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

Injectors

The fuel injectors are fitted between the pressurised fuel rail and 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 group mode during cranking then sequentially when the engine is running on KV6 engines but grouped mode only on ’T’ series engines. The ECM determines when to operate the injectors based on the signal it receives from the crankshaft sensor on ’T’ series engines, or crankshaft and camshaft sensors on KV6 engines.

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 300 rev/min, the ECM increases injector pulse width to aid starting. The amount of increase depends upon engine coolant temperature. To prevent flooding, the ECM periodically inhibits the operation of the injectors.

Throttle housing - KV6

The twin bore throttle housing is attached to the inlet chamber and incorporates a throttle disc in each bore which are connected to the throttle pedal via the throttle lever and throttle cable.

A breather pipe is located ahead of each throttle disc. When the engine is running with the throttle disc open, both pipes are subjected to the venturi effect of the air flow to draw crankcase fumes into the manifolds.

When the throttle disc is closed and at small throttle openings, the crankcase fumes enter the plenum chamber via the part load circuit which have small diameter drillings in the cam covers. The small diameter drillings act as a restrictor to prevent engine oil being drawn into the engine by the substantially greater manifold depression.

Also incorporated in the throttle housing is the throttle position sensor.

Throttle housing - T series

The throttle housing is attached to the inlet manifold via a rubber sandwich plate. The throttle housing incorporates a throttle disc which is connected to the throttle pedal via the throttle lever and a cable.

There are two breather pipes connected to the throttle housing, one either side of the throttle disc. When the engine is running with the throttle disc open, both pipes are subject to manifold depression and draw crankcase fumes into the manifold. When the disc is closed, only the pipe on the inlet manifold side of the disc is subject to manifold depression. This pipe incorporates a restrictor to prevent engine oil being drawn into the engine by the substantially greater manifold depression.

Mounted on the the throttle housing are the throttle position sensor and stepper motor.