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

• Covers 2001–2002 Mitsubishi forklift trucks equipped with 4G63, 4G64, and 6G72 engines utilizing the S-15G LP-gas system
• Details the configuration of the S-15G emissions control system, originally introduced to meet early CARB Tier 1 requirements
• Official Mitsubishi publication P/N 99729-75100
• Contains 47 pages of system diagrams, diagnostic screen layouts, and troubleshooting trees

System Coverage and Diagnostic Procedures

This documentation breaks down the S-15G fuel management architecture. It specifically outlines the integration between the ECU, fuel control solenoid valve (FCSV), and the vaporizing converter. You will find dedicated sections covering the mechanical structure of the LP-gas tank. This includes pressure relief mechanisms and liquid level indicators, as well as the operational principles driving the carburetor and mixer assemblies. Since working with highly pressurized LP-gas fuel systems presents inherent flammability risks, always verify system depressurization and maintain proper shop ventilation before inspecting these components.

The manual maps out the S-15G diagnostic screen layout. Technicians can use this reference to monitor manifold absolute pressure, pedal angle units, and oxygen sensor voltage in real time. It also defines the strict criteria for open-loop versus closed-loop operation. You need to know exactly what conditions prompt the ECU to lock the air-fuel ratio onto stoichiometric targets.

Specification Highlights and Operating Parameters

Hard diagnostic parameters and system thresholds help identify operational deviations fast. For example, correct operation dictates a primary chamber pressure within the converter of 9.8 to 14.7 kPa (0.1–0.15 kgf/cm²) [1.4–2.1 psi]. Engine manifold pressure for the 4G63 and 4G64 engines sits between 35 and 45 kPa at idle. This rises to 42–47 kPa at high idle. The target value for the throttle sensor potentiometer is a pedal angle of 35 +/- 5 units.

The supplement also decodes system fault indicators. It explains blink codes for fuel system errors and battery voltage anomalies, pulling directly from the ECU diagnostic output.