Lucas MK1 and MK2 fuel / petrol injection



Maserati Manual MK1
Mistral + 3500 GT Owner's Manual

                                               Control is achieved by adjustment of the position of the control stops which determine the length of shuttle stroke
                                             and hence the quantity of fuel delivered. Fig. 6 shows a simplified schematic arrangement of the control mechanism.
                                             A cam follower has an abutment face against which the control stops in the metering distributor are forced by fuel
                                             pressure, while at the other end of the follower a small roller bears against a fuel cam of predetermined slope. The
                                             hydraulic loading of fuel pressure is offset by a balance spring surrounding the follower, resulting in only light pressure
                                             between the roller and fuel cam. Thus, movement of the fuel cam is reflected in movement of the control stops. The
                                             fuel cam has a roller at each end, and is connected through a pivoted link to the main control piston which is backed by
                                             calibrated springs. One of these two rollers runs on a reference surface in the body of the control unit, and the other
                                             on the track of the excess fuel lever, of which more is said later. The space at the back of the piston is connected to the
                                             engine down-stream of the throttle so that, as manifold pressure changes, the position of the control piston alters; this
                                             varies the fuel cam position, so causing the cam follower and control stops to take up a new setting to maintain the
                                             required fuel-air ratio.

                                                Since operation is by the difference in pressure across the throttle, the same full throttle stroke will be provided
                                             irrespective of the barometric pressure. Thus as the air becomes less dense, the mixture ratio applied to the engine
                                             would become progressively richer unless the fuel delivery were reduced proportionately. In the control unit, this is
                                             achieved by the use of a capsule responsive to changes in barometric pressure. The capsule carries a wedge which controls
                                             the final setting of the excess fuel lever in its warmed-up position, and so determines the inclination of the fuel
                                             cam track.

                                                For cold starting, additional fuel and air are required to overcome the friction of a cold engine and permit it to run
                                             at a fast idle; as the engine warms up, both require to be reduced in step. It must also be possible to drive the engine
                                             under any load during this period. A manual control is therefore provided which controls simultaneously the position


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