NAPA Fuel Systems & Fuel Delivery 2

Question 1

In a returnless fuel system, how is fuel pressure regulated?

Accepted Answer

By varying fuel pump speed based on engine demand

Answer

By a mechanical pressure regulator at the fuel rail

Answer

By a pressure relief valve inside the fuel tank

Answer

By adjusting the fuel injector duty cycle

Question 2

What is the stoichiometric air-to-fuel ratio for a gasoline engine?

Accepted Answer

14.7:1

Answer

12.5:1

Answer

9.0:1

Answer

16.5:1

Question 3

Which sensor primarily calculates air mass in a speed-density fuel injection system?

Accepted Answer

Manifold Absolute Pressure (MAP) sensor

Answer

Mass Airflow (MAF) sensor

Answer

Throttle Position Sensor (TPS)

Answer

Crankshaft Position Sensor (CKP)

Question 4

What does a large positive long-term fuel trim (LTFT) value indicate?

Accepted Answer

The ECM is adding fuel to compensate for a lean condition

Answer

The engine is running rich

Answer

Fuel pressure is too high

Answer

The fuel injectors are oversized for the engine

Question 5

What is the function of the fuel return line in a conventional fuel injection system?

Accepted Answer

To return excess pressurized fuel and heat back to the tank

Answer

To deliver extra fuel during wide-open throttle

Answer

To recirculate fuel continuously through the filter

Answer

To relieve vapor lock by venting fuel vapors

Question 6

What is 'vapor lock' in a fuel system?

Accepted Answer

Fuel vaporizing inside the lines before reaching the engine, causing fuel starvation

Answer

A solenoid valve that secures the fuel filler cap

Answer

Ice formation inside the fuel line restricting flow

Answer

A blocked vent tube creating negative pressure in the tank

Question 7

What is the purpose of the inertia switch found in some vehicles' fuel systems?

Accepted Answer

To shut off the fuel pump automatically in the event of a collision

Answer

To modulate fuel pump speed based on engine RPM

Answer

To prevent the fuel pump from overheating during extended idling

Answer

To reduce in-tank fuel pump operating noise