Looking for a way to test your purge valve using a multimeter? Great you are in the right place!
In this ToolGaloreHQ.com blog, we will show you:
- Purge valve operating conditions
- All the equipment requirements
- The easy 4 step testing process
- And so much more!
Before we carry on and show you how to test a purge valve with a multimeter. Read the table below…
What you need to know about how to test a purge valve with a multimeter.
A purge valve is an important component in any car utilizing a combustion engine.
The Purge valve takes vapors from the fuel tank through an input hose. When the purge valve is operating correctly, it uses a 12 V supply from the car’s control computer. This control computer dictates the 2 main operating modes of your purge valve, namely: OPEN and CLOSE.
More detailed scientific modelling can be shown here.
The fuel vapors then go through the purge valve and move into the outlet hose. From here they go through the intake manifold and into the engine to be combusted as fuel.
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The beauty of this so called “recycling of fuel vapors”, is that it improves your cars air emissions. Plus adds a bit of much needed mileage.
So when people refer to a failed purge valve, what they are talking about is a purge valve that is either – STUCK OPEN, or STUCK CLOSE.
Stuck Open Purge Valve
A stuck open purge valve can lead to rough idling of the engine and engine misfiring. Also, it can lead to difficulty starting the engine (especially during winter).
The reason is because a stuck open purge valve creates an air vacuum leak in the intake hose.
This creates a sucking of extra additional air from the fuel tank. Which is more than is required, hence disrupting the engines operations.
The worst thing about a stuck open purge valve, is that you can go for weeks without noticing there is an issue.
Reason being it often does not register a code (which in-turn will provide an engine alert light) until the purge valve is completely damaged.
This is due to there being no blockage of air vapors from the fuel tank to the engine.
Stuck Closed Purge Valve
A stuck closed purge valve is best because in this case, an alert light will be activated immediately, letting you know there is a problem right away.
So if your engine starts rough idling, or you are having a tough time starting the car especially during winter. Then it is worth testing your purge valve with a multimeter.
Now let’s learn how to test purge valve with a multimeter…
Equipment You’ll need to test purge valve with multimeter
- Air Pump
- Purge Valve
- Multimeter and measurement probes
- Battery Power Supply (12V)
- 5/8 inch rubber hose with clamps
How To Test Purge Valve With Multimeter (4-Step Guide)
- Continuity Test
- Check The Ohm Meter Reading
- Mechanical Click Test
- Close Test
Step 1 – Continuity Test
To perform the continuity test, you will need to remove or disconnect the purge valve from the engine. This can be done easily by unscrewing the clamps for both the inlet and outlet hoses from the engine and fuel tank respectively.
Please ensure the car has been idle for at least 30 minutes.
If you are not comfortable doing this please contact a mechanic, or take your car into a service station.
Once you have the purge valve, set the multimeter to continuity mode.
Continuity mode is the mode whereby the multimeter will make an audible noise if you were to touch the two probes together.
Connect the probes to the power terminals of the purge valve. If you hear an audible sound, then the purge valve is working.
The reason for this is that most purge valves are solenoid purge valves.
Meaning that there is a copper/metallic coil inside the purge valve’s casing from the positive and negative power terminals.
If you do not hear an audible sound, then the purge valve is damaged and must be replaced.
Lets move onto the next test…
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Step 2 – Check the Ohm meter readings
Move the multimeter dial to be on the ohm-meter measurement.
Take the 2 probes and place them on the power terminals of the purge valve.
The multimeter should give you a reading. Typically a reading within the range of 14 to 30 ohms means that the purge valve is healthy.
If you have readings above or below this range there could be a problem with your purge valve and it might need to be replaced.
That is how you test a purge valve with a multimeter.
There are a few other tests you can perform below to really nail down the condition of your purge valve.
Step 3: Mechanical Click Test
This test checks whether your purge valve will operate when power is supplied to the terminals.
It’s very easy to setup and do.
Firstly, take your probes and connect them to your 12V battery terminal.
Secondly, connect the other ends of the probes to the terminals of the purge valve. If you hear a click, then your purge valve is operating correctly.
If there is no click, this means that the purge valve is damaged and must be replaced.
Step 3: Close Test
This test will tell you whether the purge valve is causing a vacuum leak or not.
Firstly – I want you to connect the 5/8 inch hose to the end of the purge valve that goes to the intake manifold of the engine. Make sure to tie the clamps.
Secondly - Connect the other side of the hose to the handheld vacuum pump.
Thirdly - Pump the handheld vacuum pump to about 20 or 30 in-Hg/mm-Hg.
Leave it there for about 2 to 3 minutes.
What you should see is that the vacuum pumps should not be leaking air (i.e. dropping in value). If this happens, it means that there is an air leak between your purge valve or the connection between the hose and purge valve is not solid.
If you see this, just make sure your hose is fastened correctly. Then run the test again. If it still fails – your purge valve is damaged.
If after 2 or 3 minutes the vacuum pumps value is roughly the same, take the probes and connect them to the 12V battery supply.
Then, connect the other side of the probes to the terminals of the purge valve.
If you hear a click and the vacuum pump quickly goes to 0. Then your purge valve is working correctly.
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Final Thoughts on Testing a purge valve with a multimeter
So now that you are familiar with the 4 key tests steps, bookmark this page so you can come back to it if you ever need this information again.
Word of note - just be sure you are familiar with the safety protocols of performing such a task. If you are not comfortable, the best would be to get a mechanic who can help you.