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An essential part of your emissions control system, your vehicle’s vapor canister reduces the level of fuel that evaporates into the environment.



What is a Vapor Canister?

A vehicle’s vapor canister is an important part of its federally mandated emissions control system. When properly installed and maintained, the vapor canister reduces the amount of evaporated fuel a car or truck emits.

How do Vapor Canisters Work?

A fuel tank requires some type of vent to reliably dispense fuel to the engine. Without a vent, negative pressure builds up in the fuel tank and prevents fuel from flowing to the rest of the fuel system.

When the vehicle is parked, evaporated fuel makes it way through the vents and into the atmosphere. Vacuum canisters utilize activated charcoal to trap fuel in the system before it contaminates the environment. Some vacuum canisters feature one-way check valves to ensure water doesn’t contaminate the vehicle’s fuel tank.

Installation difficulty varies greatly based on how the vapor canister was designed and where the designers chose to mount it on your vehicle. On some vehicles, you may need to remove the fuel tank before being able to replace a malfunctioning vapor canister or its lines.

How are Vapor Canisters Made?

Vapor canisters on modern vehicles are often assembled with a plastic housing filled with activated charcoal. The vacuum canister may also have a purge valve and a vent solenoid, both of which may throw a check engine light if they malfunction.

Why do Vapor Canisters Fail?

  • Evaporated fuel saturates the activated charcoal, rendering the vapor canister ineffective.
  • The vapor canister purge valve may malfunction.
  • The vapor canister vent solenoid may malfunction.
  • The vapor canister lines become corroded, cracked, or broken.

What are the Symptoms Vapor Canister Failure?

  • Engine refuses to start.
  • Engine starts but dies after 5-20 minutes. The vehicle may start back up only to stop again shortly after.
  • Fuel pressure is below factory specifications.
  • Strong fuel smell near the vehicle.
  • Check engine light comes on and stays on.

What are the Implications of Failure?

  • Fuel vapor may start a fire, especially in enclosed spaces.
  • Your vehicle may run for a few minutes, then shut off as the flow of fuel to the engine stops.

Diagnosing a leaking valve cover gasket is as easy as popping your hood and having a look around. Once you confirm you need a new valve cover gasket, look to Pep Boys for the parts and service you need to get the job done right the first time.

If you have questions or concerns about vapor canisters or any of your vehicle’s components, come into your local Pep Boys where we can answer any question, help you find any part, or perform any vehicle service you might need.