When we arrived at the shop, Jim and Lyle had a set of injectors to process from a customer’s four cylinder engine, they’re the green tipped injectors on the left. All four of them passed the pressure test, but the guys showed us an injector that failed a pressure test recently. Believe it or not, the constantly flowing injector on the right was in a car that was still being driven. A leaking injector not only wastes fuel, it also can damage an engine by washing oil off the cylinder wall and allowing metal-on-metal wear.