157Service Manual – CS7000Engine System - LPGThis chapter covers the things “on top” of the mechanical engine that make it run, such as the fuel system,governor control and ignition system. It also includes routine engine maintenance information andtroubleshooting of engine starting or running problems. See the Kubota WG972 E3 Workshop Manual9Y111-05710 for detailed information related to the complete mechanical engine.Functional DescriptionOne of the engines available in the CS7000 is a LPG Kubota (WG972-GL-E3-NFK-1). It is a threecylinder, liquid cooled, naturally aspirated engine. The fuel system does not utilize a control module. It ismechanically controlled. The ignition system is “self-contained”. That is, it has no interaction with the fuelsystem and shares no components with it.The fuel system begins with a 33 pound propane fuel tank which is horizontally mounted on the right side ofthe engine compartment. The tank swings out to provide easier access to the engine compartment. There isan in-line pressure relief valve and a pressure switch between the tank and the fuel pressure vaporizer/regulator. The fuel pressure vaporizer/regulator takes in high-pressure propane liquid, changes it to a vaporand reduces it to a constant low pressure gas for the engine to draw in and burn. The change from liquid togas absorbs a lot of heat and acts as an air conditioner. To prevent frosting up the regulator, it is heatedwith engine coolant. The vaporizer/regulator supplies gaseous fuel to the carburetor through a hose. Thecarburetor has an additional fuel shut off solenoid that must be energized for fuel to flow through thecarburetor to the engine.The engine RPM is controlled with a Woodward L-Series governor/speedactuator based on requests from the main machine controller. The mainmachine controller sends signals to the Woodward L-Series governor/speedactuator to request one of three engine speeds based on operator request orcleaning mode. The actuator has a “built in” microprocessor which receives therequests and in turn physically moves the carburetor/mixer throttle blade toachieve the requested engine speed.The cooling system consists of a standard radiator and belt driven fan. Notethat the fan pushes air away from the engine and out through the radiator.Propane Fuel Tank Fuel Vaporizer/RegulatorKubota LPG EngineCarburetorFuelshut offsolenoidWoodward L Series Actuator
