Diesel Engine Fuel Injector Service

Regardless of the nozzle type, injectors should
• Discharge cleanly without “after-dribble,” which tends to collect in the cylinder between cycles.
• Atomize fuel for rapid combustion.
• Direct the spray into the far reaches of the cylinder, but without impinging against the piston or chamber walls.

Most malfunctions are caused by carbon buildup on the tip, which distorts the spray pattern and can sometimes stick the needle or pintle in the open position. Automatic injectors can be tested with the apparatus shown in Fig. 5-23. Similar tests can be performed on unit injectors by loading the pump cavity with fuel and applying force to the pump plunger.