Abstract: A known type of fuel injector has a discharge passage which can be closed off by a tip sealing valve and provision for circulating fuel in the vicinity of the discharge passage. In order to test that the passage is completely closed by the tip sealing valve, the passage is closed, and the injector is blocked off from the supply and return lines while remaining full of fuel. An attempt is made to introduce more fuel into the injector and, if a significant amount can be introduced, it means that there is leakage from the injector, presumably through the discharge passage.

Abstract: A fluid injector particularly for injecting fluid into a furnace comprises a housing structure having inlet and outlet ports; a pair of fluid connections and means defining passageways for fluid between the ports and respective ones of the fluid connections; and valve means for controlling the flow of fluid along said passageways; a body assembly including an elongate tubular portion having provision for receiving a nozzle at its outer end; a pair of fluid connections and means defining passageways for fluid between each of the fluid connections and said outer end of the tubular portion; said housing structure providing a support for the body assembly and including fluid pressure means for displacing the assembly relative to the housing between a first position, in which the fluid connections on the body assembly are coupled to respective fluid connections on the housing structure, and a second position, in which the fluid connections on the body assembly are disconnected from the fluid connections on the hou