Mitsubishi 4G63/4G64/6G72 Forklift Factory Service Manual | LP Gas System (P/N 99729-75100, 99789-74120)

• 683-page set of three Mitsubishi factory service publications: Chassis/Mast Service Manual 99739-74100 (402 pages), GM 4.3L G6 Gasoline Engine Service Manual 99789-74120 (204 pages), and Liquefied Petroleum Gas Supplement 99729-75100 (77 pages).
• Chassis and mast coverage spans FG35 F29-00011-up and FG40 F29-50001-up with the Mitsubishi 6G72 gasoline engine; FD35 F19B-00011-up, FD40 F19B-50001-up, FD45 F28A-00011-up, and FD50C/FD50 F28A-50001-up with the Mitsubishi S6S diesel engine, including manual- and powershift-specific sections where fitted.
• Major chassis repair procedures address power-train removal, dry- and wet-clutch service, manual transmission overhaul, 1-speed and automatic 2-speed powershift diagnosis, torque-converter and control-valve work, axle and reduction-differential repair, brake and steering service, hydraulic testing, and dual-stage panoramic-mast disassembly and adjustment.
• The GM 4.3L G6 engine book applies to engine serial 003103-up and the listed FGC35K–FGC70K, FG35–FG50, and FG40K–FG50K chassis families. It covers engine replacement, base-engine teardown and rebuilding, measuring and machining checks, ignition and ECU diagnosis, and gasoline/LP fuel-system repair for units built before 01/01/2004.
• LP-gas coverage includes 4G63 AA0001–ZZ9999, 4G64 AA0001–ZZ9999, and 6G72 0A0001–0Z9999 tank, VFF30 fuel-lock, Model J converter/regulator, and CA100 mixer service, plus the dedicated 2001–2002 S-15G CARB Tier 1 closed-loop section for 4G63 and 4G64 engines.
• Diagnostic and reference material provides chassis electrical and hydraulic schematics, powershift hydraulic circuits, GM ECU input/output tables and flash-code diagnosis, S-15G live-data screen layouts and troubleshooting trees, LP vacuum and wiring schematics, ECU pin functions, special-tool lists, torque tables, pressure-test data, wear limits, capacities, and adjustment specifications.

Configuration Coverage and Manual Boundaries

This PDF set combines three separate service publications, so the engine and fuel sections must be matched to the truck rather than treated as one universal configuration. The chassis/mast publication, 99739-74100, is the chassis/mast book for the 6G72-powered FG35/FG40 and S6S-powered FD models. It calls for separate 6G72 and S6S engine manuals; those internal-engine publications are not included here. The GM engine publication, 99789-74120, instead covers the 4.3L G6 used with the FGC and FG chassis families listed on its cover.

The LP-gas supplement, 99729-75100, is not a full engine overhaul book. Its general chapters cover 4G63, 4G64, and 6G72 fuel-system hardware, while the S-15G closed-loop CARB Tier 1 section is specifically identified with the 4G63 2.0L and 4G64 2.4L engines. The chassis book also separates manual, 1-speed powershift, and automatic 2-speed powershift procedures and gives serial-break guidance for different fan-belt access-hole arrangements.

System Coverage and Factory Repair Procedures

The chassis/mast publication uses exploded diagrams, disassembly sequences, inspection criteria, and reassembly notes for the covered driveline, axle, brake, steering, hydraulic, and mast assemblies. Transmission work includes oil-pressure measurement, clutch-valve testing, stall-speed and starting-acceleration tests, and inching-pedal adjustment. Mast sections address lift-bracket separation, chains and rollers, lift cylinders, shim locations, wear strips, and final adjustment. Dedicated troubleshooting tables run across the electrical system, clutches, transmissions, axles, brakes, steering, hydraulics, and masts.

The GM engine book moves from condition diagnosis into workshop-level rebuild work. It covers compression and misfire testing, valve-train and engine-noise diagnosis, lubrication faults, cylinder-head and valve service, timing chain and balance-shaft work, camshaft-bearing replacement, crankshaft and rear-seal service, block inspection and cylinder boring/honing, piston and connecting-rod repair, and bearing-clearance checks. Separate sections handle the carburetor, electrical throttle/governor system, distributor timing, alternator, starter, and the pre-2004 gasoline and LP fuel systems. The LP chapter includes on-truck converter pressure testing, lockoff and regulator service, CA100 mixer repair, exhaust-analyzer adjustment, governor setting, and accelerator-cable adjustment.

Diagnostic Screens, Schematics, and Special Tools

The S-15G section maps the ECU, fuel control solenoid valve, converter, mixer/throttle body, oxygen sensor, pedal sensor, engine-temperature input, three-way catalyst, and dash fault light. Version 1 and Version 2 ECU illustrations and separate pneumatic- and cushion-model exploded views help distinguish the installed hardware. The text defines open-loop and closed-loop control, throttle/governor behavior, limp-home reactions, diagnostic-kit installation, adjustment screens, D-code displays, blink codes, fault effects, and troubleshooting trees. The data stream covers manifold pressure, pedal angle, oxygen activity, battery voltage, engine and selected speed, operating mode, actuator output, LP lockout, and dash-light status. The ECU does not retain S-15G fault codes after a restart; the condition must remain present for the next self-test to report it.

Representative drawings include the 1-speed powershift Hydraulic System Schematic, control-valve sectional views, dual-stage panoramic-mast disassembly diagrams, the GM ECU Input/Output Interfaces and ECU Schematic, and the S-15G CARB 1 Tier 1 LP Fuel Vacuum System Diagram with its wiring schematic and ECU pin-function table. Referenced tools include the 64309-17701 pressure gauge kit, J 33049 camshaft-bearing service kit, J 36660 electronic torque-angle meter, 91868-02300 ECU diagnostic tester, and S-15G laptop and hand-held diagnostic units 93060-06300 and 93060-06400.

The manuals flag several easy-to-miss damage risks. Overlong VFF30 mounting bolts can severely damage the lockoff, carburetor cleaner attacks its synthetic rubber seals, and steel fittings in the converter coolant passages can deteriorate the casting through electrolysis. During GM engine repair, matched lifters, bearings, pistons, rods, and related parts must return to their original positions. An extended converter-stall run can destroy the torque converter, while restarting with the powered timing shunt connected can damage the ECU or EST module.

LP-gas work requires the tank supply to be shut off, the fuel circuit safely depressurized, and the shop kept well ventilated before fittings or components are opened. Hydraulic pressure must be relieved and the mast, forks, and other raised assemblies securely supported before inspection or repair.