fuel evap system removal?

**nthusiastt** · 11-06-2010 03:49 PM

Hey guys,
Anyone know how to remove or modify to make quite a bit smaller the rear fuel evap system and pump? I'm cutting out the rear tire tub and the system runs along the tub.. Anyone done this before?

**nthusiastt** · 11-06-2010 04:15 PM

Also planning on, while the rear subframe is dropped, replacing the subframe bushings. Anyone have any thoughts on the solid ones from 034? Wondering how much of a rattle box my wagon would be with the solid rear bushings? (Have really heavy spring rates in the rear)

**salts** · 11-06-2010 04:40 PM

I took my evap system completely out. I am just having VAST deactivate the fault codes. Should not be a problem for you. Car will run fine without you will just have a CEL if you dont de-activate the fault codes.

**J-b5** · 11-06-2010 04:42 PM

how do you vent the tank without the evap system in place?

**1sadavant** · 11-06-2010 06:47 PM

Easy, just did this the past weekend. The canister is there to absorb excess vapors and retain overflow from the fuel tank if you overfill it. All you need to do is remove the canister and route the three lines together with fuel hosing and a t-fitting. You don't get a CEL this way because you are keeping the circuit closed. Been running this way for 500 miles with no problems. Gollygwagen (chuck) has been running his tracked and daily driven s4 like this for the past year without problems. So I think it safe to say this canister is only for emissions.

**nthusiastt** · 11-07-2010 12:50 AM

^^ Awesome info, thanks guys! Could you perhaps draw out a quick diagram in paint or something so I can get a visual? Thank you!

**gearhead1186** · 11-07-2010 01:07 AM

Originally Posted by salts

I took my evap system completely out. I am just having VAST deactivate the fault codes. Should not be a problem for you. Car will run fine without you will just have a CEL if you dont de-activate the fault codes.

i did the same. any plans on passing readiness or paying your way thru?

**nthusiastt** · 11-07-2010 01:16 AM

^ No worries on emissions. I live in nomans land. No emissions required.

**1sadavant** · 11-07-2010 09:14 AM

Originally Posted by nthusiastt

^^ Awesome info, thanks guys! Could you perhaps draw out a quick diagram in paint or something so I can get a visual? Thank you!

No diagram needed, it's really intuitive. There are 2 lines off the evap canister with a ID of 3/4"; and one that is 3/8". Just go to auto store and purchase a fuel injector hose. (I think I bought 3/8"; Dayco fuel injector hose and it was roughly 2 or 3 feet in package) However, since I didn't have ID of the hoses that attached to the canister, if I were you I would buy 3/8 and 3/4 id hose.

Problem with only 3/8 inch id hose is that it only will fit one of the three lines well. The other 2 lines are the same id and I had to route the fuel hose inside the hard line instead of slipping it over top and clamping. Also, with 2 different sized fuel hoses you may run into a problem with the t-fitting, either it being only 3/8's and the larger hose being to large or buying a larger t-fitting and the 3/8"; fuel line is too small. However, just buy clamps larger than .5"

Please let me know if this is not clear.

**nthusiastt** · 11-07-2010 02:25 PM

Thanks for the help man, I'll pick up some of that hose and take a peak at it. I'm betting after taking a closer look at it It'll make more sense.

**salts** · 11-08-2010 06:57 AM

Originally Posted by gearhead1186

i did the same. any plans on passing readiness or paying your way thru?

I guess i forgot about people keeping the stock tank. I didnt have to tie any of my stuff back together because I dont have anything there. Stock tank is gone. Fuel cell in the Trunk. But as far as emissions go, luckily we dont have any tests in SC.

**nthusiastt** · 11-16-2010 09:25 PM

Alright, I went out and took some pictures... Here's what I'm thinking for the tire tub section:

This motor I'm not sure if I can just remove?

Can I just cap the open section on the right off?

**1sadavant** · 11-16-2010 10:00 PM

Can't help you there, I just removed the canister. Where is all of that other junk hiding? If you are going to remove all of it, that may throw a CEL and you may have to get it tuned out... Any idea on the weight of all that stuff? I know the canister alone is around 8-10lbs.

Your T-fitting diagram is right on the mark though.

**nthusiastt** · 11-16-2010 10:22 PM

The pump thing is under the driver side rear quarter. The other T fitting and tank is under the passenger side fender. I traced the whole system to this garbled mess here:

The outlined section is "evap" related.

**J-b5** · 11-17-2010 04:25 AM

that line you have highlighted that runs down the the bottom middle of the picture is not evap related, its the pressure equalizing line that runs between each turbo inlet pipe. useless in my opinion but no need to eliminate that.

**nthusiastt** · 11-17-2010 07:18 AM

^^ Gotcha, I was looking at that and thinking I may have mistraced it. Thank you though for the info!

**1sadavant** · 11-17-2010 09:08 AM

Originally Posted by nthusiastt

Alright, I went out and took some pictures... Here's what I'm thinking for the tire tub section:

This motor I'm not sure if I can just remove?

Can I just cap the open section on the right off?

Where is this piece? Is it in the passenger side rear fender well? I am still getting resistance at the pump when filling. It's much better than before, but I feel that there maybe other components that are clogged. There was this yellow gelatinous stuff in the lines when I removed the canister, and can only imagine that this is clogging it.

**J-b5** · 11-17-2010 09:25 AM

thats the evap leak detection "pump"

you can diasemble them easily and clean the seals on them so they work properly again.

I did this on mine.

**nthusiastt** · 11-17-2010 09:27 AM

Originally Posted by 1sadavant

Where is this piece? Is it in the passenger side rear fender well? I am still getting resistance at the pump when filling. It's much better than before, but I feel that there maybe other components that are clogged. There was this yellow gelatinous stuff in the lines when I removed the canister, and can only imagine that this is clogging it.

This pump is stuffed up in the back section of the rear quarter panel.

Originally Posted by J-b5

thats the evap leak detection "pump"

you can diasemble them easily and clean the seals on them so they work properly again.

I did this on mine.

What's the benfit of that? Quicker pit stops at gas station fill-up?

**Scotty@Advanced** · 11-17-2010 09:32 AM

The only parts in the wheel well are the carbon canister, of which it can be removed, however removing the entire evap/vent system might not be a good idea.

Within the evap system and tank vent is what is called a rollover valves. Remove that and if your car ever goes wheels pointing towards sky, fuel will leak from the tank vent into places where you don't want fuel to be (in your back seat). A potentially bad situation. Also if improperly vented, you can damage the fuel tank (fuel pump will collapse the tank) or end up with critters and all sorts of other vermin in your fuel supply.

**J-b5** · 11-17-2010 11:10 AM

Originally Posted by nthusiastt

This pump is stuffed up in the back section of the rear quarter panel.

What's the benfit of that? Quicker pit stops at gas station fill-up?

In my case when i switched to VAST, they didnt have the code disabled so i started getting a CEL for issufient vaccum.. Esentially when the leak detection pump did its leak detection cycle, the solonoid switches on, and the valve is closed. A reed switch detects if vacuum is holding or not. If the seals on the unit are dirty, they dont stay airtight, and the vacuum charge does not keep it closed long enough to pass the test, thus a false conclusion of a vacuum leak.

Took me a few hours of research, then testing to find the culprit in the system. And by the looks of it, mine was changed by the original owner at some point. That little air filter is to prevent dust from getting into it when it vents vacuum. But it looks like it was just fine particle dust getting past the filter that caused the seals to stop working.

not surprising considering how much dust gets kicked up in the air directly behind the wheel. Not a very smart setup.

Anyways if you ever get that type of code its work checking out the operation of the leak detection pump.

Aside from the purge valve, its a fairly simple system on the mechanical side, just one or two check valves and some lines. Looks worse than it is really.

**nthusiastt** · 11-17-2010 12:09 PM

Originally Posted by Scotty@Advanced

The only parts in the wheel well are the carbon canister, of which it can be removed, however removing the entire evap/vent system might not be a good idea.

Not to be a stickler but the pump is in the rear wheel well.

Originally Posted by Scotty@Advanced

Within the evap system and tank vent is what is called a rollover valves. Remove that and if your car ever goes wheels pointing towards sky, fuel will leak from the tank vent into places where you don't want fuel to be (in your back seat). A potentially bad situation. Also if improperly vented, you can damage the fuel tank (fuel pump will collapse the tank) or end up with critters and all sorts of other vermin in your fuel supply.

Are the "rollover valves" in the plastic container under the wheel well or is that simply a storage canister?

**Scotty@Advanced** · 11-17-2010 12:52 PM

Originally Posted by nthusiastt

Not to be a stickler but the pump is in the rear wheel well.

Sorry i meant the "Spare Tire Well"

Are the "rollover valves" in the plastic container under the wheel well or is that simply a storage canister?

The carbon canister is in the Spare tire well. I believe it also has some one way valves in it, as I broke one open and had a peak inside. I'm not sure of their function however. IIRC the roll over valves are in the vent tubing.

**nthusiastt** · 11-17-2010 12:58 PM

Originally Posted by Scotty@Advanced

The carbon canister is in the Spare tire well. I believe it also has some one way valves in it, as I broke one open and had a peak inside. I'm not sure of their function however. IIRC the roll over valves are in the vent tubing.

What's your thoughts on the removal of that carbon canister in the spare tire well and the plastic canister in the fender well?

**Scotty@Advanced** · 11-17-2010 07:03 PM

Originally Posted by nthusiastt

What's your thoughts on the removal of that carbon canister in the spare tire well and the plastic canister in the fender well?

I'd do it but keep the gravity valve in case things go tits up.

**nthusiastt** · 11-17-2010 08:31 PM

Originally Posted by Scotty@Advanced

I'd do it but keep the gravity valve in case things go tits up.

Where is the gravity valve? btw thanks for all the help Scott!!!!

**nthusiastt** · 11-18-2010 03:18 PM

bump..

**Trigger Happy** · 05-26-2012 08:18 PM

I'm resurecting this thread from the dead because I have a question. Will simply eliminating the carbon canister cause a CEL? Also nthusiastt, what did you end up eliminating and did it throw a CEL/ kill you or your car?

**Trigger Happy** · 05-27-2012 05:17 PM

Bump

**domantas** · 06-03-2012 11:25 PM

guys, more of this please. Im getting ready to remove this stuff as well. I emailed JFonz to see if he can disable my cel if I get around doing this.

**haggard69er** · 07-26-2012 02:36 PM

Bump...

**papuc14369** · 07-26-2012 03:00 PM

I've actually looking to fix a evap leak too, does anyone have the ETKA or equivalent diagram of the evap system?

**jibberjive** · 07-26-2012 04:28 PM

Check out the 2.7t self study guide for a diagram.

**nthusiastt** · 07-26-2012 06:07 PM

I pulled everything out. Even the canister in the front fender. I'm running open atmosphere through filters on each hose, however this pretty ignorant of me since I haven't done the research into the reprecussions.

**haggard69er** · 07-26-2012 06:26 PM

**haggard69er** · 07-29-2012 11:43 AM

ok, so if i wanted to get rid of everything, how would i go about it?

**16g-95gsx** · 12-19-2012 08:05 PM

Just wanted to chime in as I was looking into factory schematics for the evap system while I had the engine out and could easily remove things.

The actual valve that vents the vapors into the engine had two outputs, one leading into the turbo inlets, the other into the manifold plenum. Both lines have check valves installed. The reason for Audi to do the system like this is so that if the throttle plate is open, the pressurized manifold plenum is blocked by the check valve and the vapors vent into the compressor inlet. If the throttle is shut, the largest vacuum is in the plenum and the vapors vent into it.

I'm going to ditch my entire system tomorrow and vent the rollover vent to the air. The codes will be flashed out of the ECU. I see this engine as having entirely too many complete hose systems and this is just one more potential failure down the road.

**haggard69er** · 12-19-2012 08:35 PM

Originally Posted by 16g-95gsx

Just wanted to chime in as I was looking into factory schematics for the evap system while I had the engine out and could easily remove things.

The actual valve that vents the vapors into the engine had two outputs, one leading into the turbo inlets, the other into the manifold plenum. Both lines have check valves installed. The reason for Audi to do the system like this is so that if the throttle plate is open, the pressurized manifold plenum is blocked by the check valve and the vapors vent into the compressor inlet. If the throttle is shut, the largest vacuum is in the plenum and the vapors vent into it.

I'm going to ditch my entire system tomorrow and vent the rollover vent to the air. The codes will be flashed out of the ECU. I see this engine as having entirely too many complete hose systems and this is just one more potential failure down the road.

Good info! I guess i Will update as well. I removed everything, but kept the n80 and leak detection pump plugged into the wiring harness. I bought resistors, but have not installed them yet. The resistors will emulate the n80 and leak detection pump being still plugged into the wiring harness. If there is another way to do this such as coding out, please let me know. Also, put a filter on the end of the hose that goes to the gravity valve. Btw, this sheds about 13lbs lol.