Engine management system - MEMS (Injectors): Description and operation

Injectors

The four fuel injectors are fitted between the pressurised fuel rail and the inlet manifold. Each injector comprises a solenoid operated needle valve and a specially designed nozzle to ensure good fuel atomisation.

The injectors are controlled in grouped mode with 2 & 3 being grouped and 1 & 4 being grouped, with the injectors in each group being operated alternately.

The ECM determines when to operate the injectors based on the signal it receives from the CKP sensor. The ECM provides an earth signal for the period the injectors are required to be open, the injector solenoids are energised and fuel is sprayed into the inlet manifold onto the back of the inlet valves. The ECM carefully meters the amount of fuel injected by adjusting the injector opening period (pulse width). During cranking, when the engine speed is below approximately 400 rev/min, the ECM increases the injector pulse width to aid starting. The amount of increase depends upon engine coolant temperature. To prevent flooding during cranking, the ECM periodically inhibits the operation of the injectors.

Throttle Housing and Inlet Manifold

The plastic throttle housing is located between the plastic inlet manifold and air intake hose and is sealed to the manifold by an ’O’ ring. The throttle housing incorporates a throttle disk which is connected to the throttle pedal via the throttle lever and a cable. Mounted on the throttle housing is the throttle position sensor. The throttle housing also provides the attachment point for the throttle cable mounting bracket. The throttle cable is connected to the throttle disk via a semi circular lever. An Idle Air Control (IAC) valve is mounted on the inlet manifold.

1. Throttle housing
2. Throttle valve
3. TP sensor
4. IAC valve hose
5. Engine ventilation hose
6. Inlet manifold
7. IAC valve

The throttle disk position is set during manufacture and is not adjustable. A throttle position screw is fitted to allow the throttle disk to close at its optimum position.

There are two breather hoses from the camshaft cover; one hose is fitted to the inlet manifold and the other is fitted to the throttle housing. Both pipes are connected to a gauze filter in the camshaft cover to prevent engine oil being drawn into the engine by the substantially greater manifold depression.

The throttle position (TP) sensor is attached to the throttle disk pivot shaft and secured to the throttle housing with two Torx head screws.

The IAC valve is attached to the inlet manifold with four Torx head screws. The valve is connected to the inlet manifold via a port and sealed with an O-ring. A rubber hose connects the valve to the inlet side of the throttle housing.