Abstract: An acceleration pump used in conjunction with an automatic cold start air-fuel mixture supply device, comprising a suction-operated diaphragm, and pressure regulating valve means controlling the communication of engine suction to such diaphragm, movement of such valve means being controlled both by thermostatic means responsive to engine temperature and by a control beam responsive to diaphragm movement.

Abstract: A manifold depression responsive fuel pump has its fuel outlet connected to an automatic cold start air/fuel mixture supply device, and a movable stop, which limits movement of the pump diaphragm to enlarge the fuel chamber, has its position controlled by the engine temperature responsive thermostatic control mechanism of the cold start device. The pump diaphragm carries a shut-off valve opposite the pump fuel inlet. Fuel is pumped into the cold start device by the pump when the carburetter throttle valve is opened before the engine has warmed up to normal working temperature. The movable stop is moved towards the pump fuel inlet, as the engine warms up, and seats the shut-off valve in that fuel inlet when the engine has warmed up to its normal working temperature so that the pump does not function to pump fuel into the cold start device once the engine has warmed up to its normal working temperature.

Abstract: An oxygen sensor is fitted to the exhaust pipe of a spark ignition internal combustion engine so that it projects into the exhaust gas stream. Its output is connected to a comparator circuit which has its output connected to the actuator of a variable airflow controller which controls airflow through an air supply passage which is connected to the fuel supply jet of an air valve carburetor between the fuel metering orifice and the fuel discharge nozzle of that carburetor. The comparator circuit emits an output when the oxygen sensor detects that the ratio of the air/fuel mixture fed to the engine by the carburetor is either richer or leaner than the stoichiometric ratio. The output from the comparator circuit drives the variable air flow controller in the appropriate direction to tend to return the ratio of the air/fuel mixture fed by the carburetor to the engine towards stoichiometry. An auxiliary air supply passage may be connected to the induction passage downstream of the throttle valve.

Abstract: An internal combustion engine cold start device has an air valve which co-operates with a valve seat to vary the cross-sectional area of an gas supply passage upstream of a plug valve in the passage. The air valve is urged towards the valve seat by a coil spring and a plunger, which is urged towards a stop by another coil spring, provides a resilient abutment for the air valve which limits movement of the air valve away from its valve seat. The plunger is urged away from its stop, against the action of its coil spring, by manifold depression which is fed to the plunger bore by a short straight pipe.