1999 Impreza Wagon CEL PO440 Evap code

[paulbellefeuille]

Okay here's one that probably comes up alot but since I don't get a chance to come by here very often I thought I'd ask.
My wife's '99 Impreza with 85,000 on it just had the CEL come on for code PO440. Evaporation system.
I changed the gas cap and the light remains on.
I don't hear any vacuum leaks when the hood is up.
So I put the question out to you all.
What could the problem be?

[tbolt1003]

When you say that you changed the gas cap and the light stays on, did you clear the code and the light reappeared or have you not cleared the code yet? The light will stay on until you clear it.

[Fairtax4me]

P0440 is one of the early codes and its really vague, so finding the cause can be tricky.

 

A few things to check.

These are famous for the fuel filler pipe in the right rear wheel well rusting out and developing pinhole leaks. Remove the plastic cover over the filler and check it for wetness/fuel. Replacements are about $120 new. Used can sometimes be a good option if you can find one that was recently replaced.

 

Depending on model year you could have the charcoal canister under the hood, or at the back of the car behind the right rear wheel. If its under the hood make sure the hoses are connected properly. One of those hoses leads to the evap system purge solenoid which is under the intake manifold on the passenger side. With some poking around and a flashlight you can figure out which. Remove that one from the canister and try to blow through it. No air should pass. If you have the canister at the back of the car there is a small hose that connects to the intake manifold on top of the throttle body that leads to the purge solenoid. Use that hose for the same test. Then find the green test mode plugs under the dash near the steering column, connect them and turn the key ON. The solenoid should click in roughly 1/2 second intervals. Blow into the hose again and air should flow then stop in conjunction with the clicking of the solenoid.

If the solenoid doesn't click its dead.

If no air flows at all the solenoid is clogged.

If air flows all the time the solenoid is stuck open.

 

I've had mice/squirrels chew the evap lines next to the tank at the back and had to replace those (which is not easy or fun). Check over all of the hoses near the tank and the canister if the canister is rear-mounted.