Understanding how diesel injectors spray can help you understand injector diagnosis better. Electromagnetic – or solenoid – injectors have a traditional coil, like you would see for a gas injector. The voltage that’s applied to the coil pulls the solenoid valve up. As it does, it allows the check ball to move up with it. Below the check ball is the inlet in the side of the injector for the high pressure fuel. The high-pressure fuel is applied to both the top and the bottom of the main injector servo-piston or nozzle.
Learn more about solenoid valves and how they work in this quick video.