Operation of the gasoline engine management system (VW Polo 4)

The electric fuel pump takes fuel from the fuel tank and delivers it through a filter located under the tank to the fuel manifold. The pressure regulator, depending on the engine, maintains the fuel pressure in the system constant and equal to 3 bar.

Electrically controlled valve injectors inject fuel into the engine intake manifold in pulses, directly in front of the intake valves. The engine control unit controls the operation of the valve injectors sequentially, i.e. in accordance with the firing order of the cylinders. The unit regulates the injection duration and, thus, the amount of fuel injected.

The air sucked in by the engine passes through the air filter and through the throttle valve assembly via the intake manifold to the intake valves. The amount of air entering the engine is regulated by the throttle valve, the position of which is changed by a stepper motor based on commands from the engine control unit.

The engine control unit is located in the engine compartment, on the left at the rear near the front wall. This is a small, high-performance computer. The control unit calculates the optimal ignition timing, the injection start time, and the amount of fuel injected.

Signals from various sensors and instructions to actuators ensure optimum engine operation in every driving situation. If important sensors fail, the control unit switches to a backup program to avoid engine damage and to continue driving. In this case, the engine runs unevenly and tends to stall when the accelerator pedal is pressed.