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Discussion Starter #1
Hi All,

I am getting a check engine light with P0455 (Evap Emission System Leak Detected - Large Leak")

I replaced the gas cap and the N80 valve. Also discovered that the intake manifold actuator links arms were broken and replaced those.

I do have a smoke machine that I have used on older cars for carb issues and to find AC leaks. Seems like it would come in handy here but I do not know how to use it on a vehicle like the Treg. Any (detailed) guidance appreciated.

Thanks,
 

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Discussion Starter #2
Discovered crack in one of the hard vacuum lines to intake. Taped it up for now. Hopefully that fixes her.
 

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Discussion Starter #4
Grrrrr! Light came back on.

So, any guidance on smoke test proceedure for Treg appreciated. Where should I inject smoke, anything need to be clamped or switched (via vagcom).

Thanks.
 

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Discussion Starter #5
So, I injected smoke into fuel fill and also from n20 line back toward tank. No unexpected smoke trails. I did make a discovery, could it be that simple? The retaining ring from original cap was sitting at bottom of filler neck. New cap does not have this ring. It may have been keeping cap from fully seating. Wishful thinking or fortuitous discovery, I will soon find out.
 

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Discussion Starter #6
Well, the problem returned. With low expectations I thus payed $35 for the factory cap at the stealer. Guess what? It seems to have fixed the issue, no error in the last two days.

The Autozone cap was identical to the AdvanceAuto cap and both were triggering "check gas cap". Seal on factory cap seems to be a stiffer rubber than the aftermarket. Will keep you posted but looking good so far.
 

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Discussion Starter #8
Should have kept my mouth shut. Check cap message just returned. Yes, "how to" for Treg smoke test would be helpful.
 

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Discussion Starter #10
Yes, but in Treg I think that means using VCDS to close or open certain switches. May even need to jumper something? Also hearing it may entail dropping the tank?
 

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Discussion Starter #12
Hmm. Here is the latest. I pumped in more smoke to line from evap valve leading back toward tank. As before, it makes it way out vapor canister. I then pinched off line to canister. At this point smoke makes its way to fuel tank. Nothing leaking past the cap as confirmed when removing / reinstalling cap. But here is where things get interesting/ troubling. While I can not see any smoke I can hear hissing under car. I'm not even sure where fuel tank is on this beast, presumably under rear seat and hidden by plastic covers. Seems like that is where noise is coming from. Smoke could be dispersing too much to see.

What's next? Dropping the tank? That sounds expensive / time consuming.

Open to ideas. Next step is probably the dealer. If they can diagnose cause of this and my bearing/tire/other noise I will then need to decide if 16 year old Treg is worth fixing.
 

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Discussion Starter #14
Yeah! I am 90% certain I have found the leak.

Lifted rear seat, cut carpet and pulled fuel pump covers. The one on driver side (with fuel filter) definitely has slightest fuel odor. Pumped in more smoke while clamping hose. Can hear the hiss and see slight wisps if smoke. Grabbed my electronic AC sniffer. Sure enough, beep beep beep at hose connection.

Filter is original at 117k miles. I just Ordered new filter / pump assembly and gasket.

20190911_104143.jpg
 

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Discussion Starter #16
One thing leads to another.

Replaced the filter assembly. Cleared codes and waiting for tests to cycle. Put in some fuel, 20 seconds later she dies. Appears to be a bad fuel pump. Pump for both left and right on order.
 

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One thing leads to another.

Replaced the filter assembly. Cleared codes and waiting for tests to cycle. Put in some fuel, 20 seconds later she dies. Appears to be a bad fuel pump. Pump for both left and right on order.
VW found that when they replaced the fuel pump flanges under recall, they had a good chance at having to replace the fuel pumps.

Those plastic fuel hoses get brittle with age. Working theory is that the tubes were still OK until they were moved to put in the new fuel filter. The plastic fuel lines then develop leaks. The fuel is then being pumped around the inside of the fuel tank and escaping back into the tank. The end result is that there is not enough fuel pressure at the engine for the engine to run.
 

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One thing leads to another.

Replaced the filter assembly. Cleared codes and waiting for tests to cycle. Put in some fuel, 20 seconds later she dies. Appears to be a bad fuel pump. Pump for both left and right on order.
I replaced both of my fuel pumps. Had them die on me in the dessert while towing. Well it worked the next day, just that they couldn't keep up with amount needed for towing.
 
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