Question 1

Diesel fuel with a cetane number (CN) of 50 or greater has which of the following characteristics?

Accepted Answer

A

Question 2

Technician A says that placing a fuel heater in a filter housing is the best way to prevent wax and ice crystals from restricting fuel flow. Technician B says that ethanol can be used to dissolve wax and prevent water from crystalizing in fuel filters. Who is correct?

Accepted Answer

Placing a fuel heater in a filter housing is an effective method to prevent wax and ice crystals from forming and restricting fuel flow, especially in cold conditions. Ethanol is not typically used for this purpose.

Question 3

What effect does gasoline contamination have on diesel fuel?

Accepted Answer

Gasoline contamination in diesel fuel lowers the flash point, making it more volatile and increasing the risk of premature ignition.

Question 4

What effect does increasing fuel temperature have on diesel engine operation?

Accepted Answer

Increasing fuel temperature reduces its density, leading to a lower mass of fuel being injected into the engine, which can reduce power output.

Question 5

Which of the following is the result of water contaminating fuel?

Accepted Answer

Water contamination in fuel can lead to rusting or corrosion of fuel system components due to the presence of water, which promotes oxidation and corrosion.

Question 6

Technician A says straight vegetable oil (SVO) can be burned in a diesel engine without causing any long-term problems for engine durability. Technician B says SVO will damage injectors. Who is correct?

Accepted Answer

Straight vegetable oil (SVO) can cause long-term problems in diesel engines, such as damaging injectors, due to its higher viscosity and different combustion properties compared to diesel fuel.

Question 7

Technician A says that adding a little gasoline to diesel fuel will help a diesel engine start faster in cold weather, reduce combustion noise, and improve power output. Technician B says that adding gasoline to diesel fuel will make starting worse, increase combustion noise, and accelerate fuel system wear. Who is correct?

Accepted Answer

Adding gasoline to diesel fuel can harm the engine by reducing lubrication, increasing wear, and causing poor combustion, leading to increased noise and starting issues.

Question 8

Technician A says that 2-D fuel provides the most power and best fuel economy for an on-highway diesel engine. Technician B says that 1-D is the best fuel for producing power and good fuel economy. Who is correct?

Accepted Answer

2-D fuel is a type of diesel fuel that has been treated with a hydrogenation process. This process removes the sulfur and other impurities from the fuel, which results in a cleaner burn and improved fuel economy. 1-D fuel is a type of diesel fuel that has not been treated with a hydrogenation process. It is less refined than 2-D fuel and contains more sulfur and other impurities. As a result, 1-D fuel produces more emissions and has worse fuel economy than 2-D fuel.

Question 9

Technician A says that diesel fuel's low volatility is why so many diesel fuel pump islands appear to have a lot of spilled fuel. Technician B says that fuel spills at diesel pump islands are more common than those at gasoline pumps because truck drivers are careless when refueling. Who is correct?

Accepted Answer

Diesel fuel's low volatility means it evaporates less quickly than gasoline, leading to more visible spills at diesel pump islands.

Question 10

Which of the following properties does B5 diesel fuel have?

Accepted Answer

B5 diesel fuel contains 5% biodiesel, which is derived from biological sources such as vegetable oils or animal fats, and 95% petroleum diesel.

Question 11

Which color is fresh, good-quality 2-D diesel fuel when it is commercially retailed?

Accepted Answer

Fresh, good-quality 2-D diesel fuel is typically clear or slightly amber in color when commercially retailed.

Question 12

Technician A says that coolant is used to heat fuel in fuel-water separators. Technician B says that electrical heating elements keep water and wax from plugging the filter in a fuel-water separator. Who is correct?

Accepted Answer

Both Technician A and Technician B are correct. Coolant can be used to heat fuel in fuel-water separators to prevent wax formation, and electrical heating elements are also used to prevent water and wax from plugging the filter.

Question 13

Technician A says that adding alcohol to diesel fuel is a good practice because it keeps fuel from waxing when it is cold and it improves engine starting. Technician B says wax in fuel should be removed at the refinery because it causes owners to make complaints about low power in hot weather. Who is correct?

Accepted Answer

Adding alcohol to diesel fuel is not a good practice as it can cause damage to the fuel system and engine. Wax in diesel fuel is typically managed with additives or by refining processes, but it is not primarily a cause of low power in hot weather.

Question 14

The temperature at which wax crystals begin to form in diesel fuel is referred to as its _______.

Accepted Answer

The cloud point is the temperature at which wax crystals first start to form in diesel fuel, causing it to appear cloudy.

Question 15

Which of the following methods is best suited to treating diesel fuel that contains free water while minimizing any potential damage to the fuel system?

Accepted Answer

Coalescence is a method that separates water from diesel fuel effectively without adding substances that could harm the fuel system.

Question 16

A primary fuel filter will typically have ___________.

Accepted Answer

The answer of A primary fuel filter will typically have...

Question 17

Technician A says that the primary filter helps extend the life of the secondary filter. Technician B says that the primary filter is located between the engine's high-pressure injection system and the secondary filter. Who is correct?

Accepted Answer

The answer of Technician A says that the primary filter...

Question 18

Technician A says that a float sensor can be used in a filter housing to measure the level of water, to determine when the filter should be drained. Technician B says that a probe in the bottom of a fuel filter, which measures the difference between the conductivity of water and fuel, is used to switch on the water-in-fuel warning lamp. Who is correct?

Accepted Answer

Both Technician A and Technician B are correct. A float sensor can measure water levels in a filter housing, and a probe can detect water in fuel by measuring conductivity differences.

Question 19

Technician A says that primary filters typically use chemically treated paper filter media with a micron rating of more than 10 microns. Technician B says that synthetic filter media is used to separate bound, or coalesced, water from fuel inside a primary filter. Who is correct?

Accepted Answer

Technician A is correct because primary filters often use chemically treated paper with a micron rating of more than 10 microns. Technician B is also correct because synthetic filter media can be used to separate coalesced water from fuel in primary filters.

Question 20

Which of the following is the best factor to use when determining whether a fuel filter should be replaced?

Accepted Answer

Restriction measurement directly indicates the filter's condition and effectiveness, providing a clear signal for replacement.

Quiz 8: Diesel Fuel and Low Pressure Fuel Systems