Evap fault

[sterling]

My daughters Fabia 1.4 mpi 8v head gasket finally gave up and replaced it at weekend. All went well apart from a really lumpy tick over and misfire which she said was there before gasket went. There has always been an engine management light on so thought I would look further. If I remove evap valve altogether and join the pipes together engine runs perfect. But then I get a fault code that says evap purge valve open. I bridged the plug to the evap with a peice of wire and so far light has not come back on. Question is ...is this going to cause any problems to engine or is dangerous?   I have replaced the evap valve 3 times since she has owned it but after a short time light comes back on?

[sepulchrave]

If the purge valve doesn't open then the fuel tank becomes pressurised with petrol vapour while the car is stood.

[sterling]

By taking the valve out and joining the pipes is that the same as the valve being open?

[sepulchrave]

19 minutes ago, sterling said:

By taking the valve out and joining the pipes is that the same as the valve being open?

 

Yes, it's perfectly safe like that.

[Breezy_Pete]

It seems likely to me that this fix of deleting the purge valve is not solving the real problem, but I'm not sure what that underlying fault might be.  What was the exact fault code number?

Have you checked the brake servo pipe for cracks and leaks, that's always worth a look?

 

Here's some background info on the purge valve/EVAP system: https://www.samarins.com/glossary/purge-valve.html

The Fabia implementation doesn't have the second solenoid valve labelled Vent control valve, I'm not sure what takes its place, perhaps just a one-way valve to let air in when pressure inside is lower than outside.

 

[LB123]

Strangely enough half an hour ago I was sitting by the roadside with the charcoal cannister in my hands in my ongoing quest to find an 'airleak'.

For the 1.4 16v car and I'm guessing all the petrol Fabs there are two bayonet connectors on top of the cannister, one going to the filler pipe and one going to the purge valve in the engine bay. Only valve in the system is the purge valve. (On my car its closed when the ignition is off). No solenoid or valve on the cannister, just a 5+mm hole in the bottom of it, next to the mounting bolt. No Valve in this hole on mine. I can suck and blow through it! Seems that the fuel tank vapour space is sealed at the filler cap but can passively suck and blow through this hole in the bottom of the charcoal cannister at will. So leaves the petrol fumes in the charcoal when blowing out and clears them back into the system when fresh air is sucked in with the purge valve open.

 

I was going to ask on here if this was normal. But two of the highly regarded posters above don't seem to have come across this. Certainly a significant airflow if you bypass the pipes round the purge valve.

 

Quote

I bridged the plug to the evap with a peice of wire

Not sure that is a good move.

 

Edited 9 October, 2018 by LB123

[Breezy_Pete]

^ Nice work. 

[LB123]

Next time you have a chance can you look and see if yours is the same. Easily visible without any dismantling.

[Breezy_Pete]

This is my Polo, but looks identical as I'd expect:

 

[sterling]

Does anyone know the correct part number for evap on Fabia 1.4 mpi 8 v.      Trying to buy one from flea bay but when I put vehicle details in it says not suitable?

[Breezy_Pete]

Always good to include year and engine code when looking for part numbers, but I think they're the same on all petrol Fabias 6Q0906517, item 19 here:

https://skoda.7zap.com/en/cz/fabia/fab/2003-225/1/133-133005/

According to the site I use to find superseding part numbers, this has not been superseded by any other number, so parts with the same core 9 characters but with a letter suffix are not necessarily compatible. https://oemwolf.com/oem-parts/6q0906517.html If it had been superseded, it would say so on this page, and link to a similar page for the superseding number.

Edited 10 October, 2018 by Wino

[sterling]

Thanks for the reply I am trying to find via my purchase history the part number of the last one I fitted I think it was the same with *A* at the end but will check. Something I did notice when I checked the removed valve it does not shut completely with no power and it was full of sooty carbon. So I may have to blow out and clean pipes

[sepulchrave]

24 minutes ago, sterling said:

Thanks for the reply I am trying to find via my purchase history the part number of the last one I fitted I think it was the same with *A* at the end but will check. Something I did notice when I checked the removed valve it does not shut completely with no power and it was full of sooty carbon. So I may have to blow out and clean pipes

 

That'll be the problem, it should shut completely when disconnected.

[Kusai]

On 08/10/2018 at 20:26, sterling said:

My daughters Fabia 1.4 mpi 8v head gasket finally gave up and replaced it at weekend. All went well apart from a really lumpy tick over and misfire which she said was there before gasket went. There has always been an engine management light on so thought I would look further. If I remove evap valve altogether and join the pipes together engine runs perfect. But then I get a fault code that says evap purge valve open. I bridged the plug to the evap with a peice of wire and so far light has not come back on. Question is ...is this going to cause any problems to engine or is dangerous?   I have replaced the evap valve 3 times since she has owned it but after a short time light comes back on?

If the carbon canister is broken from inside , it will keep destroying the valve every time , cuz the activated carbons  will keep moving from the canister to the valve and that will keep destroying it .