Mitsubishi 4DQ3 User Manual

SERVICE MANUAL
三菱ディーゼルエンジン
三菱ディーゼルエンジン
MITSUBISHI
DIESEL ENGINE
4DQ3, 4DQ30
MITSUBISHI HEAVY INDUSTRIES, LTD.
No. 5-1, Marunouchi, 2-chome Chiyoda-ku, Tokyo Japan
Phone: Tokyo (03) 212-3111 Telex: J22282, J22443 HISHIJU
SERVICE MANUAL
99609-50000
DEC 1985

Mitsubishi 4DQ3 Specifications

General

Engine Model	4DQ3
Cylinders	4
Engine Type	Diesel
Cooling System	Water-cooled
Aspiration	Naturally Aspirated

Summary

Major Data and Specifications

Inspection and Repair

Check gasketed surface of cylinder head for flatness.

Precombustion Chamber Jet Replacement

Procedure for removing and replacing precombustion chamber jets.

Valve Guides and Valve Seats

Check Each Valve

Inspect valves for carboning, burning, wear, or defects.

Check Each Valve Guide for Wear

Measure valve guide inside and stem outside diameters.

Valve Face and Valve Seat

Check valve face and seat for wear; reface if needed.

Valve Springs

Inspect Each Spring

Check valve springs for cracks, squareness, free length, and installed length.

Cylinders

Using a Cylinder Gauge

Measure cylinder sleeve ID in two directions at three places.

Pistons and Piston Rings

Pistons

Inspect pistons for wear, cracks, melting, or fusion.

Measure the Outside Diameter of Piston

Measure piston OD perpendicular to each other. Replace if exceeding limit.

Replacing Pistons

Replace pistons if measurement exceeds service limit. Match weight variance.

Piston Ring Gaps

Check piston ring gap using a thickness gauge.

Piston Ring Grooves

Measure side clearance of compression and oil rings.

Piston Pin Bosses

Check pin clearance in piston pin boss and on connecting rod.

Connecting Rod Alignment and Bearings

Check the Connecting Rod

Inspect connecting rod for cracks, especially in fillets.

Mount Each Connecting Rod

Check connecting rod for bend and twist using an aligner.

Rod Bend and Twist Check (No Aligner)

Check rod for bend and twist using measurements and a press.

Check Rod Straightness with Piston

Check rod straightness by measuring on a surface plate.

Check Connecting Rod End Play

Measure connecting rod end play with a thickness gauge.

Check Main Bearings

Inspect main bearings for wear, damage, or seating. Check radial clearance.

Crankcase

Inspect Crankcase Surfaces

Check crankcase for cracking, bore wear, and flatness of mating faces.

Crankshaft

Journals

Inspect journals for surface flaws and measure for wear, out-of-round, and taper.

Crankpins

Inspect crankpins for surface flaws and measure for wear, out-of-round, and taper.

Grinding the Crankshaft

Refinish journals and crankpins to undersize bearing dimensions.

End Play

Check crankshaft end play at the thrust bearing.

Runout

Measure crankshaft deflection using a dial gauge.

Main Bearings

Inspect main bearings for wear, damage, or seating. Check radial clearance.

Camshaft

Check Camshaft End Play

Check camshaft end play; replace thrust plate if limit is exceeded.

Inspect Camshaft Journals

Inspect camshaft journals for wear and damage.

Measure Each Cam of the Camshaft

Measure cam height and diameter to check wear.

Check Camshaft for Runout

Check camshaft for runout; straighten or replace.

Tappets and Tappet Holes

Inspect Riding Face of Each Tappet

Inspect tappets for wear, contact pattern, and cracks.

Check Tappet Fit in Hole

Check tappet fit in bore; replace tappet or crankcase if worn.

Timing Gears

Check Gear Mesh Backlash

Check gear backlash; replace worn gear if limit exceeded.

Check Idler Bushing Radial Clearance

Check radial clearance between idler bushing and shaft.

Check Idler End Play

Check idler end play with a thickness gauge.

Inspect Timing Gears

Inspect camshaft, crankshaft, idler, and injection pump gears.

Reassembly

Reassemble Connecting Rod and Piston

Assemble connecting rod to piston and install piston rings.

Reassemble the Crankcase

Drive camshaft bushings and idler shaft into crankcase.

Install the Piston Assembly

Install connecting rod bearing, piston rings, and piston assembly into crankcase.

Install the Crankshaft

Install thrust plate, woodruff keys, and crankshaft gear.

Install the Main Bearing Caps

Install main bearing caps, align with dowel pins, and tighten bolts.

Install the Connecting Rod Bearing Caps

Install connecting rod bearing caps, aligning marks.

Install Retainers and Gaskets

Install retainers, oil pan gasket, and rubber packing.

Install the Front Plate

Apply sealant to packing, attach front plate, install and tighten bolts.

Install the Idler Gear

Install idler gear by matching timing marks.

Install the Oil Pump Assembly

Install oil pump assembly and mesh drive gears.

Install Rear Plate and Flywheel

Drive dowel pin, secure flywheel with bolts and lock washers.

Reassemble Cylinder Head

Drive valve guides into cylinder head.

Install Cylinder Head Assembly

Place gasket, install cylinder head using guide bolts, tighten bolts.

Install Push Rods and Rocker Shafts

Install push rods, rocker shafts, oil pipes, and brackets.

Adjust Valve Clearance

Adjust valve clearance for intake and exhaust valves at specified TDC positions.

Install Rocker Case

Install the rocker case.

Install Water Pump Assembly

Install water pump assembly, bypass hose, and oil pipe.

Install Timing Gear Case

Install timing gear case with copper packing for bolts.

Install Water Pump Pulley and Crankshaft

Drive pump pulley and crankshaft pulley; install washer and tighten nut.

Install Fan Belt

Attach fan belt and adjust tension.

Lubricating System

Lube Oil Circulation

Explains the path of oil from the pan through the filter to engine parts.

Oil Pump

Details the location and function of the oil pump.

Oil Pump Disassembly

Step-by-step procedure for disassembling the oil pump.

Oil Pump Inspection

Inspection procedures for oil pump rotors, shaft, and body clearances.

Oil Pump Reassembly

Steps for reassembling the oil pump.

Oil Filter

Describes the oil filter mounting, bypass valve, and relief valve.

Oil Filter Disassembly

Procedure to remove the oil filter and relief valve.

Oil Filter Inspection

Inspect the filtering element and filter bracket.

Cooling System

Coolant Circuit

Explains the flow of coolant through the engine and radiator.

Thermostat

Details the thermostat's function and operating temperatures.

Thermostat Disassembly

Procedure for removing the thermostat cover and thermostat.

Thermostat Inspection

How to test the thermostat's thermostatic action.

Water Pump

Describes the centrifugal water pump and its lubrication.

Water Pump Disassembly

Steps for disassembling the water pump.

Water Pump Inspection

Inspecting water pump operation, impeller, seals, and shaft journals.

Water Pump Reassembly

Steps for reassembling the water pump.

Bench Test

Visual Inspection

Inspect engine condition before and after starting on a dynamometer.

Performance Tests

Procedures for testing engine output, speed, and fuel injection.

Maintenance Standards

General

Engine specifications: RPM, compression pressure, oil pressure, valve timing.

Crankcase and Main Moving Parts

Standards for crankcase, cylinder sleeves, and related parts.

Main Bearings

Specifications for main bearing and thrust clearances.

Camshaft Bushing

Standards for camshaft journal fit and bushing installation.

Tappet Holes

Specifications for tappet fit into tappet holes.

Cylinder Head

Maintenance standards for cylinder head, valves, and springs.

Rockers

Specifications for rocker shaft diameter and fit.

Push Rods

Specifications for push rod runout.

Crankshaft

Standards for crankshaft journals, crankpins, fillet radius, and variances.

Pistons

Specifications for piston diameter, protrusion, and weight differences.

Piston Rings

Specifications for piston ring gap and groove fit.

Piston Pins

Specifications for piston pin diameter and clearance.

Connecting Rods

Standards for connecting rod bend, twist, and crankpin fit.

Connecting Rods (Continued)

Standards for connecting rod end play and weight differences.

Flywheel

Specifications for flywheel flatness and runout.

Camshaft

Standards for camshaft journal diameter, runout, and cam height.

Idler

Standards for idler end play, shaft diameter, and bushing fit.

Timing Gear Train

Standards for thrust journal width, shaft fit, and gear backlash.

Lubrication System

Standards for oil pump clearances and relief valve pressure.

Sealant Application Data

Tightening Torque

General Bolts and Nuts

Special Service Tools

Installing Valve Guides

Tooling and procedure for installing valve guides.

Removing Valve Guides

Tooling and procedure for removing valve guides.

Installing Intake Valve Inserts

Tooling and procedure for installing intake valve inserts.

Installing Exhaust Valve Inserts

Tooling and procedure for installing exhaust valve inserts.

Connecting Pressure Gauge for Compression Measurement

Tool and procedure for connecting a pressure gauge for compression testing.

Removing Idler Shaft

Tool and procedure for removing the idler shaft.

Rotating Crank Pulley for Engine Cranking

Tool for rotating the crankshaft pulley.

Installing Camshaft Thrust Plate

Tool for installing the camshaft thrust plate.

Removing/Installing Piston Rings

Tool for removing and installing piston rings.

Removing/Installing Idler Bushing

Tool for removing and installing idler bushings.

Removing/Installing Camshaft Bushings

Tools for removing and installing camshaft bushings.

Troubleshooting

Fuel System

Troubleshooting causes and remedies for fuel system issues.

Lubrication System

Troubleshooting causes and remedies for lubrication system issues.

Air System

Troubleshooting causes and remedies for air intake system issues.

Cooling System

Troubleshooting causes and remedies for cooling system issues.

Electrical System

Troubleshooting causes and remedies for electrical system issues.

Main Moving Parts

Troubleshooting causes and remedies for engine moving parts issues.