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I've been dealing with this code for the past couple months. It's on a 97 Legacy L AWD Wagon 136K. Light first came on around 134K. The light only comes on at freeway speeds with under 85% fuel left

 

I've already tried switching gas caps with 2 different friends. CEL came back on for me both times, and never went on for them.

 

There is no rust on the filler pipe (Car's been in california since 2000)

 

I just tried a homemade smoke machine to try to find a leak, but couldn't find anything, however, verified pipes are not clogged.

 

I've bench tested all 3 (purge, vent, pressure control) related solenoids, by applying 12VDC from a power supply. All solenoids clicked, however if I blew really hard on the pressure control solenoid, it would still allow some air through. However, I think (but am not certain) that is the expected behavior.

 

I've used the test connector under the dash to verify the wiring to the 3 solenoids is functioning.

 

Are there any other things I can check? Is it possible the vapor canister is clogged? Is there a way to check that?

Edited by jamesm113
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I think I found the leak, almost by accident.

 

I was originally on planning on taking the car into get smoke tested today, but since I had the canister out, last night I figured I'd give things one last try when I was putting it back in.

 

I had a friend attempting to pull a vacuum from the purge line in the front of the car, while I laid underneath the canister, plugging the vent line with my thumb. Since this took a while my eyes started wandering and a cracked hose miraculously caught my attention.

 

The hose was the air vent hose, in between the gas tank and wheel well. It's pretty far in, but of course, I now feel like an idiot for not seeing it earlier. :banghead:

 

The side closest to the wheel well had some cracks around the hose clamp, with one extending about 1/4" towards the middle of the pipe. The other end, which attaches to the gas cap (you can spot it through one of the holes in the rear crossmember) had about a 1/2" crack.

 

Anyone know if I can lower the rear crossmember a couple inches without removing anything but the 4 bolts that attach it to the frame? I just need a couple inches to work.

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Thanks Fairfax, those couple inches was enough to get the hose out. Gas cap is fine though.

 

Both ends of the hose were cracked. Since it was a 5/8" hose made by Gates, I don't think it was factory installed, and I bet it being the wrong hose and size had something to do with the premature failure.

 

EDIT Hose is Subaru Part Number 42162AC030

post-35908-136027653895_thumb.jpg

Edited by jamesm113
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I've been living with a P0440 code for a while ('97 Impreza) and now it's gotten significant since I have to re-new my registration in March and this year requires an emissions test via the OBDII reading.

 

I had picked up all the obvious pieces from another Impreza wagon and had them installed recently (my son works at an independent shop). It looked hopeful when he pulled the charcoal canister and found charcoal coming out one of the fittings if you turned it upside down and shook it. After cleaning out the hoses leading to the canister all the parts were installed, the CEL was re-set and I starting driving it to rack up the 200 miles required to pass the OBDII test.

 

In my reading up on the P0440 code, I had found it would trigger when a full tank of gas got down to 9/16th full if there was a leak in the system. Numerous tankfulls confirmed that for me. Last evening I got to 150 miles since the re-set and I was getting close to the half-way mark on the fuel gauge. No CEL yet, but I topped up the gas tank to be sure it wouldn't trigger on this test cycle. Got home with 202 miles since the last code reset. I'll be going to emissions testing as soon as they are open this morning. Wish me luck.

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Good luck, Ed. Sounds like you're gonna' be okay. Let us know.
Thanks for the good wishes. Passed the OBDII check. I had logged 223 miles since we re-set the CEL after installing the used emissions parts. I chickened out last night before I ran the tank down to half, so I had topped it up to be sure it wouldn't fire off a CEL in case the used parts didn't clear the problem. I'll report when this tankful is replaced to see if the CEL is really cleared.
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Well, today as I was running up the rest of the miles on this tankful, the check engine light came on! Pesky P0440 error. Looks like we'll have to drop the rear cross-member and inspect that hose.

 

I didn't have to have to drop the cross member to spot my leak. Follow the air ventilator hose from the filler neck. On the other side (interior side) of the wheel well is the first spot it connects. Mine was cracked there. Then, there are a couple holes in the middle of the cross member. You can spot the other end of the hose through those. It's behind the filler neck tubing. Mine was cracked there as well.

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Also have you checked the hoses in these locations:

 

1. Between the firewall and the intake manifold (it's one of three hoses), by the fuel filter

2. Between the intake manifold and the purge solenoid

3. Between the purge solenoid and the throttle body

4. Underneath the car, near the rear driverside wheel, on the side of the fuel tank, there are 3 hoses about a foot in length. One of those is the EVAP purge line.

5. Between the EVAP canister and the roll over valve, pressure control solenoid.

6. Between the vent solenoid and EVAP canister

 

If you have an assistant and a vacuum pump, you can test segments of the system one at a time:

 

1. Pull the line from purge solenoid and attach the vacuum pump. Have an assistant pull the purge line from the EVAP canister and plug it with their thumb. A vacuum should register immediately. If not, there is an issue with the purge line

 

2. Reattach the purge line. Have assistant disconnect charge and vent lines and plug holes with fingers. Vacuum should register immediately.

 

3. Detach charge line and attach vacuum pump. You should be able to build up a vacuum of about 1-3psi in a couple minutes and it should hold.

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