CEI Evaporative Emission Control Systems

Question 1

What is the primary purpose of an evaporative emission control (EVAP) system?

Accepted Answer

To prevent fuel vapors from escaping into the atmosphere

Answer

The EVAP system captures and stores fuel vapors from the fuel tank and fuel system, preventing them from venting directly into the atmosphere and contributing to hydrocarbon emissions.

Question 2

Which component in the EVAP system stores fuel vapors before they are purged into the engine?

Accepted Answer

Charcoal (activated carbon) canister

Answer

The activated charcoal (carbon) canister adsorbs and temporarily stores fuel vapors from the fuel tank until conditions allow them to be drawn into the engine and burned.

Question 3

What is the function of the purge valve (purge solenoid) in an EVAP system?

Accepted Answer

It controls airflow from the canister to the intake manifold

Answer

The purge valve, controlled by the PCM, opens to allow stored fuel vapors in the charcoal canister to be drawn into the intake manifold and burned during normal engine operation.

Question 4

A vehicle sets a P0442 diagnostic trouble code. What does this indicate?

Accepted Answer

EVAP system small leak detected

Answer

P0442 is defined as 'Evaporative Emission Control System Leak Detected (small leak),' indicating the EVAP system cannot maintain pressure, typically caused by a leak equivalent to a 0.020-inch orifice.

Question 5

What does the fuel tank pressure (FTP) sensor measure in an EVAP system?

Accepted Answer

Pressure or vacuum inside the fuel tank

Answer

The fuel tank pressure sensor monitors the pressure (positive) or vacuum (negative) inside the fuel tank, providing the PCM with data needed to perform EVAP leak detection tests.

CEI - Certified Emission Inspector Practice Test

CEI - Certified Emission Inspector Practice Test

CEI Evaporative Emission Control Systems