Fuel delivery system - Td5 (Injectors): Description and operation (page 2 of 2)

The five injectors are located in the cylinder head, adjacent to the camshaft, with the nozzle of each injector protruding directly into the cylinder. Each injector is sealed into the cylinder head with an 'O' ring and a copper washer and secured with a clamp and bolt.

Each injector is operated mechanically by an overhead camshaft and rocker and electrically by a solenoid controlled by the ECM. Each injector is supplied with pressurised fuel from the pump via the regulator housing and internal drillings in the cylinder head. ENGINE MANAGEMENT SYSTEM - Td5, DESCRIPTION AND OPERATION, Description.

The solenoid housing is secured to the injector body with two cap screws and is a sealed unit with a two pin electrical connector on its top face.

The injector body is machined from a forging. The body has a machined central bore which locates the push rod. A thread on the outer diameter provides the attachment for the nozzle cap nut. The body also provides attachment for the solenoid housing.

The injector push rod is operated from the rocker and cam assembly by a socket. The push rod is located in the housing bore and retained in its extended position by a push rod return spring. The powerful spring ensures that the push rod socket is always in contact with the rocking lever and the cam.

The lower part of the injector housing locates the spring loaded nozzle. The nozzle is retained in the housing by a nozzle cap nut which is screwed onto the housing. The nozzle cap nut has four holes around its circumference which connect to the fuel return drilling in the cylinder head. The injector housing has ports located above the nozzle cap nut which connect with the fuel delivery drilling in the cylinder head. An 'O' ring seals the injector in the machined location in the cylinder head and a copper washer seals the injector from the combustion chamber.

The injectors are supplied with pressurised fuel from the fuel pump, via the pressure regulator housing and internal drillings in the cylinder head. Each injector sprays fuel directly into the cylinder at approximately, 1500 bar (22000 2 2

lbf.in ) on pre EU3 models and 1750 bar (25500 lbf.in ) on EU3 models, atomising the fuel and mixing it with intake air prior to combustion.

The camshaft and rocker arrangement depresses the push rod which pressurises the fuel within the injector. When the injector is required to inject fuel into the cylinder, the ECM energises the solenoid which closes a valve within the solenoid housing. The closure of the valve stops the fuel entering the return line to the pump, trapping it in the injector. The compression of the fuel by the push rod causes rapid pressurisation of the fuel which lifts the injector nozzle, forcing the fuel into the cylinder at high pressure. The ECM controls the injection timing by altering the time at which the solenoid is energised and the injection period by controlling the period for which the solenoid is energised. ENGINE MANAGEMENT SYSTEM - Td5, DESCRIPTION AND OPERATION, Description.