Learning, Multimeter,

How to Test Purge Valve with Multimeter

The purge valve forms part of the Evaporative Emission Control (EVAP) system in a vehicle. The mechanism helps prevent the fuel vapors generated by the engine from escaping into the environment or back into the car. It temporarily stores them in a charcoal canister. The valve also helps control the volume of fuel vapors that are ultimately “purged” from the charcoal canister.

In modern automobiles, the system is an electronic-operated solenoid connected to the engine’s power. The purge valve gradually powers up as soon as the ignition is turned on, but the EVAP system also doesn’t work when the engine is off.

There can be times when the system malfunctions, which harms your car’s health! It is handy when you know how to test a purge valve with a multimeter. Apart from this, we will also be discussing the following points: 

  • The consequences of canister purge valve going bad
  • Is a purge valve supposed to click?
  • Can a bad purge valve result in a misfire

Ways to Test the Purge Valve Through a Multimeter

Aptly named, a multimeter is a handy device that can measure voltage, resistance, and electric current.

The resistance between the terminals must be checked to test the purge valve.

The procedure can differ depending on the car model, but the basic steps remain the same.

Mentioned below are the common steps that can be used to test the purge valve that’s part of an EVAP system: 

  1. Pinpointing The LocationThe first thing to ensure is that the engine is turned off for at least 15 to 30 minutes. After that, try locating the purge valves of the vehicle. Ideally, it can be found behind the silencer or the muffler and positioned on top. That is the EVAP charcoal canister, and the purge valve is inside it. For more help locating the system, try searching in the car’s manual or looking up the model on the internet with engine graphics.
  2. Readjusting the CablesAfter locating the purging valve, you will see that there is a 2-pin harness that is connecting to the device. The next step is disconnecting and reconnecting them with the multimeter’s adapter cables, which usually come with the testing kits. They are also available to purchase separately. The terminals of the purge valve should be connected to the cables of the multimeter.
  3. Testing the final step is measuring the resistance. The ideal levels should be between 22.0 ohms and 30.0 ohms; anything higher or lower will mean the valve needs replacement. It can be done on the spot if you have a spare one; otherwise, if you want to take it into the shop, then be sure to reconnect the harness cables as previously.
How to Test Purge Valve with Multimeter

How Do I Know if My Purge Valve Is Bad?

There are many symptoms that a malfunctioning EVAP system emits. Look out for:

Engine Light The engine controls the purge solenoid, and if anything fails, the engine light will turn on. When higher or lower levels of purged vapors are detected, error codes, including P0446 or P0441, are displayed. We recommend taking the vehicle to a repair shop if you notice the above indicators.

Problems with Engine If the purge valve has failed to close, it may negatively affect the air-to-fuel ratio due to vapors’ leakage into the nearby environment. The engine will react to the change, leading to difficulty in powering up or rough idling.

Lower Gas Mileage When the EVAP system doesn’t work effectively, it will inevitably decrease the gas mileage. Instead of being stored in the purge valve, the fuel vapors will start seeping into the environment, causing increased fuel combustion.

Poor Performance in the Emissions Test The canister EVAP is responsible for redirecting the fuel vapors back into the engine. It helps in preventing toxic fumes from escaping into the environment. In the case of a faulty solenoid, it wouldn’t be able to control the fumes, and it will fail emission tests.

Ruined Gaskets Since the vapors will not be able to pass when the valve malfunctions, the pressure will start building up. Over time, it will become so intense that it can blow out rubber seals and gaskets. Subsequent consequences will be oil leakage, which can spill out of the emission system into the main engine causing severe damage. The most common reason for than ideal performance of the purge valve is the pieces of carbon or foreign materials getting stuck, which results in the mechanism remaining partially closed or open. It will require a replacement or cleaning.


Is a Purge Valve Supposed to Click?

The short answer to the question is – yes! The purge valve usually makes a clicking or ticking noise. However, it should be unnoticeable inside the car, with the windows closed. If it starts getting too loud and can be heard inside the vehicle, it can cause concern. The solenoid should be checked.

One possibility is that the purge valve has started leaking vapors into the engine when refueling. It will result in a rough start and problems, as mentioned above.

How to Test Purge Valve with Multimeter

Can a Bad Purge Valve Cause Misfire?

 A faulty purge valve can result in misfires if the situation has been overlooked for some time. As the vapors start collecting excessively in the EVAP system or the charcoal canister, the valve will fail to open on time.

If the process continues over time, the fumes will seep into the engine cylinders, resulting in an abnormal amount of fuel and vapors getting burned. This combination will cause the engine to choke and then misfire. (1)


Final Verdict

The solenoid valve is an important component of a car. If you notice any problems listed above, the vehicle should be brought in immediately for repairs. If you want to test out the canister yourself, you can follow the steps with the multimeter, and the device will let you know if you have a malfunctioned valve! (2)

Since we’ve presented you with how to test the purge valve with a multimeter, you may also want to check. You may want to check a guide about the best multimeter and decide which fits your testing needs.

We hope this learning article helps you. Good luck!

References

(1) EVAP system – https://www.youtube.com/watch?v=g4lHxSAyf7M (2) solenoid valve – https://www.sciencedirect.com/topics/earth-and-planetary-sciences/solenoid-valve

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About Sam Orlovsky

AvatarCertifications: B.E.E.
Education: University Of Denver - Electric Engineering
Lives In: Denver Colorado

Electrical engineering is my passion, and I’ve been in the industry for over 20 years. This gives me a unique ability to give you expert home improvement and DIY recommendations. I’m not only an electrician, but I also like machinery and anything to do with carpentry. One of my career paths started as a general handyman, so I also have a lot of experience with home improvement I love to share.

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