What Is a Purge Valve?
The evaporative emission control system (EVAP) is used in automobiles to keep fuel vapors inside the fuel tank and prevent them from entering the surrounding environment. This crucial system usually functions without issue, but if any problems do surface, such issues can lead to a frustrating check engine light. In the EVAP, one of the most critical elements is the purge valve. It is also one most prone to degradation and failure. In this blog, we will discuss everything you need to know about purge valves so that you may have a better understanding of the EVAP as a whole.
The purge valve exists in the EVAP as an electrically-operated solenoid. When the engine is off, the purge valve rests in a closed position. Once the engine has been turned on and runs for a few seconds, the engine's computer sends a signal to open the purge valve, allowing vapors trapped in the charcoal canister to be released into the engine where they can be burned. The magnitude to which the canister releases these vapors is tightly regulated and falls in line with emission standards.
Purge valves connect to the engine intake manifold and EVAP system via a set of hoses. Occasionally, these hoses can fill with dirt and other debris over time. The valve itself is also prone to cracking when exposed to harsh environmental conditions, such as extreme heat and moisture. Moreover, some vehicle models contain valves that are more prone to leaking and remaining stuck in the open position. When this occurs, it is most noticeable after refueling and may cause the engine to feel rough for the first couple of seconds after ignition.
The purge valve testing procedure is straightforward and can usually be accomplished quickly:
- First, the tester should establish that the valve can properly open when a voltage is applied. To test this, connecting a 9-volt battery to the purge valve terminal and immediately listening for a click is recommended. If no click is present, that means the valve did not open properly in response to a voltage stimulus, or the wires were not connected to the terminal correctly.
- If the tester hears an audible click, they may connect a vacuum pump to the purge valve and begin to increase the pressure.
- With a properly functioning EVAP system, the vacuum pressure should continue to increase as the tester pumps. However, if there is a leak or crack, the pressure will immediately drop.
While it is generally safe to continue driving with a faulty purge valve as there is no immediate damage to the vehicle, it is important to replace it as soon as possible to prevent further EVAP harm. Replacing the valve through a mechanic is relatively cheap compared to other vehicle failures and will generally only cost between $70-$200, most of which accounts for labor. However, they may be much more expensive in luxury cars with more advanced digital sensors in the EVAP system. Some owners choose to replace the valve themselves, but this requires a fair amount of mechanical expertise and a strong knowledge of the vehicle's under-hood component structure.
If you are looking to replace a purge valve and need a reputable source, there is no better alternative to ASAP Aviation Unlimited. Owned and operated by ASAP Semiconductor, we offer customers cost savings and rapid lead times on an inventory of over 2 billion ready-to-purchase components for a variety of industries. Additionally, as an AS9120B, ISO 9001:2015, and FAA AC 00-56B accredited company, we regularly subject our inventory to several quality-assurance tests in order to screen for any potential issues before shipping. Get started on the purchasing process with an RFQ today to experience the ASAP difference.
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