Diesel Fuel Supply System — Basic Design

Unlike petrol engines, diesel injection systems operate under high pressure. As a result, injection pumps, including process-regulating peripheral units, are very different from their counterparts in gasoline engines. In diesel engines, engineers distinguish between in-line injection pump, single-plunger distribution injection pump, main (Common-Rail) and a pump/nozzle injection system. Under the hood of the Focus Diesel is a single-plunger distribution injection pump (Bosch VP-30) delivers fuel through injection pipes and nozzles directly to the combustion chambers. The injection pump is driven by a chain from the crankshaft. On the top side of the pump is an electronic pump control unit (PCU). It uses information from the steering angle sensor as well as the transmission control unit (RSM) and takes signals from there to control the high-pressure solenoid valve and adjust the start of fuel supply.

Fuel is delivered to the injectors with five holes through injection pipes of the same length. The injectors are fixed to the cylinder head with clamping screws.

Copper sealing washers protect their top from direct contact with the cylinder head. Always replace the sealing washers after each dismantling of the injectors. The Focus has relatively thin nozzles (pin nozzles). Injection direction of five injector holes «aimed» almost to the center of the recess of the specially profiled piston inside the cylinders.