three way valves forming a fuel cut - off valve are arranged across respective injection pipes connected to injection nozzles associated with preselected cylinders of the engine . in a first valve position , the three way valves connect the injection pump body or bodies of the fuel injection pump to the respective injection pipes , and in a second valve position , they connect the injection pump body or bodies to a lower pressure zone in the pump . preferably , the fuel cut - off valve is pneumatically operated for high speed valve position changing action .