118 ± 5 N·m | p. 22 |
Mitsubishi 4DQ7, S4S Common Problems This Manual Covers
Mitsubishi 4DQ7 diesel cranks over strong but won't start, no exhaust smoke while cranking
Check fuel delivery first: crack an injection pipe nut and crank; no fuel means a supply problem, not compression. Bleed the system, then run the no-start chart on page 138. If you pulled nozzles to test spray, torque them back to 6 ± 1 kgf·m (59 ± 10 N·m) so they seal.
Manual Section: Engine General Troubleshooting (No-start, Power, Smoke, Noise, Stalling, Speed, Consumption, Contamination, Warning Lamps) p. 138Loud knocking from the valve cover and hard starting after valve work or high hours
Pull the valve cover and check valve clearance on every cylinder with the engine cold, following the inspection and adjustment procedure starting. Inspect each tappet face for cracks, pitting, and poor seating; replace any that rock in their bores. While the cover is off, verify cylinder head bolts hold 118 ± 5 N·m.
Manual Section: Cylinder Head and Valve Mechanism (Disassembly, Repair, Reassembly, Valve Clearance Inspection and Adjustment)Engine overheats under load, coolant boils out of the radiator within an hour
Shut it down and let it cool; never add coolant to an overheated engine. Check fan belt deflection against the 12 mm (0.47 in) limit and tension or replace the belt if it exceeds that. Blow out clogged radiator fins with compressed air, then verify the thermostat opens before condemning the water pump.
Manual Section: Cooling System TroubleshootingLow oil pressure at idle, metallic glitter showing up in the drained engine oil
Drain the oil and cut the filter open; bronze or silver flake points to bearing failure, not thin oil. Drop the pan, pull the connecting rod caps, and inspect each shell for wiping, scratching, and corrosion per page 75. Torque rod caps to 5.5 ± 0.5 kgf·m on reassembly with fresh bearings.
Manual Section: Jammed Moving Parts Troubleshooting p. 75Engine lacks power and hunts at idle, fuel filter element keeps clogging with black sludge
Replace the fuel filter element and drain the water separator, then bleed air all the way to the injection pump. Chase the poor-supply and injection-quantity checks on page 142. Crack each injection pipe at the nozzle while running to find a dead cylinder; retorque pipe nuts to 2.5 to 3.5 kgf·m when done.
Manual Section: Fuel System Troubleshooting p. 142Frequently Asked Questions
What fluids and capacities does this machine require?
The machine requires Grade No. 2-D diesel fuel. For the 4DQ7 model, the engine oil capacity is 6.7 liters (1.8 U.S. gal) and the cooling system capacity is 4.1 liters (1.1 U.S. gal). For the S4S model, the engine oil capacity is 9 liters (2.4 U.S. gal) and the cooling system capacity is 5.5 liters (1.5 U.S. gal). p. 3
How to troubleshoot engine won't start?
To troubleshoot an engine that won't start, refer to the troubleshooting chart. Possible causes include insufficient fuel supply to the injection pump, clogged fuel lines, a defective starter switch, or a battery voltage drop. The chart provides specific remedies for each identified issue. p. 138
What are the valve clearance specifications?
The valve clearance specification for both inlet and exhaust valves, when cold, is 0.25 mm (0.0098 in.) for both 4DQ7 and S4S models. This specification is crucial for proper engine operation and should be checked and adjusted as needed. p. 3
What torque specifications are listed?
The manual lists various torque specifications for different components. For example, the cylinder head for the 4DQ7 model requires a tightening torque of 12.0 ± 0.5 kgf·m (87 ± 4 lbf·ft) or 118 ± 5 N·m. Specific tables are provided for 4DQ7 and S4S engines, as well as for standard bolts, studs, and plugs. p. 22
What are the common electrical problems?
Common electrical problems include a defective starter switch, a faulty starting motor magnetic switch, or a free wheel. Other issues can be a battery voltage drop, open or short circuits in the glow plugs or pilot lamp, and defective alternator or alternator relay. Improper wiring can also lead to electrical malfunctions. p. 140
Is this Mitsubishi 4DQ7, S4S Service Manual a digital download?
A 147-page Service Manual in scanned PDF format, available the moment you complete checkout. View on computer, tablet, or phone, with no shipping wait.
Can I print specific sections of this Mitsubishi 4DQ7, S4S Service Manual?
Yes. The PDF has no DRM restrictions, so print any page or section you need for your shop. Works with any standard printer.
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