Wobble Plate Pump System

Principles of Gasoline And Diesel Fuel Systems
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injection pump acts on the seat area of the pintle, forcing it outward

against a preloaded spring.

This spring, through its action on a spring

hanger, also returns the pintle to its seat, sealing the nozzle against

further injections or dribble when the line pressure is relieved at the

pump. When the pintle moves outward due to fuel pressure, an increasingly

larger orifice area is opened around the flow angle of the pintle.

(d) The hole nozzles have no pintle but basically are similar in

construction to the pintle type. They have one or more spray orifices that

are straight, round passages through the tip of the nozzle body beneath the

valve seat.

The spray from each orifice is relatively dense and compact,

and the general spray pattern is determined by the number and the

arrangement of the holes.

As many as 18 holes are provided in larger

nozzles, and the diameter of these drilled orifices may be as small as 0.006

in.

The spray pattern may not be symmetrical, as in the case of the

multifuel engine, where the spray pattern is off to one side so as to

deposit the fuel properly in the spherical combustion chamber. The size of

the holes determines the degree of atomization attained.

The smaller the

holes, the greater the atomization; but if the hole is too small, it will be

impossible to get enough fuel into the chamber during the short time allowed

for injection. If the hole is too large, there will be an overrich mixture

near the nozzle tip and a lean mixture at a distance from it.

Using

multiple holes in the injector tips usually overcomes both difficulties

because the holes can be drilled small enough to provide proper atomization

and in a sufficient number to allow the proper amount of fuel to enter

during the injection period.

c. Wobble Plate Pump System (figure 46 on the following page).

(1) General System Operation. The wobble plate pump system basically

is the same as the multiple unit injection system. The difference in the

systems lies in the injection pump. In a wobble plate pump, all of the pump

plungers are actuated by a single wobble plate instead of a camshaft that