How To Test A Purge Valve: Tips & Tricks (Guide)

Last Updated on July 5, 2023 by Chase Manhattan

From many years in the industry, I’ve realized that the best way to understand proper testing procedure is to fully understand the functions behind the component that you’re testing.

With that being said:

The purge valve is an essential component in a vehicle’s Evaporative Emission Control System (EVAP System), which helps prevent harmful fuel vapors from being released into the atmosphere. In this comprehensive guide, we’ll cover various methods to test purge valves, with both handheld vacuum pumps and a multimeter, and we’ll make sure you know where the EVAP canister purge valve is located of course. We’ll also discuss common signs of a faulty purge valve and answer frequently asked questions related to the topic.

How To Test A Purge Valve By Hand

Testing a purge valve by hand is a quick and straightforward method to determine if it’s operating correctly; however, keep in mind that some applications have bypassed the EVAP canister entirely. To perform this test, follow these steps:

1. Locate the purge valve in your vehicle. It is typically found near the engine or intake manifold.
2. Disconnect the hose connected to the purge valve. This hose links the valve to the charcoal canister, which stores fuel vapors from the fuel tank.
3. Start the engine and check for vacuum at the disconnected port. There should be no vacuum present when the engine is cold, as the purge valve should be closed.
4. Allow the engine to warm up and check for vacuum at the port again. When the engine is hot, the purge valve should open and create a vacuum at the port.
5. If the vacuum is present or absent when it shouldn’t be, the purge valve may be faulty and require further testing or replacement.

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How To Test A Purge Valve With A Handheld Vacuum Pump

A handheld vacuum pump is a useful tool for testing the purge valve, as it can help identify any leaks or malfunctions in the valve. To test the purge valve using a handheld vacuum pump, follow these steps:

1. Locate and disconnect the purge valve as mentioned in the previous section.
2. Connect the handheld vacuum pump to the outlet port of the purge valve, which is responsible for releasing fuel vapors into the engine.
3. Pump the vacuum to create pressure between 20 and 30 Hg (inches of mercury). Maintain this pressure for 2 to 3 minutes and monitor the vacuum gauge.
4. If the vacuum pressure decreases during this time, the purge valve may be leaking and require replacement.
5. If the pressure remains stable, connect the purge valve to a power source (such as your car’s battery) to open it. The vacuum pressure should drop to zero when the valve is open, indicating that the purge valve is functioning correctly.

Test Purge Valve With Multimeter

A multimeter is an invaluable tool for testing electrical components, including the purge valve. There are two primary tests you can perform using a multimeter: the continuity test and the resistance test.

Continuity Test

The continuity test checks the integrity of the purge solenoid coil within the purge valve. To perform this test, follow these steps:

1. Disconnect the purge valve from your vehicle, ensuring the engine has been off for at least 30 minutes.
2. Set your multimeter to continuity mode, usually represented by a “sound wave” icon.
3. Place the multimeter probes on the power terminals of the purge valve.
4. If the multimeter emits a beeping sound, the coil within the purge valve is intact, and you can proceed to the resistance test. If no sound is heard, the coil may be damaged, and the purge valve likely needs replacement.

Resistance Test

The resistance test measures the resistance between the positive and negative terminals of the purge valve. To perform this test, follow these steps:

1. Disconnect the purge valve as mentioned in the continuity test.
2. Set your multimeter to Ohms (Ω) mode.
3. Place the multimeter probes on the power terminals of the purge valve.
4. Evaluate the results. A healthy purge valve should have a resistance between 14 Ohms and 30 Ohms, depending on the model. If the reading is outside this range, the purge valve may be faulty and require replacement.

Purge Valve Click Test

The purge valve click test is a simple method to identify a stuck closed purge valve. A healthy purge valve should emit a clicking sound when connected to a power source, such as a 12-volt battery. To perform the click test, follow these steps:

1. Disconnect the purge valve from your vehicle.
2. Use alligator clips to connect the purge valve’s power terminals to your car battery (one clip to the positive terminal and one to the negative terminal).
3. Listen for a clicking sound, which indicates the purge valve is opening. If no clicking sound is heard, the purge valve may be stuck closed and require replacement.

Symptoms of A Faulty Purge Valve

A faulty purge valve can cause several issues, including:

Performance Issues

A malfunctioning purge valve may cause loss of power, sluggish acceleration, and poor overall vehicle performance.

Rough Idling

A stuck open purge valve can cause rough idling due to high fuel combustion or an incorrect air-fuel mixture entering the engine.

Misfiring

Excess fuel vapors entering the engine due to a stuck open purge valve can lead to engine misfires.

Difficulty Starting

Both stuck open and stuck closed purge valves can cause difficulty starting the engine, as they disrupt the proper flow of fuel vapors which then effects the air-fuel ratio that enters the combustion chamber of the engine.

Poor Fuel Economy

A faulty purge valve can negatively impact fuel efficiency, as it may cause an incorrect air-fuel mixture in the engine.

Illuminated Check Engine Light

A malfunctioning purge valve often triggers the check engine light due to abnormal purge flow or other related issues.

Failed Emissions Test

A faulty purge valve can cause your vehicle to fail an emissions test, as it may release excess fuel vapors into the atmosphere. Additionally, most emission tests will fail you automatically if you have an illuminated check engine light.

Smell of Fuel Vapors

A leaking purge valve can cause a noticeable smell of gas fumes and fuel vapors around your vehicle.

Can You Drive With A Bad Purge Valve?

While driving with a bad purge valve is possible, doing so can lead to a variety of issues, including poor engine performance, increased emissions, and reduced fuel efficiency. It’s essential to address a faulty purge valve as soon as possible to avoid potential damage to your engine and other components.

Should You Clean Or Replace A Faulty Purge Valve?

While it is possible to clean a purge valve by spraying carb or MAF cleaner fluid into the inlet and outlet, this method may not always resolve the issue. In most cases, it’s best to replace a faulty purge valve to ensure proper function and prevent future problems.

How Do You Unclog A Purge Valve

To unclog a purge valve, follow these steps:

1. Disconnect the purge valve from your vehicle.
2. Spray carb or MAF cleaner fluid into the inlet and outlet of the purge valve.
3. Cover both ends, shake the valve well, and let the debris drain out.
4. Reinstall the purge valve and test its function. If the issue persists, consider replacing the purge valve.

What Is The Voltage To A Purge Valve?

The voltage supplied to a purge valve typically ranges from 12 to 14 volts, depending on the vehicle’s electrical system. This voltage is necessary for the solenoid valve within the purge valve to open and close properly, allowing fuel vapor to enter the engine when needed.