Modern cars have many parts and systems that must work in sync for the vehicle to function correctly. Otherwise, you would see the check engine light appear, which means there is some problem with the car or some of its parts.
Sometimes, it can be difficult even for the best car mechanics to determine what could be wrong with a car. There are many things to look into, but one of the often overlooked parts is the purge valve. Although small, a malfunctioning purge valve can easily cause your car to malfunction or even refuse to turn on.
In today's guide, I will tell you everything you need to know about the purge valve, how to test purge valve with multimeter, and why this is an important part to test. I will also mention the best way to do a continuity and resistance test using a multimeter and how to perform manual tests with a vacuum pump or battery.
If you want to learn how to test purge valve with multimeter, stick around for the rest of the guide!
What is a Purge Valve?
The purge valve, or rather the canister purge valve solenoid, is part of all cars with a combustion engine. It is part of the EVAC or the Evaporative Emission Control System. It is connected to the Powertrain Control Module or PCM. What it does is help reduce the emissions coming from the vehicle while preserving as much fuel as possible.
Understandably, this is a part that is extremely important for the car. Suppose you have a faulty purge valve on your vehicle. In that case, you will have difficulties turning it on, accelerating while driving, or even driving in general. Moreover, you will also see that you run out of fuel faster than before.
If any of these things have happened to you recently and you have a check engine light constantly on, you need to look closer at the purge valve. You can either take it out and inspect it yourself or take the car to the shop and have it inspected and repaired. The canister purge valve is often easy to replace and costs little, so you should not dread taking your car to the mechanic's shop.
How to Test Purge Valve with Multimeter
If you want to test a purge valve because you suspect it is faulty, you can do the testing in a few different ways. I recommend using a multimeter, a device you can use to measure the current, resistance, and voltage of many car parts, including the purge valve.
If you have a multimeter, you can do a continuity test along with a resistance test to check whether you have a faulty or healthy purge valve on your hands. You can also do mechanical click and vacuum pump tests if the valve needs further testing.
I will discuss these four testing methods below, so stick around to learn more about what it takes to test a purge valve:
Continuity Test with Multimeter
Doing a continuity test with a multimeter is very easy. The first thing you need to do is locate the purge valve in your car and remove it. Ensure the car has been off for at least 30 minutes before you do so, so the car engine has time to cool down.
Once the valve is removed, you can get your multimeter. It should come with two probes you need to attach to the multimeter on one end and the valve power terminals on the other. But before you connect the probes to the power terminals, ensure you set the multimeter to continuity mode.
If the valve is healthy and there is no problem with the coil, the multimeter will make a beeping sound as soon as you attach the probes to it. Suppose there is no sound, even with the attached probes and the multimeter set according to the instructions. In that case, your purge valve is likely faulty and needs replacement.
Resistance Test with Multimeter
Another purge valve test you can do with a multimeter is the resistance test. It is similar to the continuity test mentioned above, with one simple difference in the multimeter settings.
To test purge valve for resistance, you first need to remove it from the car. That means disconnecting all the clams and having the purge valve as an isolated car part.
Then, you can set the multimeter to resistance mode or ohms, usually marked with the Omega letter of the Greek alphabet. Turn the multimeter to ohms, connect the probes on one end to the device and on the other to the purge solenoid valve, and start the test.
On the multimeter, you should get a number telling you the resistance of the valve. If it is between 15 and 30, the purge solenoid valve is okay, and you can put it back into the car. If the number is below 14 or above 30, you should get a replacement purge valve and add it to your car instead of the bad purge valve.
Extra Purge Valve Tests
Even though it is best to test a purge valve with a multimeter, I also recommend doing a few mechanical tests to ensure everything is okay with the valve. For example, the mechanical click test can tell you if the purge valve opens and closes correctly. Then, the air leak test can tell you whether there is a problem with the hose going to the valve.
It is very important to know how to do these tests. So, let's discuss them in greater detail and see what the purge valve is supposed to do when faced with a 12V battery or handheld vacuum pump:
Mechanical Click Test
For the click test, you need a 12V battery and some probes you can attach on one end to the battery and on the other to the solenoid purge valves. In this case, the valves do not need to be removed from the car beforehand.
Find the EVAP purge valve and connect the terminals to it first. Then, attach the other end to the battery. You should hear a clicking sound as soon as you are done attaching. It is basically what the valve does when the PCM sends the command to open or close.
The clicking sound should tell you that you have a healthy purge valve. Suppose there is no clicking even after you attach the positive and negative power terminals. In that case, you have a damaged purge valve on your hands and need to replace it with a new one as soon as possible.
Vacuum Leak Test
Finally, there is the vacuum pump test that you can do on the purge valve to see if there is any air leak between it and the fuel tank. So, the first thing to do is remove the valve from the car and disconnect it from all other car parts.
Next, grab a 5/8 outlet hose. On one end, attach it to the purge valve. On the other end, attach it to a vacuum pump. Ensure everything is tight so there is no air leakage between parts. If you need to, use rubber seals to reinforce the connections.
It would be best to use a handheld vacuum pump as that allows you to pump air through the outlet hoses easily. Pump about 30 in-Hg and leave the pump for a few minutes. Check the air levels to see if there is any air leakage. If there is, you need to replace the purge valve.
If there is no air leakage, you can do one more thing. Use the terminals to attach probes and a 12V battery to the purge valve. As soon as you connect the probes, you should see the air pressure drop and go to zero. That means the purge valve clicks and allows air to move in the hose.
Common Issues and Troubleshooting
Most purge valves are so well made that they never suffer any damage. You can use a car for years without getting a faulty or broken purge valve. But sometimes, the purge valve can suffer damage even if you try protecting it to the best of your ability. Here are the common issues with purge valves and how you can repair them:
Stuck Open Purge Valve
If you ever experience a problem starting your car, you may have a stuck open purge valve that you need to repair. When the purge valve is stuck open, it allows the air to move through it and go into the fuel tank, which results in extra air in the fuel.
You would need to remove the bad purge valve and replace it with a new one so that you can control the air going to the fuel tank. That way, you will eliminate the car starting problems.
Stuck Closed Purge Valve
The purge valve can become stuck open, but it can also become stuck closed. When the purge valve is stuck closed, the fuel vapor is trapped and has nowhere to go. As a result, the check engine light comes on, and the engine starts rough idling.
The best thing would be to test the purge valve and see if you can repair it or need to replace it altogether. A replacement will immediately eliminate all problems, so it is wise to choose that option.
Purge Valve Connection Problem
Finally, the purge valve can come undone if your car suffers a crash or significant bump. When in perfect position and working properly, the purge valve is connected to the PCM system, which tells it when to open and when to close. If disconnected, the PCM system cannot send any instructions to the valve, which will cause the car to malfunction.
In this case, you can fix the problem with a simple readjusting of the purge valve. If that does not help, consider testing the valve before deciding whether to put it back in or replace it with a new part.
Thank you for reading this detailed guide on all things purge valves. I hope you have learned what the purge valve is and how to test it with a multimeter should you suspect it is malfunctioning. A timely diagnosis and replacement of a faulty purge valve can help you get your car back to its former glory while also helping you save a fortune on gas!
If you suspect your purge valve is not working as it should, do not hesitate to follow the instructions provided in this guide to test the valve. If you find it is not working properly, replace it immediately to eliminate the possibility of further damaging the car.
As always, share your thought on this guide in the comments below. All feedback is much appreciated!