Yhy does Lucus injector pump pass fuel to crankcase ?

Last primary fuel filter change on the Perkins 4108 I switched the fuel back from "return to tank" to "go to engine" but forgot to shut of the electric feed pump for a while. Used to be that the pump would stop with engine not running but this time put about a gallon of fuel in the crank. The electric polishing pump just kept passing fuel through the injector pump and into the oil pan. Is there a diagram for the Lucas CAV pump?