Abstract: A fuel supply passage has connections to two sources of fuel, and valves responsive to pressurization of the connections inhibit circulation of fuel from one of the sources to the other source.

Abstract: The reciprocating plunger reciprocable in the pump cylinder of a distributor type diesel fuel injection pump is helically splined to an index ratchet gear that is also operatively associated with a pawl detent whereby the index ratchet gear is rotatable in only one direction. The plunger has a discharge slot on its outer peripheral surface which registers with one of the plural discharge ports opening from the pump cylinder and the plunger controls the covering and uncovering of a fuel inlet port to the pump cylinder. Upon a pump stroke of the plunger, the index ratchet gear is rotated so that the next adjacent tooth is brought into alignment with the pawl detent to then prevent its rotation in the opposite direction during the suction stroke of the plunger.With the index ratchet gear thus fixed, the plunger is thus rotated on the suction stroke so as to align the discharge slot with the next adjacent discharge port.