Cummins ISX11.9 CM2250 – Service Manual 006-999   Injectors and Fuel Lines – Overview

WARNING  Fuel is flammable. Keep all cigarettes, flames, pilot lights, arcing equipment, and switches out of the work area and areas sharing ventilation to reduce the possibility of severe personal injury or death when working on the fuel system.

High-pressure common rail fuel systems use solenoid-actuated injectors. High-pressure fuel flows into the side of the injector. When the solenoid is activated, an internal needle lifts and fuel is injected. The clearances in the nozzle bore are extremely small and any dirt or contaminants can cause the injector to stick. This is why it is important to clean around all of the fuel connections before servicing the fuel system. Also, cap or cover any open fuel connections before a fuel system repair is performed.

To prevent damage from debris and contamination, cover, cap, or plug any openings as soon as possible when servicing the fuel system. Caps and plugs can be found in the Clean Care Kit, Part Number 4919073.

CAUTION  To reduce the possibility of engine damage, always use the proper torque value and the proper torquing sequence on the high-pressure line nuts, injectors, and fuel connectors.

High-pressure fuel is supplied to the injector from the fuel rail by an injector supply line and a fuel connector. The fuel connector pushes against the injector body when the fuel connector nut is tightened. The injector supply line is then connected to the fuel connector.The torque and sequence for this joint are critical. If the nut or line is undertightened, the surfaces may not seal and a high-pressure fuel leak can result. If the nut is overtightened, the connector and injector will deform and can cause a high-pressure fuel leak. This leak will be inside the head and will not be visible. The result will be a fault code, low power, or no start condition.

If the injector is not fully seated prior to the installation of the high-pressure connector, the joint will not seal.

To prevent damage from debris and contamination, cover, cap, or plug any openings as soon as possible when servicing the fuel system.  Caps and plugs can be found in the Clean Care Kit, Part Number 4919073.

All injectors drain into a common fuel return drilling contained within the cylinder head. Any excess fuel is returned to a drain line, attached to the rear of the cylinder head, to the fuel drain manifold, then to the fuel tank. A back-pressure valve is located on the back of the cylinder head where the drain line is attached.

The electronic control module (ECM) controls the fueling of the engine by actuating the injector solenoids. An electronic pulse is sent to the solenoids to lift the needle and start the injection event. By electronically controlling the injectors, there is a more precise and accurate control of fueling quantity and timing. Also, multiple injection events can be achieved by electronically controlling the injectors.

The engines covered in this manual require the original equipment manufacturers (OEMs) to mount a 10-micron, suction-side filter, prior to the OEM fuel supply connection, located at the fuel filter head. The 10-micron filter performs water stripping and includes a water-in-fuel sensor. The water-in-fuel sensor must be installed. If not, a fault code warning lamp will be active.

The engines covered in this manual also include a 5-micron pressure-side fuel filter. The pressure-side filter will be located downstream of the gear pump, before the high-pressure fuel pump inlet. If a water-in-fuel fault is experienced, drain the water stripping suction-side filter and change the pressure-side fuel filter.