Mitsubishi 4G63, 4G64 Gasoline Engine Factory Service & Repair Manual (P/N 99729-74120, 99729-75100)

This PDF package combines the Mitsubishi 4G63/4G64 gasoline-engine service manual with the matching Liquefied Petroleum Gas Supplement. The set contains two files, 113 and 77 pages respectively, for 190 PDF pages total. The engine manual is identified on its cover as 99729-74120; the LP-gas supplement is 99729-75100.

Engine and Serial Coverage

The engine manual covers Mitsubishi 4G63 and 4G64 four-cylinder OHC engines used in gasoline and LP-gas configurations. Its engine-identification table lists 4G63/4G64 engine numbers AA0001 through YY9999 and separates the actual build codes: 4G63-32-FDA, -FDS and -FDB gasoline versions; 4G63-32-FLA, -FL and -FLB LP-gas versions; and 4G64-32-FDS/-FDB gasoline plus -FL/-FLB LP-gas versions.

The LP-gas supplement extends fuel-system coverage to 4G63 AA0001-ZZ9999, 4G64 AA0001-ZZ9999 and 6G72 0A0001-0Z9999. Its later CARB Tier 1 section is specifically for the S-15G emissions-control system used on 2001-2002 model-year applications and describes the 4G63 2.0 L and 4G64 2.4 L closed-loop LPG system.

A useful scope distinction: the engine manual describes service with the engine removed from the truck. Chassis-level engine removal, on-truck inspection and model-specific vehicle service are referred to separate truck service manuals.

Engine Repair Depth and Specifications

This is engine repair material, not an operator or routine-maintenance booklet. Coverage runs through timing belt service, ignition and distributor work, carburetor and air-governor repair, lubrication and cooling systems, intake/exhaust manifolds and water pump, rocker arms and camshaft, cylinder head and valves, front case and oil pump, pistons and connecting rods, crankshaft and cylinder block, alternator and starter overhaul, plus symptom-based troubleshooting.

The specification sections give 1,997 cc for the 4G63 and 2,350 cc for the 4G64, 1,128 kPa (163.5 psi) compression pressure, 4.8 L (1.27 U.S. gal) engine-oil capacity including the filter, and 3.1 L (0.82 U.S. gal) coolant capacity in the engine proper. Gasoline ignition timing is listed at 4° BTDC/740 rpm and LP-gas timing at 9° BTDC/740 rpm. Torque tables include conventional dry torque and torque-plus-angle fasteners; examples include the 118 N·m crankshaft bolt, 88 N·m camshaft sprocket bolt and 132 N·m flywheel bolts. Timing-belt adjustment/inspection is called for at the first PM or 200 hours, inspection for wear and cracking at 2,000 hours or one year, and replacement at 3,000 hours or 18 months.

A serial-related rebuild detail appears in the crankshaft/cylinder-block section: from serial 4C1709 and up, the manual identifies a changed cylinder block together with a new-style crankshaft, new No. 3 main-bearing choices and a new thrust-bearing set. That build break matters when selecting internal engine parts during repair.

Factory procedures include timing-belt removal and tensioning, cylinder-head and valve service, valve-stem seal replacement, lash-adjuster testing and air bleeding, oil-pan/front-case removal, piston-pin service, crankshaft and bearing inspection/selection, cylinder boring, carburetor overhaul, and alternator/starter/distributor disassembly and testing. Named special tools include MD998727 Oil Pan Remover, MD998440 Lash Adjuster Leak-Down Tester, MD998772 Valve Spring Compressor, MD998778 Crankshaft Sprocket Puller and MD998780 Piston Pin Setting Tool.

LP-Gas, CARB Tier 1 and Diagnostics

The LP-gas supplement covers the tank, pressure-relief valve, fixed liquid-level gauge, service valve, vacuum fuel-lock filter, hydrostatic relief valve, converter/vaporizer and LP-gas carburetor or mixer. It includes disassembly/reassembly and inspection/adjustment for the mixer, converter/regulator and VFF30 fuel lock, plus idle, power-mixture and gas-leak checks.

For S-15G CARB Tier 1 systems, the manual goes deeper into electronic diagnosis: ECU versions 1 and 2, oxygen sensor, pedal sensor, engine-block temperature sensor, fuel-control solenoid valve, electronic throttle body, three-way catalytic converter and check-engine light logic. Warm idle is 700 rpm, governed speed is 2700 rpm, and overspeed protection shuts the fuel lock off if engine speed exceeds 3100 rpm for more than two seconds. Over-temperature logic is also documented, including the 105°C warning threshold, 115°C limp-home condition and 1200-rpm reduced-speed mode.

The diagnostic section specifies the laptop diagnostic kit 93060-06300 and handheld diagnostic unit 93060-06400. Live-data coverage includes pedal angle, MAP, engine temperature, oxygen-sensor voltage, battery voltage, FCSV dwell and operating mode. The S-15G screen gives 36-38 kPa MAP at no-load idle, a 0.10-0.85 V oxygen-sensor range and approximately 14.5 V while charging. Blink-code tables identify fuel-system, pedal-sensor, engine-temperature, battery-voltage and TACH/RPM faults. Diagrams include the 4G63 Side Cutaway View, LP-gas Device Layout, Mixer and Throttle Body Internal Gas Flow, CARB Tier 1 Vacuum System Diagram, S-15G Fuel System Wiring Schematic, and ECU Pin Location and Function.

There are several manual-specific repair traps worth knowing before disassembly. Excess FIPG can squeeze into and restrict an engine fluid-feed passage. On the VFF30 fuel lock, bolts that are too long can severely damage the lockoff, while carburetor cleaner can attack its synthetic-rubber seals. The throttle-sensor section also warns that excessive accelerator force with the floor plate removed can damage the potentiometer.

LP-gas tank, valve and level-indicator work involves high-pressure components; the supplement directs that disassembly to legally qualified personnel and certified shops.