Fuel Injectors, Basic Function - GF07.03-P-2000A

Engine All with direct injection 

Courtesy of MERCEDES-BENZ USA

Sample diagram with fuel injectors 

Overview 

This document contains information on:

• General 
• Function 

General 

Fuel injectors (1.1 to 1.4) inject fuel, which is under high pressure, directly into respective cylinder.

The respectively injected fuel quantity depends on the actuation duration of the corresponding fuel injector (1.1 to 1.4).

The injection quantity is determined by additional factors:

• Opening and closing speed of nozzle needle
• Needle lift height
• Nozzle geometry
• Fuel distributor pressure

Fuel injectors (1.1 to 1.4) switch extremely fast and are capable of injecting the smallest fuel quantities.

Short response times of fuel injectors (1.1 to 1.4) allow multiple injection with short breaks during combustion cycle.

Function 

This is shortened by the discharging of the piezo actuator in the fuel injector (1.1 to 1.4). With a coupler module (travel-stroke amplifier), the movement is transferred to the nozzle needle of the nozzle module. The nozzle needle lifts of the nozzle module and exposes the injection holes of the nozzle module. The injection occurs until the piezoceramics are recharged by the combustion engine control unit. The piezo actuator expands due to the charging. The nozzle needle closes the injection holes of the nozzle module. In the case of "circuit 61 OFF" and no actuation of circuit 30 g of the combustion engine control unit, the nozzle needle is pressed by a spring into the seat so that the injection holes of the nozzle module remain closed.