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2006 Subaru Outback 3.0R
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Discussion Starter #1
Hi,

I've recently started having gas smells, especially after filling up the car, and I got these codes: P0442, P0457. It's a 2006 Outback 3.0 with 200K.

The smell comes from the back wheel/gas cap area, but I haven't seen any leaks on the ground. I think the smell disappears as the tank empties. (I once just put 20$ of gas in a near empty tank and I didn't smell anything)

I started by buying a new gas cap since it was the cheapest thing I could do to try to fix it, but I still get the smell.

I've now removed the wheel and mud guard to have a look at the neck filler. It doesn't look that bad, but perhaps I have line connections that are not good anymore?

Here are the pictures I took... what should be my next move? Thanks!
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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16,119 Posts
I think the filler neck looks fine. What happen is you overfill it? It is possible one of the smaller vent tube nipples has rotted off.
 

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2017 2.5i Premium Lapis Blue
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4,197 Posts
I'm sure there will be others more knowledgeable about working on Subarus than I am but I will put my 2 cents in since I had this exact thing on a completely different vehicle. A couple of months ago I had a check engine light and several evap codes on my 2010 GMC Sierra. For a while I could reset the codes and everything was normal for a few days or more. Eventually the light would just come back on right away and I started smelling gas when walking up to the vehicle, especially right after filling the tank. After a couple of Google searches I also replaced the gas cap, also because it was the easiest and cheapest thing to try, and also because I was working every day and didn't have time to mess with it. The new gas cap made no difference and I just kept driving it, figuring it was just an emissions thing and probably just a vapor line leaking. Finally, after filling the tank I saw that bottom of the gas tank was wet with gas, which was running down from the top of the tank.

Even with an inspection camera I couldn't tell what was leaking but I at least knew where the problem was. I still kept driving it because I didn't want to have to deal with dropping a full 26-gallon gas tank. When I eventually had some time off I instead opted to remove the back bumper and slide the box back to get access instead of dropping the tank. It turned out to be the main fuel supply line on the fuel pump assembly that was leaking. In fact it was so rusted it broke off completely the first time I touched it. I was probably just one big bump in the road from being left stranded had the line broken off while I was driving. Ended up having to replace the whole fuel pump assembly because there wasn't any good way to fix just the line where it comes out of the top of the tank.

Anyway, may be completely unrelated to a similar problem on a Subaru, but thinking something might be "just an emissions problem" that doesn't need to be addressed immediately like I did could be something more critical. I was fortunate and might even be a little quicker to act if something similar happens in the future. Probably not, but I might be.:grin2:
I usually muddle through these things myself, but the best way to find a leak in the emissions system is to have someone do a smoke test. The leaks can be hard to find if they aren't obvious like mine turned out to be. The smoke test makes them easy to spot.
 

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2006 Subaru Outback 3.0R
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Discussion Starter #4
What do you mean by "over fill"? I stop filling when the pump stops automatically
 

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On the Super Mod Squad
2002 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
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26,193 Posts
forced air smoke tester maybe necessary to find the leak.

I think your pipes look better then mine, I have bought a new inlet hose for my H6 car recently cost $90 US for it.
I had a p0442 (tiny leak), but the thing was a lot more rusted than yours, and I am trying to fix all the rust on the car there at the rear quarter. so the old one had to go anyway. that section is apart now, ....have not installed the new one yet.

____

on my H4 sedan there is more rust then the H6 car, been clearing codes for a p0456,
and found a open cirucuit with a wire connector apart back there with the EVAP system. ...

neither of my cars ever smelled of gasoline though.


and I would suggest looking at those sensors and seeing if there is a wire problem with them while you are looking for your leak.
 

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2006 Subaru Outback 3.0R
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Discussion Starter #6
Smoke tester does seem like a logical next step. For now, I added a clamp where the filler neck meets the hose since the original clamp is super rusted (pic) so maybe it's not air tight anymore. I cleared the codes and left the mud guard off so I can take a peak next time I smell gas.

One thing I'm wondering is what would make it smell only when the tank is fuller?
 

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2001 VDC/SC One of a Kind
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You don't have to see a leak for there to be one. Fumes, gaseous state, can escape without leaving residue. That's the purpose of the EVAP system, to withdraw the fumes to the engine to be mixed with intake air instead of allowing them to vent at the gas cap like the old cars.

Did you use a Subaru gas cap? Most aftermarket suck and don't seal.

Dito getting the system smoked. You could have a tiny crack in a hose, or pipe, and you won't see it until the smoke escapes the system.

At the rear of the car is the filler tube, vent pipe, charcoal canister and all the related pipe and hoses that connect it all.
 

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06 OBW 2.5, 05 Forester, had 03 H6 OBW
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The part of the fuel shut-off valve on the neck that you can see looks good... if you can't get a mirror all the way around it, it might have a rust hole.

I took an old gas cap apart, put a piece of plastic hose through it, put it on in place of the gas cap, got a good mouthfull of cigar smoke away from the car then blew smoke into the hose- found leaks right quick but not the method for everyone.
 

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2006 Subaru Outback 3.0R
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Discussion Starter #9
Wow... So I basically HAVE to enjoy a cigar to troubleshoot this? ?

Do you a link that shows this technic in a bit more detail?
 

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On the Super Mod Squad
2002 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
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Wow... So I basically HAVE to enjoy a cigar to troubleshoot this? ?

Do you a link that shows this technic in a bit more detail?
in previous discussions of smoke testers that I have read.

DIY cigar/cigarette is not going to do it.

vs. some $$$ smoke machine that a big fancy garage would have or a parts store would loan,

but still be costly for a small mechanic to buy.
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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What do you mean by "over fill"? I stop filling when the pump stops automatically
I meant ... keep going. If you look at how the tank is designed, there is a vent bubble at the top. So, when it is full, there is still an air pocket. All of these nipples and filler neck are in this air pocket. If you overfill it and gas starts running out, one of 5 ( I think) nipples is rotted or hoses cracked.

That's just the quick and easy redneck way to see if the tank has a breach.
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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16,119 Posts
DIY cigar/cigarette is not going to do it.
It depends what you are trying to do. Isn't smoking around fuel vapors a bad thing? I suppose if the diagnosis goes horribly wrong and you decide to pull a Walter White and torch your Challenger


Then a ciggy just might do it.
 

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2006 Subaru Outback 3.0R
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Discussion Starter #13
What do you mean by "over fill"? I stop filling when the pump stops automatically
I meant ... keep going. If you look at how the tank is designed, there is a vent bubble at the top. So, when it is full, there is still an air pocket. All of these nipples and filler neck are in this air pocket. If you overfill it and gas starts running out, one of 5 ( I think) nipples is rotted or hoses cracked.

That's just the quick and easy redneck way to see if the tank has a breach.
Ah I get it... By overfilling I should see liquid gas leaking where gas vapor is currently escaping?
 

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Premium Member
2001 VDC/SC One of a Kind
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The part of the fuel shut-off valve on the neck that you can see looks good... if you can't get a mirror all the way around it, it might have a rust hole.

I took an old gas cap apart, put a piece of plastic hose through it, put it on in place of the gas cap, got a good mouthfull of cigar smoke away from the car then blew smoke into the hose- found leaks right quick but not the method for everyone.
Wow... So I basically HAVE to enjoy a cigar to troubleshoot this? ?

Do you a link that shows this technic in a bit more detail?
This is getting comedic. :grin2:

You don't have to smoke it. You could find a smoker on your block and ask them to blow into your filler pipe.
 

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Discussion Starter #15
So I put a rubber glove around the gas inlet, held with an elastic, with a straw poking out of a finger, and lit up an old Montecristo. Besides just a little bit of smoke passing through the rubber band, I didn't spot any smoke coming out behind the wheel.
 

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2005 Subaru Outback XT MT / 2012 Subaru Outback 2.5i Premium
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The top of the fuel pump is a cheaply made thin piece of plastic that cracks. The crack is not easy to see. When I removed the bolts, it was more obvious as discolored streaks. I suppose you might be able to see it better if you poured a dark staining liquid over the top. Perhaps wine or cranberry juice or something. Fuel vapor can easily leak through tiny cracks, and then liquefy the moment it hits our low pressure atmosphere, so the pump top should smell of fuel if it's leaking. Access to the pump is under the passenger side rear seat IIRC. Fortunately, it very easy to change the pump, unfortunately, it's flipping expensive for the part, especially on a CA emissions vehicle.
 

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Discussion Starter #19
I did remove the back seat to smell over pump area (without removing the cover plate) and I didn't see or smell anything. Also, when it does smell, it's more from the back passenger wheel area. I cleared the codes the other day and they haven't came back yet, but did very little mileage so far.

Does anyone know the procedure of systematically testing various inlets to check for air leaks with an air pressure pump and gage?
 

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2001 VDC/SC One of a Kind
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First off, my Outback is over 208K miles and still has the original fuel pump assembly (fuel pump replaced with a DW300) and its not cracked. I have worked on 100s of Subarus over the years and have never seen one cracked. If you have a cracked assembly, its probably because someone tried to tighten it down without insuring the assembly was seated on the tank and overtightened it while it was cocked.

Here's and idea for you since you brought up pump and gauge: I've never tried this, but just thought of it. The EVAP system is designed to hold pressure and vacuum. So you can either get a hand vacuum pump and utilize the EVAP hose at the engine to pull a vacuum on the system, not the intake, and watch the gauge for a rise in pressure, don't pull more than 5 inHg, or, you can use a bicycle pump or other pump and pump air in to the system, don't pump more than 3 psi, and listen for the leak or watch a gauge for a drop.

If you want to get crafty, and this comes back to smoking, you could jig up a smoke machine of sorts by getting yourself a large balloon, taking in a large, smoky puff, and fill the balloon with smoke. Once the balloon is nice and full of smoke, put the balloon on the EVAP hose at the engine and let the pressure in the balloon push the smoke in to the system. (You use the EVAP hose at the engine because it is the end of the line for the flow of fumes and this pushes the smoke reward to the tank and canister.) Leave the balloon on the hose as a seal and look for the smoke to escape. Again, you can have a leak visible with as little as 3 psi pressure, so if your tank is above 3/4, it won't take much to put the pressure on the system.
 
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