How to Bypass Evap Canister (Purge Control Valve)?

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Want to know how to bypass the Evap canister? Read till the end to find out the easiest method to do so. 

An Evap canister is a crucial part of the emission control system in your vehicle. Its primary function is to gather and hold the fuel vapors from the fuel tank and stop them from being released into the atmosphere. 

But in some instances, you may need to bypass the Evap canister, which basically means disconnecting or removing a faulty Evao canister. If you are not an auto-savvy person, the process might be a tad tricky for you. 

I will go through every detail regarding the Evap canister and its functionality in this article. We will also discuss how to bypass it and whether it’s safe to do so or not. Let’s get going.  


What is an Evaporative Canister?

An evaporative canister, also known as a charcoal canister, is a component of the internal combustion engine inside your vehicle. Its primary function is to hold fuel vapors generated in the fuel tank and contain them from being discharged into the environment. 

The vapors coming from the fuel tank go inside the evaporative canister through a tiny hose pipe. When the engine is running, a small valve inside the canister, known as the purge control valve, permits the vapors to be sucked out and into the engine’s intake manifold, where they burn off alongside the ordinary fuel. It reduces pollution and increases fuel efficiency.

The evaporative canister is usually found beneath the hood, near the fuel tank. It’s a crucial part of the vehicle’s evaporative emissions control system, which helps to keep hazardous hydrocarbons out of the atmosphere. If the canister fails to function effectively, it can lead to various difficulties, including poor engine performance and excessive emissions.

How Does It Work?

The Evap canister is filled with activated charcoal and holds the fuel vapor inside while the vehicle is shut down. As soon as you start the car, the Engine control module regulates the operation of the purge control valve based on the engine speed, load, and temperature. 

When the purge control valve is opened, the Evap canister’s fuel vapors are sucked into the engine and burned alongside the air/fuel mixture, resulting in lower emissions and enhanced fuel efficiency. When the purge control valve is closed, fuel vapors are kept out of the engine and returned to the Evap canister.

Why Bypass Evap Canister?

There are several reasons why you may need to bypass the Evap canister. Let’s discuss some of them:

1. Faulty Purge Valve

A faulty purge control valve might cause problems with the vehicle’s evaporative emission control system, leading to a failed emissions test. Any issues with the purge control valve must be thoroughly diagnosed and repaired to ensure that the vehicle operates correctly and efficiently.

2. Blocked Nozzles 

It is essential to regularly clean the vapor storage outlet nozzles because they are frequently exposed to the environment and can quickly become clogged with dirt and mud. It will help ensure that the gas fuel can flow through them properly.

3. Worn out Charcoal

The Evap canister contains activated charcoal that absorbs the fuel vapors. But over time, the charcoal starts losing its freshness and porosity. As the vehicle keeps moving, the charcoal particles crush each other and canister walls, eventually turning into a powder that can’t hold the vapor. 

If the charcoal has been exposed to moisture from condensed vapor, or fuel from the tank, it can lose its porosity. As a result, the vapor vent gets clogged, deteriorating your engine performance and fuel efficiency. 

4. Damaged Charcoal Filter

The fuel filters at the entry and exit ends of the vapor storage canister may wear down over time, allowing the charcoal to enter the purge control valve. It can contribute to a canister malfunction.


How to Bypass Evap Canister? Step-by-step Guide

Here are the steps you need to take to bypass the Evap canister:

  • First, you need to remove the faulty canister. Mark the two lines on top and one on the bottom of it.
  • Spray some WD40 on the edges and use pliers to hold and twist the top ones. 
  • Use the same methods for the bottom line. If it’s hard to come off, use some lubricant and then use the pliers to twist. The canister will come off quickly as the vacuum line will go loose. 
  • Next, you need to undo the purge control valve attached to the line on the side and to a nut in the bottom. Pull it on the side and use the appropriate wrench to unscrew the nuts. 
  • Locate the engine vacuum line under the air vent module and unplug it at the end.  
  • Next, secure a cap in the assortment kit that fits the vacuum ports.
  • You must loop the rest of the hose pipes to keep the vacuum intact. 
  • Connect the feed and fuel vapor return lines in a loop to prevent the engine base from being clogged with fuel vapors and emitting a fuel odor. It will ensure that the fuel system is in good working order.
  • To complete the Evap bypass, Locate the rubber line on the engine vacuum line, twist it around, and connect both ends of the wire to the ports to secure them.

For more details, check out this tutorial


Should You Bypass Evap Canister?

Usually, It is not advised to bypass a vehicle’s Evap canister. It is an essential part of a vehicle’s emissions control system since it helps to decrease the amount of toxic vapor emitted into the atmosphere. Bypassing the EVAP canister can result in higher emissions and difficulties with the vehicle’s fuel system. Doing this may also lead to a failed emission test, which can cause a heavy financial penalty. 

If you are having problems with your EVAP canister, you should have it thoroughly diagnosed and repaired by a professional mechanic. Let them identify the source of the problem and make the required repairs to guarantee that your car runs adequately and efficiently.


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