CARRIER-PLANETARY 9W7839 - Caterpillar

Illustration 1 g01915500
(1) Fuel filter base
(2) Temperature sensor
(3) Fuel pressure sensor (secondary filter inlet)
(4) Fuel pressure sensor (secondary filter outlet)
(5) Cylinder head
(6) Fuel injector
(7) Low-pressure regulator
(8) Fuel tank
(9) Electric priming pump
(10) Primary fuel filter
(11) Fuel transfer pump
(12) Electronic control module (if equipped) The fuel supply circuit is a conventional design for electronic unit injector diesel engines. Fuel transfer pump (11) of the circuit is a gear-type pump with positive displacement. The fuel transfer pump is located in the front of the engine at the lower left corner. The fuel transfer pump is mounted to the front timing gear cover. The fuel transfer pump is driven by the front gear train.The fuel transfer pump draws fuel from fuel tank (8). The fuel passes through primary filter/water separator (9). The fuel passes into the fuel transfer pump and the fuel is then pressurized. The fuel transfer pump incorporates a check valve in order to permit a fuel flow around the gears for hand priming. The fuel transfer pump also incorporates a relief valve in order to protect the system from extreme pressure. The excess fuel flow that is provided by the fuel transfer pump is used in order to cool the electronic unit injectors. The excess fuel flow also purges the air from the fuel system.The fuel from the fuel transfer pump flows through the fuel filter at fuel filter base (1). Fuel temperature sensor (2) is mounted in the fuel filter base. The Engine Control Module (ECM) (12) uses the sensor to monitor the temperature of the fuel that is entering the engine. The information is used by the ECM to calculate a fuel correction factor during engine operation. Fuel priming pump (8) is positioned on the fuel filter base in order to prime the system when air has been introduced into the fuel system. For more information on priming the fuel system, refer to Testing and Adjusting, "Fuel System - Prime".The fuel leaves the fuel filter base and flows through the fuel supply line to the cylinder head. The fuel enters the cylinder head at the front of the engine. Fuel is delivered to the electronic unit injectors through fuel manifold that is drilled into the cylinder head during the manufacturing process.Excess fuel exits the cylinder head at the rear. The fuel returns to the fuel filter base through the fuel return line to the pressure regulating valve that is incorporated into the fuel filter base. The pressure regulating valve maintains a sufficient amount of back pressure in the system in order to fill the electronic unit injectors. After the fuel passes through the pressure regulating valve, the fuel returns to the fuel tank. The fuel flows continuously from the fuel supply through the electronic unit injectors in the head and back to the tank.Fuel System Electronic Control Circuit
The injection pump, the fuel lines, and the nozzles that are used in the traditional Caterpillar diesel engines have been replaced with a mechanically actuated electronically controlled unit injector in each