Delivery valve

The delivery valve is one component of the injection pump.
The delivery valve performs the following two functions.
(1) Backflow prevention: If fuel flows backward from the injection nozzle side when the plunger is lowered, the time lag from the start of the next pump to the start of nozzle injection increases.
To prevent this, fuel backflow is prevented by cutting off the delivery chamber from the injection pipe once fuel pumping is completed.
(2) Suck-back (dribble) prevention: Although the seat surface lowers until it touches the delivery valve seat, because fuel may still be sucked back from the injection pipe during this period, the delivery valve reduces pressure inside the pipe by improving nozzle injection cutoff, in turn preventing fuel dribble.
Because dribble will cause combustion to occur even during the late combustion period, it can result in malfunctions such as carbon formation and increased exhaust gas temperatures.