Largest Fuel Injector Pintle cap selection available. We have every cap from a wide range of injectors for top feed, side feed and hose-end injectors. A pintle cap is the small replaceable piece of the injector designed to protect the fragile pintle end of a fuel injector. Over time as pintle style injectors have been replaced with a disc style injector. The newer pintle cap is more of an o-ring retainer.