Fuel pump plunger

Claim 1

In an injection pump having a cylinder with a fuel inlet, an injection pump-fuel pump plunger reciprocally mounted and axially rotatable in said cylinder from a first angular position to a second angular position, and said pump plunger having a circumscribed groove of varying axial width thereabout, the groove having a scroll edge proximate one end of said plunger, said scroll edge increasing in distance from its closest point of approach to the one end of said pump plunger for less than the circumference of said plunger and remaining at substantially equal distance from said one end for substantially the rest of the circumference, so that said fuel inlet is selectively blocked by said pump plunger for a first length of reciprocal travel of said pump plunger with said pump plunger at said first angular position and blocked for a proportionally longer length of reciprocal travel of said pump plunger with said pump plunger at angular positions between said first angular position and said second angular position whereby pressure may be developed in said cylinder at said one of said pump plunger upon reciprocation thereof, said pump plunger further defining an axial slot communicating said circumscribed groove with said one end, said axial slot positioned on the periphery of said pump plunger at the point of closest approach of said scroll edge to said one end; the improvement comprising a bleed-off groove formed in said pump plunger and selectively communicating said fuel inlet with said circumscribed groove at angular positions between a position at least greater than said first angular position and a position equal to said second angular position of said pump plunger; said bleed-off groove relatively shallower than said circumscribed groove and positioned between said scroll edge and said one end.