Here are four different methods for those looking for ways to test a purge valve without a vacuum pump.
Even though it is easy to test the purge valve with a vacuum pump, you might not have a vacuum pump every time. On the other hand, finding and buying a vacuum pump isn’t easy. Considering all this, learning a few alternative ways to test a bad purge valve might not be the worst idea in the world. So, in this article, I hope to teach you four simple techniques that you can use to test a purge valve without breaking a sweat.
In general, to test a purge valve without a vacuum pump, use one of these four methods.
- Purge valve click test.
- Purge valve stuck open test.
- Test the continuity of the purge valve.
- Test the resistance of the purge valve.
Read the respective step-by-step guides for each method in the below article.
4 Easy Methods on How to Test Purge Valve without Vacuum Pump
Method 1 – Purge Valve Click Test
In this method, you’ll check the purge valve’s clicking sound. When the purge valve gets power, it opens up and releases a clicking sound. If you can detect this process correctly, you’ll be able to determine the condition of the purge valve.
Quick Tip: The purge valve is part of the vehicle’s EVAP system and helps the fuel-vapor burning process.
Things You’ll Need
- 12V battery
- A few alligator clips
Step 1 – Locate and Remove the Purge Valve
First and foremost, locate the purge valve. It should be located in the engine bay. Or it should be close to the fuel tank. Disconnect the mounting bracket and other connectors. Regarding other connectors, there are two hoses and one wiring harness.
One hose is connected to the charcoal canister. And the other is connected to the intake. The wiring harness supplies power to the purge valve and connects to thideoe two power terminals of the valve.
Step 2 – Connect the Purge Valve to the Battery
Then, connect two alligator clips to the battery’s positive and negative terminals. Connect the other ends of the alligator clips to the purge valve terminals.
Step 3 – Listen
A properly working purge valve will emit a clicking sound. So, listen carefully while connecting the alligator clips to the valve. If you cannot hear any sound, you are dealing with a bad purge valve.
Method 2 – Purge Valve Stuck Open Test
This second method is a bit old-fashioned, but it is an excellent way to test the purge valve. The best thing about it is you don’t have to remove the purge valve from the vehicle, and no tools are required.
Note: You already know the location of the purge valve; hence I’m not going to explain it here.
Step 1 – Disconnect the Canister Hose
First, disconnect the hose that comes from the charcoal canister. Remember, you shouldn’t disconnect the hose that comes from the intake. Keep it intact during this testing process.
Step 2 – Start the Vehicle
Then start the vehicle and allow it to idle. This is an important step, allowing the vacuum to be applied to the purge valve.
Quick Tip: Remember to apply the parking brake during this testing process.
Step 3 – Disconnect the Wiring Harness
Next, locate the wiring harness and disconnect it from the purge valve. When you disconnect the wiring harness, you don’t have to be concerned about any electrical wiring issues (in this testing process, you are not testing the wire connections).
Step 4 – Place Your Thumb on the Canister Hose Port
Now wet your thumb and place it on the canister hose port. If the valve is working correctly, you won’t feel anything.
However, if you feel any vacuum, the purge valve is faulty and needs to be fixed.
Method 3 – Continuity Test
Continuity is one of the best ways to test the purge valve. If something inside the valve is broken, it will not show continuity.
Things You’ll Need
- Digital Multimeter
Step 1 – Disconnect the Purge Valve from the Vehicle
First, locate the purge valve and disconnect it from the vehicle. Remember to disconnect the two hoses and the wiring harness.
Quick Tip: The vehicle should be switched off during this process.
Step 2 – Set the Multimeter to Continuity
As I mentioned earlier, you are going to check continuity. Hence, set the multimeter’s dial to the continuity symbol. It is a triangle that has a vertical line. Also, connect the red jack to the Ω port and the black one to the COM port.
After you set the multimeter to continuity, the multimeter will emit a beep sound when you connect the two probes. This is an excellent way to check the multimeter.
Step 3 – Connect the Multimeter’s Probes
Then connect the multimeter probes to the two power terminals of the purge valve.
Step 4 – Evaluate the Results
The purge valve is working fine if you can hear a beep sound. If it isn’t, the purge valve is faulty.
Method 4 – Resistance Test
The resistance test is the same as method three. The only difference is, here, you are measuring the resistance.
The resistance of a purge valve will be between 14Ω and 30Ω. You can test the purge valve according to those numbers.
Things You’ll Need
- Digital Multimeter
Step 1 – Disconnect the Purge Valve from the Vehicle
Locate the purge valve and disconnect the mounting bracket first. Then, disconnect the two hoses and the wiring harness.
Pull out the purge valve.
Step 2 – Set the Multimeter to Resistance Settings
Then, turn the multimeter’s dial to the Ω symbol on the multimeter. If needed, set the resistance range to 200Ω. Remember to connect the red jack to the Ω port and the black one to the COM port.
Step 3 – Connect the Multimeter Probes
Now connect the multimeter probes to the purge valve’s power terminals.
And note down the resistance valve.
Step 4 – Evaluate the Results
If the resistance value is between 14Ω and 30Ω, the purge valve works properly. The purge valve is broken if you are getting a completely different value.
How Do I Know the Purge Valve is Bad?
There are quite a few symptoms for identifying a bad purge valve. These symptoms might occur regularly or occasionally; you should never ignore them.
- Check engine light is ON.
- Trouble starting the vehicle.
- Failing emission test.
- Damaged spark plugs or gasket.
- Engine misfire.
If you detect any of the above symptoms, it might be time for a test. However, the cause of the above symptoms might not be the purge valve’s fault in every situation. So, testing is the best way to eliminate any doubts.
Initiate easy testing methods such as click test or stuck open test. Or get a digital multimeter and test the purge valve for continuity or resistance. Either way, these methods are excellent when you cannot find a vacuum pump. Even if you have a vacuum pump above methods are easy to execute rather than using a vacuum pump.
Important: If needed, don’t hesitate to get help from a professional for the above testing process.
Take a look at some of our related articles below.
- How to test purge valve with multimeter
- Where is the engine ground wire located
- How to test coil pack with multimeter
Video References
PistonShack
Barbour’s Auto Help
Dorman Products
Mercedessource