Fuel tank ventilation purge valve

[Pond]

I changed the purge valve on my M54 yesterday, as it was throwing a fault and the solenoid was knackered.
Fault has gone, but the new valve makes a loud 'ticking' noise at idle. It's very annoying!
The noise does come and go, but more come than go. It goes if I rev the engine aswell, then re-appears at idle.

My question is...does anyone know what the actual purpose of the purge valve is, and should it be used when the engine is running normally?

 

[ChrisD]

I changed the purge valve on my M54 yesterday, as it was throwing a fault and the solenoid was knackered.
Fault has gone, but the new valve makes a loud 'ticking' noise at idle. It's very annoying!
The noise does come and go, but more come than go. It goes if I rev the engine aswell, then re-appears at idle.

My question is...does anyone know what the actual purpose of the purge valve is, and should it be used when the engine is running normally?

The purge valve allows fuel tank vapour to be captured in the carbon canister using the connection to the intake manifold to draw the vapour from the fuel tank under controlled conditions - usually at idle. The system uses the O2 sensors to detect the amount of fuel vapour present and control the valve accordingly. This is why you will find it activating and deactivating cyclically. When the system is purging and the fuelling indicates rich it will continue. When the system sees a lean condition indicating no fuel vapour present it will switch off. The valve operates at a frequency of around 2~3Hz, which is what you are hearing.
My vehicle makes the same noise when purging and I agree it’s a bit annoying. I have thought about exchanging the valve but I suspect the issue is more to do with the noise being transmitted along the fairly rigid vapour line to the fuel tank which is in fairly close proximity to the driver. I have reconciled the minor annoyance with being able to quickly detect that the system is operating correctly, if noisily.
BTW - the purge valve is not a fuel tank vent valve - that’s something else for a different discussion.
I hope I’ve captured the essence of what’s going on. Any further questions, let me know.

 

[Pond]

The purge valve allows fuel tank vapour to be captured in the carbon canister using the connection to the intake manifold to draw the vapour from the fuel tank under controlled conditions - usually at idle. The system uses the O2 sensors to detect the amount of fuel vapour present and control the valve accordingly. This is why you will find it activating and deactivating cyclically. When the system is purging and the fuelling indicates rich it will continue. When the system sees a lean condition indicating no fuel vapour present it will switch off. The valve operates at a frequency of around 2~3Hz, which is what you are hearing.
My vehicle makes the same noise when purging and I agree it’s a bit annoying. I have thought about exchanging the valve but I suspect the issue is more to do with the noise being transmitted along the fairly rigid vapour line to the fuel tank which is in fairly close proximity to the driver. I have reconciled the minor annoyance with being able to quickly detect that the system is operating correctly, if noisily.
BTW - the purge valve is not a fuel tank vent valve - that’s something else for a different discussion.
I hope I’ve captured the essence of what’s going on. Any further questions, let me know.

Wow thanks for that. Great description.
I was assuming my new valve was faulty, but it may just be (very) noisy. It sounds like a really noisy tappet!
I will see how things go when I use the car (only tested it in the garage so far). The valve I bought was a cheap copy from eBay!

 

[ChrisD]

Wow thanks for that. Great description.
I was assuming my new valve was faulty, but it may just be (very) noisy. It sounds like a really noisy tappet!
I will see how things go when I use the car (only tested it in the garage so far). The valve I bought was a cheap copy from eBay!

You’re welcome! My noisy purge valve is the original OEM fitment. I think it has got noisier over time but I can’t be sure. It is worth checking that the rubber isolation mount for the valve is fitted correctly and that the blue (usually!) vapour line is not touching the bodywork anywhere. If you do manage to quieten it down I’d be grateful to hear how you did it. As mentioned, I’ve no great desire to go fixing something that isn’t really broken on my car - just a little bit annoying.

 

[Pond]

You’re welcome! My noisy purge valve is the original OEM fitment. I think it has got noisier over time but I can’t be sure. It is worth checking that the rubber isolation mount for the valve is fitted correctly and that the blue (usually!) vapour line is not touching the bodywork anywhere. If you do manage to quieten it down I’d be grateful to hear how you did it. As mentioned, I’ve no great desire to go fixing something that isn’t really broken on my car - just a little bit annoying.

Mine is just the solenoid "chattering", as if I grab hold of the valve, or wiggle it on it's mount it makes no difference. It's not vibration, or resonance. But obviously it vibrates because of the chattering!

One way I found to quieten it down is to disconnect the electrical plug. It's silent then! Defeats the object though.