Exam 11: Hydraulic Nozzles

Two technicians are describing measuring NOP (Nominal Opening Pressure). Technician A says that the liquid spray leaves the nozzle tip with sufficient velocity to penetrate the skin and cause serious injury. Technician B says that injector NOPs vary according to the type of nozzle and the manufacturer's specifications. Who is right?

Technician A says that servo-hydraulic injectors use hydraulically balanced nozzle valves. Technician B says that servo-hydraulic injectors require piezoelectric actuators. Who is correct?

Spray patterns can be first evaluated visually on a nozzle tester to determine whether the injector spray pattern is uniform and:

Technician A says that DI (Direct Injection) engines require greater capabilities to pressurize, atomize, and distribute fuel than do multi-orifice nozzles. Technician B says that older multi-orifice nozzles use four or five holes, whereas as many 13 can be found in newer designs used in heavy-duty applications. Who is right?

A diesel engine is misfiring with light smoke, especially at idle, along with excessive combustion noise. Which of the following is the MOST LIKELY cause?

What serves to mix and vaporize the coarse spray droplets?

Which of the following emissions would increase the most if a nozzle opening orifice were to become larger because of wear?

What type of nozzle is used only in IDI (Indirect Diesel Injection) combustion chambers?

Which of the following is NOT an effect of using higher NOP (Nominal Opening Pressure)?

Technician A says that injection lag takes place when the time between the actual beginning of injection (BOI) lags behind the time when fuel pressurization takes place. Technician B says that injection lag is caused by poor quality fuel with a low cetane number (CN). Who is correct?

Most pintle nozzles have an average NOP of:

Technician A says that the beginning of injection is the point when fuel delivery begins and is referred to according to the position of the crankshaft measured in degrees of crankshaft rotation. Technician B says to produce the sharp increase in pressure when the nozzle valve first lifts from its seat, it is necessary to ensure that the valve moves very slowly. Who is right?

Technician A says that some service facilities do test and repair the hydraulic nozzles used inside injectors because cleaning and rebuilding a nozzle in house is often more economical than replacing it. Technician B says when a problem with an injector is identified by the heavy-duty onboard diagnostics (HD-OBD) system or by using cylinder cutout and contribution testing, injectors are simply replaced with new or rebuilt parts. Who is right?

What is the purpose of a slight amount of fuel leakage around the nozzle valve and into the nozzle spring chamber?

When testing a fuel injection nozzle using a pop tester, what do you listen for?

When replacing an injector in an engine, Technician A says it is only important to make sure that the replacement injector belongs to the same family or model of engines. Technician B says it is important that for the replacement injector to have a spray pattern that matches the shape of the combustion bowl in the piston. Who is correct?

Which of the following is the typical nozzle opening pressure (NOP) of a new multi-orifice nozzle?

Which of the following is not a symptom of nozzle defects?

Technician A says that fewer, smaller spray holes in an injector tip will atomize fuel better than an injector with larger, more numerous holes. Technician B says that fewer, larger spray holes in an injector tip will produce better fuel atomization. Who is correct?

While discussing the purpose of a nozzle lift sensor, Technician A says that the sensor helps calibrate the amount of nozzle lift that an engine's injectors should have. Technician B says the sensor helps produce more precise injection timing. Who is correct?