Question 1

Pilot injection, also called split-shot injection, in HEUI B injectors is accomplished _______.

Accepted Answer

D

Question 2

Technician A says the measuring unit for the electrical signal to the injection control pressure regulator of a HEUI fuel system is reported as a percentage of duty cycle (%) on a scanner display of engine parameters. Technician B says the PWM signal is reported as time (in milliseconds). Who is correct?

Accepted Answer

The electrical signal to the injection control pressure regulator in a HEUI fuel system is typically reported as a percentage of duty cycle (%), which is a common way to represent PWM signals on diagnostic tools.

Question 3

Which of the following components multiplies oil pressure inside a HEUI injector?

Accepted Answer

The intensifier piston in a HEUI (Hydraulically actuated, Electronically controlled Unit Injector) system multiplies the oil pressure to create the high pressure needed to inject fuel into the combustion chamber.

Question 4

Which of the following conditions is indicated when engine oil contaminates the fuel tank of a vehicle with a HEUI engine?

Accepted Answer

A leaking injector external O-ring can allow engine oil to enter the fuel system, leading to contamination of the fuel tank.

Question 5

The maximum potential voltage supplied to a HEUI A or B injector is __________.

Accepted Answer

The answer of The maximum potential voltage supplied to a...

Question 6

While diagnosing the cause of a rough-running 2005 Ford Power Stroke engine, Technician A says that an incorrect injector calibration code will produce uneven cylinder contribution at idle. Technician B says that Gen II HEUI injectors do not use calibration codes. Who is correct?

Accepted Answer

Gen II HEUI injectors do not use calibration codes.

Question 7

Technician A says that it is important to remove and drain the oil reservoir for a HEUI high-pressure pump when changing engine oil so that the oil does not contaminate the clean engine oil. Technician B says that it is not required or practical to drain the oil reservoir or accumulator when changing oil. Who is correct?

Accepted Answer

Technician B is correct because it is generally not required or practical to drain the oil reservoir or accumulator when changing engine oil in a HEUI system. The system is designed to handle oil changes without needing to drain these components.

Question 8

While discussing the purpose of pilot injection, also known as split-shot injection, Technician A says HEUI injectors use it to reduce NOx emissions. Technician B says PRIME metering can reduce combustion noise. Who is correct?

Accepted Answer

Pilot injection is used in HEUI injectors to reduce NOx emissions by creating a more controlled combustion process. It also helps in reducing combustion noise, which aligns with Technician B's statement about PRIME metering.

Question 9

Which of the following forces do Gen II HEUI injectors use to physically move the spool valve in the injector control valve mechanism when it opens or closes?

Accepted Answer

Gen II HEUI injectors use oil pressure to move the spool valve in the injector control valve mechanism. The oil pressure is controlled by a solenoid that is actuated by an electrical signal, but the physical movement is driven by the oil pressure itself.

Question 10

Technician A says acoustic wave attenuation (AWA) fittings in the oil manifold of some Gen II HEUI engines reduce irregular combustion noise. Technician B says split-shot injection reduces combustion noise. Who is correct?

Accepted Answer

Both Technician A and Technician B are correct. Acoustic wave attenuation (AWA) fittings help reduce irregular combustion noise, and split-shot injection is a technique used to reduce combustion noise by injecting fuel in two stages.

Question 11

Consider a HEUI fuel system. When the injector pulse width remains constant and the injection control pressure increases, which of the following changes will take place?

Accepted Answer

Injection quantity is directly proportional to injection control pressure. As injection control pressure increases, injection quantity will increase.

Question 12

What change generally takes place when the length of the pulse width to an injection control pressure regulator (ICPR) is increased?

Accepted Answer

Increasing the pulse width to an injection control pressure regulator generally increases the injection pressure, as it allows more time for the pressure to build up.

Question 13

What does an above-normal increase in the duty cycle of the PWM signal applied to the HEUI ICPR indicate?

Accepted Answer

An above-normal increase in the duty cycle of the PWM signal applied to the HEUI ICPR typically indicates a worn-out high-pressure oil pump, as the system compensates for the lack of pressure by increasing the duty cycle.

Question 14

Technician A says an above-normal increase in the duty cycle of the PWM signal applied to the HEUI ICPR of a Cat C-7 engine indicates that the engine oil has thickened due to excessive soot loading. Technician B says a jumper plug in the wiring harness indicates to the engine's ECM that 10W-30 engine oil rather than 15W-40 oil is being used in the crankcase. Who is correct?

Accepted Answer

A jumper plug in the wiring harness indicates to the engine's ECM that 10W-30 engine oil rather than 15W-40 oil is being used in the crankcase.

Question 15

While considering ways to increase engine power output, Technician A says that using a special injection control pressure (ICP) sensor, which reports oil pressure as lower than the actual pressure, is an effective shortcut. Technician B says that using the modified ICP sensor signal will result in less fuel being injected. Who is correct?

Accepted Answer

Using a modified ICP sensor that reports lower oil pressure than actual would not effectively increase engine power output, as it could lead to incorrect fuel injection and engine performance issues.

Question 16

Consider an engine with a HEUI fuel system. Which of the following problems will most likely cause a hard start/prolonged cranking condition only when the engine is hot?

Accepted Answer

Leaking injector O-rings can cause a loss of fuel pressure, especially when the engine is hot, leading to hard starting or prolonged cranking.

Question 17

What is the measuring unit for the electrical signal to the ICPR of a HEUI fuel system?

Accepted Answer

The electrical signal to the Injector Control Pressure Regulator (ICPR) in a HEUI (Hydraulically actuated Electronically controlled Unit Injector) fuel system is typically measured in terms of the percentage of duty cycle (%), which indicates the proportion of time the signal is active.

Question 18

Technician A says that higher levels of detergents and antifriction additives are needed by HEUI engines to maintain stable injection control oil pressure. Technician B says that antifoaming agents are more important than additional antifriction and detergent additive for a smooth and efficient engine operation. Who is correct?

Accepted Answer

Antifoaming agents are more important than additional antifriction and detergent additive for a smooth and efficient engine operation.

Question 19

While diagnosing the cause of a hard start/prolonged cranking complaint, Technician A says that the high-pressure oil between the high-pressure pump and the injectors should stay pressurized for days. Technician B says the oil pressure to the injectors should quickly drop to zero when the engine is shut off. Who is correct?

Accepted Answer

The answer of While diagnosing the cause of a hard...

Question 20

When investigating the cause of frequent injector failures on a HEUI B engine, Technician A says a likely cause could be engine oil contaminated with dirt entering the engine through a leaking air filter. Technician B says that condition will not cause injector failure, because the oil is filtered before supplying the injectors. Who is correct?

Accepted Answer

Contaminated engine oil can cause injector failures in HEUI systems because the oil is used to actuate the injectors, and dirt can cause wear or blockages.

Quiz 12: Heui Injection Systems