New Holland CX720 Repair Manual page 1858

POWER PRODUCTION - FUEL AND INJECTION SYSTEM
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Fuel Delivery Cycle
Reference (A) - Bottom dead centre / Fuel in
Reference (B) - Spill port closure / Fuel Pressurized
Reference (C) - Spill port opening / Fuel delivery ends
(A) With the plunger (1) at the bottom of the stroke, fuel flows into the barrel through the spill port (2) and fills the
space above the plunger.
(B) As the plunger (1) rises, the spill port in the barrel (3) is covered and the fuel is trapped. This is the point of port
closure. The continued upward movement of the plunger pressurizes the trapped fuel until the delivery valve (at the
base of each high-pressure injection line) is lifted from its seat. High- pressure fuel is transmitted through the line to
the injector and injection takes place through the injector nozzle.
(C) Injection stops when the upper edge of the helix (4) uncovers the lower edge of the spill port. Pressure escapes
to the fuel gallery. The drop in pressure causes the injector to close and injection to stop. After fuel delivery ceases,
the plunger continues to the top of the stroke and is returned by a spring for the next cycle.
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