The information and schematic are from the web site Pintle Injector Blog.
A pintle injector is a variable area injector consists of a movable pintle, an annular nozzle and the central pintle nozzle. Propellants from the center and annular nozzles collide near the pintle tip.
Either fuel centered or oxidizer centered approaches can be used in design. In oxidizer centered approach, there is a moving pintle at the center that controls the oxidizer and an annular gap on the outside of the inner body that controls the fuel.
All the pintle injector diagrams I have found show that moving the pintle tip could close the central pintle nozzle, but wouldn’t affect annular gap on the outside of the inner body. The pintle tip does not cover the annular gap. By enlarging the pintle tip and extending the outer edge of the annular gap, moving the pintle could regulate and shut off the flow of both the fuel and oxidizer.
Is this what is done in the Merlin engine?
How many pintle injectors are in the Merlin combustion chamber?
Does the Merlin gas generator use pintle injectors?