Intermittent fuel smell in cabin. No MIL.

[GTA]

I've searched the forums and can't seem to find anything similar to my situation.

Just some background that I've recently changed out my clutch and power steering rack and an oil change. I can't see any correlation but I thought I'd disclose that to add some insight.

I've been getting a strong fuel smell in the cabin lately and seems to be getting worse to the point that I have to crack open the windows so it doesn't burn my eyes (I have senstive eyes in my old age). It started abruptly - one day it was fine and the next I smelled it when I left the car. And now it's crept into the cabin.

I haven't scanned the car for DTC's but there's no MIL's lit and the car drives normally with no hesitation nor starting issues. I did notice that it seems to have less torque around 2K rpm than it used to, though it could be in my head and the response of the new clutch. I dunno.

I've only attempted to look and sniff for the leak with the engine shut off but can't nail it down to anywhere since gas evaporates so quickly so there's no visible signs of a leak.

All my injectors are stock, as far as I know, and it seems to be coming from the engine bay.

I've never really had to troubleshoot fuel systems before so I have no idea what to check for other than visible leaks and smells.

[Charles.waite]

The EVAP and fuel lines run right by the cabin filter. Maybe they're leaking and getting sucked in to the HVAC system and blowing into the cabin?

[GTA]

Good to know. I'll have a look at that this weekend in a nice warm shop. Thanks Charles.

[old guy]

I had a similar situation a few months ago. I looked everywhere and finally found the source. The Schrader valve on the back of the fuel rail was leaking. I tightened up the valve and problem solved.

[GTA]

The Schrader valve on the back of the fuel rail was leaking. I tightened up the valve and problem solved.

It can't be that simple, right Fletcher? Any reasons you can think of why your Schrader valve need to be tightened?

[old guy]

No, I can’t. I have never removed it but I have depressed it numerous times over the years to dump the fuel pressure. Once I tightened it everything was cured. I guess vibration over 240K miles must have loosened it a little.

[DownhillA4]

Possibly a fuel line on the fuel filter backed off and is leaking. Had this happen on a roadtrip a few weeks ago. Opened the car door and it wreaked of fuel smell. Walked around car and a puddle was under the fuel filter area, a line had come loose.

[GTA]

I went down to the shop and scanned my car with VCDS - no codes pertaining to my fuel smell issue and still no MIL.

I sniffed around and the smell is definitely coming from the top fuel rail somewhere but I couldn't determine any leaks. Just for sh!ts, I replaced the Schrader valve and it still smells. I knew it wouldn't be that easy to find .

I sprayed some kids bubble making fluid mixed with water on the fuel rail and around the injectors but didn't find any noticeable bubbling. This may be the wrong procedure for finding a fuel leak but that's all I've come up with.

Yeah, I'm a noob at this as mentioned before. Now that I think of it, I should have injected pressurized air into the Schrader valve - I believe that's what it's for, right?

Anyone replaced the injectors seals on the AMB 1.8T that can give me a couple of pointers? I know Old Guy has done it with aftermarket O-rings but I can't find the ones he suggested in Canada.

[rocket1420]

Don't inject pressurized air into the Schrader valve! I'm not sure what would happen, but maybe blow out the injectors, build up too much pressure against the check valve.

That valve is to relieve fuel pressure in the system in order to work on associated components. It is also where you can hook up a fuel pressure gauge.

[MikTip]

Under the rear seat..., drivers side...

My fuel level sensor plastic top cracked. was leaking fuel.

http://www.audizine.com/forum/showth...er-Replacement

Smelled in cabin...replaced, no more gas smell in cabin

[19jdog]

Under the rear seat..., drivers side...

My fuel level sensor plastic top cracked. was leaking fuel.

http://www.audizine.com/forum/showth...er-Replacement

Smelled in cabin...replaced, no more gas smell in cabin

+2

My work around so far is to put 10 or 11 gallons in instead of completely filling all the way up. I will be replacing my sensor soon though.

[seanf86]

I had this problem on my B5 A4 is the fuel fitting on the rail would leak on a cold start once the engine warmed up it would dry up and the smell would be gone. My B5 S4 just started leaking at either the upper o rings at the rail or its coming out at the injector bodies. Just 2 more places for you to check, as soon as you start the car when its cold, pop the hood open and sniff around.

[GTA]

I smell the raw fuel from startup of the cold engine and when not moving or moving slowly in traffic. No smells when going faster or on the freeways so it's not coming from the fuel sending /pump areas under the rear seats. I also smell it when shutting down and getting out of the car, so a hot engine doesn't make it go away, unfortunately.

Like I've mentioned, it's definitely coming from under the hood and near the fuel rail area and I highly suspect the fuel rail, injectors, etc. My problem is nailing it down to an injector or the somewhere along the fuel rail.

Gotta hunt down the procedure to replace O-rings, injectors, etc. It doesn't look to involved but it'll be new to me as I've never had to replace these components.

[caluma4x4]

I had this recently, there is a rubber t piece that connects the crank case breather, pcv valve and cam cover breather, it was split leaving the pcv valve dangling. The smell was only apparent when stationary and mpg dropped to about 32 mpg (UK)
I hope this is your problem, please keep us posted of what you find, it could be any of the pcv pipe work so check carefully.


Sent from my iPhone using Tapatalk

[GTA]

Yeah. I have to look more carefully and precisely to nail this down. It's really getting irritating and potentially dangerous since it's cold out and I need the windows closed.

Why couldn't this happen when it was warmer? I'll have to check it more carefully next weekend at the garage and hopefully find the culprit. I'll keep this thread alive until I solve it.

Thanks everyone!

[Charles.waite]

If an injector is leaking you’d see varnish and scuzz (technical term) all around it. My vote is a torn or packed out o-ring.

[GTA]

If an injector is leaking you’d see varnish and scuzz (technical term) all around it. My vote is a torn or packed out o-ring.

I've removed the fuel rail and injectors to inspect and I noticed no 'scuzz' marks on any of the four injectors - they're actually very clean for being under there for all these years, and there doesn't seem to be any visible cracks on any of the injectors either.

Here's what I've done this past weekend:

- Replaced upper and lower injector O-ring seals with the Standard Motor Products SK1 O-rings -> http://www.rockauto.com/en/moreinfo....=47159&jsn=278
I carefully took a razor blade to slice the old ones and used the cone tool to install the new ones. Using this method, I didn't break the lower washer-like seal retainer.

- I didn't want to remove all the vacuum lines and plumbing so I partially removed the intake manifold (IM) enough to change out the IM gasket, slip a rag under the runner ports to contain any broken injector cup fragments and replaced the four injector cups (non-technical term). I didn't have any luck removing them in one piece even though I took a heat gun to each in an attempt to soften them up. So I had to chisel each one out with a small flathead screwdriver and the smallest hammer I can find and cleaning out the glue residue on the threads. This was tedious but was mostly removed in large pieces.

In the process, one of my check valves snapped like twig. I found a smaller check valve and rigged it in there temporarily. These are costly from Audi so I'm going to order a few of these for a couple of bucks each: http://www.rockauto.com/en/moreinfo....411232&jsn=397

I used plumbing Teflon tape for the injector cup threads. I've found that five wraps around was the right amount. Four didn't seem enough and six seemed too tight.



The car started and ran horribly after all of this. Scanning it revealed mis-fires and throttle positioning codes. I attributed the mis-fires to the fact I cleaned out the MAF sensor and throttle body as well. Doing a VCDS throttle body adaptation did the trick and all is good.

I had this recently, there is a rubber t piece that connects the crank case breather, pcv valve and cam cover breather, it was split leaving the pcv valve dangling. The smell was only apparent when stationary and mpg dropped to about 32 mpg (UK) I hope this is your problem, please keep us posted of what you find, it could be any of the pcv pipe work so check carefully.

Since doing all this didn't solve my problem, I will dig deeper into the PVC and EVAP systems since that's what's remaining for raw fuel under the hood. And it's definitely coming from under there.

Sorry about my ignorance about the PVC system on turbo vehicles, but does any know if a boost leak test would be able to help find the fuel smell from under the hood?

[kjmiles]

+2 on the PCV system. I had that smell too for quite awhile. I brought it to the and he ran tests on the PCV system and reported no problems. I continued to complain about it after I replaced the cabin filter, but he could still find no problems. Finally I took it to this other guy and asked him to check the PCV system and he said that there are several areas of the PCV that can fail, especially one down on the right side of the block that's hard to reach/get to. In the end he replaced several check valves and hoses and I haven't had the smell since. Glad I can actually give back for once!
KJ

[5ktq]

I think if you've got a big enough fuel stink that you have to open the windows there's gotta be a leak off the rail / assoc hoses.

pcv stinks a bit but not that bad

[GTA]

+2 on the PCV system.

Yeah. I have to find the time to inspect everything closely and also to replace a few of the check valves. Also the EVAP.

I think if you've got a big enough fuel stink that you have to open the windows there's gotta be a leak off the rail / assoc hoses.

pcv stinks a bit but not that bad

The raw fuel stink is not as bad as it was but still noticeable in the cabin and more pronounced under the hood. There's just a faint smell now with the windows closed.

I'll provide updates as I progress and hopefully find the cause(s).

Thanks for everyone's input.

[GTA]

I had some time today and I've found the source of my raw fuel smell. It's the 'L' shaped crankcase breather tube (#06A103213F) : https://www.ecstuning.com/b-genuine-...be/06a103213f/

It's made plastic and became brittle with age. I'm sure I broke it when I replaced my clutch a few months ago. There's a lot of dried up gunk on the inside walls of this tube but I suspect this is normal for the age and mileage, though it's not nearly enough to clog this large-ish diameter tube.

I rigged it back in with some Kleen-Flo black gasket maker and a short length of rubber hose until I get a replacement. Good thing it's a common and inexpensive part and can be found anywhere, even on Amazon. I'll order mine from Rockauto since I need to get something else from there.

It looks to be a PITA to replace because of where it's located. So much plumbing.

[EuroxS4]

I had the fuel supply line going to the rail fail on me.I noticed a extended crank and smell.Car drove fine.The next morning when cranking the fuel line failed,had to replaced supply line at rail.

[GTA]

Finally replaced the breather tube yesterday. I couldn't justify buying a name brand for what is essentially a plastic tube so I bought an eBay one and popped it in. I did have to remove some plastic burrs from the inside of the tube though. I didn't remove the intake manifold and the job wasn't too bad. Worst part was removing the OE clamps. in a tight space without breaking anything else.

Problem solved and I can finally clean that part of the engine without fear of letting water in.