pr0xZen

After a long time with intermittent starting issues and throwing too many parts at it, I finally figured it out. And as I haven't seen this anywhere else (couldn't find it atleast), I thought I'd share. Overall its a rather qiock fix and simple job, requiring only basic tools and a soldering iron. If you're considering changing che EVAP purge valve anyway, you could very easily save $100+ this way.

Sympthom: Cranking freely on starter, not firing, intermittent occurance. Most times when warm, but occationally when cold. Some times, when engine fully warmed up, it would "instantly" fire, but cut after a fraction of a second and just continue cranking on starter. A slight dab on the gas would make it fire, but it would catch on and build up very slowly. Runs and drives semingly fine afterwards.

Cause: busted EVAP purge valve - internal breaks causing intermittent contact. PN VAG: 077133517C / BOSCH: 280142308

After having seen a thread on cleaning the EVAP purge valve on a different forum, I decided to open it up an inspect it before throwing more parts at it. I supported the valve on the end of a table so as to not put too much force on the in/out ports. I then used a slim flathead screwdriver and a hammer, tapping it down and working my way around the edge where the two parts of the outer shell is joined, to crack the glue holding the outer shell together. Once I had it open, I extracted the internal mechanism and cleaned the mesh filter in the smaller port with break cleaner. I suggest doing this over a sheat of paper or similar, as if any internal pieces are broken off, they 'll most likely remain inside the housing, but can easily get get lost.

Then, I applied 12 volts to the terminals, and observed that the valve was operating sporadically and unevenly. I proceeded to carefully bend back the tabs holding the switch mechanism together, so I could separate it.

On the underside of the bar going across the top, there's attached a thin copper shim that is part of the electromagnetic operation. This had several breaks in it. I was able to solder this shim back together (taking care not to solder the shim stuck to the rest of the mechanism). Put it back together, tested operation again and it proper function had been restored. Clean off any carbon dust, check the rubber o-ring seal that goes around the port in the "lid" of the outer housing. Assembly is disassembly reversed. I used epoxy glue to glue the outer shell back together, RTV silicone could also be used.

Pictures of the purge valve internals, the tabs to bend (cafully) to disassemble the internal valve, and the broken copper shim:

EVAP purge valve internals



EVAP pruge valve - tabs



EVAP purge valve, copper shim breaks

jcman

Good to see you back too.
I have seen a few posts on small in-line filters for this valve to keep debris out of it, I'll have to search it.

pr0xZen

Good to be back

hopefully you could relay the inline screens here, as I guess they would be valuable information and very relevant to topic. Also, in my case, I managed to break the internal screen on the engine side before I fully understood the ups and downs of this unit, so an inline screen would be useful