Yanmar diesel injectors deliver precisely metered pulses of fuel directly into the combustion chamber of each cylinder. Built to very tight tolerances, the injector pressurises the fuel to 2,800 to 3,000 pounds per square inch (psi) during injection. High engine hours can wear the injector and reduce output pressure. Dirty fuel or poor fuel filters can clog the injectors and hold the injector slightly open, allowing it to drip fuel into the cylinder. Leaky injectors can be identified by watching the exhaust. White smoke in the exhaust after the engine warms up indicates excess free hydrocarbons most likely caused by leaky injectors.
Start the engine and warm it up for 10 minutes. Turn the engine off.
Remove the injector line from the top of the injector with a wrench. Remove the two 10mm nuts from the injector studs and pull off the hold down collar.
Thread the injector puller tool onto the top of the injector. Slip on the injector puller tube, aligning the notches on the tube with the injector bleed tubes. Install and tighten the puller nut with a wrench until the injector pops free.
Slip the injector nozzle protector onto the injector tip. Slip the injector gasket onto injector tip. Insert the injector into the injector hole in the head. Install the hold down collar onto the injector hold down studs. Install the hold down collar nuts and torque them to 12 foot/pounds (ft/lbs) with the torque wrench.
Install the injector fuel line and tighten it down loosely. Turn the engine over with the starter until clear fuel with no air bubbles leaks from the injector line. Stop turning the engine over and tighten the fuel line fully.
Yanmar injectors are typically tough to remove. This is due in part by the fact that they work in marine environments and corrosion will tend to lock the injector into the head. Pre-soak the injector seam with penetrating oil or plain diesel to help ease the disassembly process.