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...http://www.google.de/patents/US4559815?utm_source=gb-gplus-sharePatent US4559815 - Testing device for fuel injectors
