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P0440: Evaporative Emission Control System Malfunction.

Not quite sure where to start with this one (I do know the EVAP system). I have as of 3 months ago replaced all the rubber lines for the EVAP system.
I did not see any that have become unplugged or loose.

Which of the 3 should I look into as the culprit for this code: vent solenoid, charcoal canister, purge solenoid, or even any of these?

I'm up for suggestions, thanks guys.

I'm interested in the responses for this one also.
I have the same code show up about every other fill-up...MIL light somes on at about 1/2 to 1/4 tank and when I remove the gas cap to fill up, TONS of air somes out. I reset the light, then 2 tank fills later, do it all over again.
Been doing this for about 6 months now.

Slight update, after resetting the aforementioned code it has not reappeared.

Was this just a fluke?

Just seems weird that the whole EVAP system would just malfunction.

dangrus4060 wrote:I'm interested in the responses for this one also.
I have the same code show up about every other fill-up...MIL light somes on at about 1/2 to 1/4 tank and when I remove the gas cap to fill up, TONS of air somes out. I reset the light, then 2 tank fills later, do it all over again.
Been doing this for about 6 months now.

Are you sure its not air going in?

You could have a vacuum drawn on your gas tank.

Any metallic thumping noise from gas tank?

Possibly your fuel tank pressure sensor is malfunctioning.

THE FUEL TANK PRESSURE SENSORS ARE UNUSUALLY SUSCEPTIBLE TO MALFUNCTIONS. IF THE SENSOR MALFUNCTIONS, EXCESSIVE VACUUM CAN BE APPLIED DURING SELF-DIAGNOSTIC TESTING.

Nope, definitely air PRESSURE...I can feel the air rushing past my hand as I undo the cap along with an immediate strong smell of gas vapors...and sometimes droplets of gas accompany it...wouldn't be doing that if it was vacuum...and I think if it was THAT MUCH vacuum in the tank, it would collapse.

Bing wrote:Slight update, after resetting the aforementioned code it has not reappeared.

Was this just a fluke?

Just seems weird that the whole EVAP system would just malfunction.

How long since you cleared the code? My experience with this tells me it will come back. I've been dealing with this same issue for some time now. Just haven't had time to investigate.

dangrus4060 wrote:Nope, definitely air PRESSURE...I can feel the air rushing past my hand as I undo the cap along with an immediate strong smell of gas vapors...and sometimes droplets of gas accompany it...wouldn't be doing that if it was vacuum...and I think if it was THAT MUCH vacuum in the tank, it would collapse.

It appears your Evap system is not purging the fuel vapor collected from the gas tank. You need to check the vent line from the gas tank to the charcoal canister for free flow. Plus check that the purge and vent solenoid/valves are working properly. When you remove the gas cap, fuel vapor is escaping that is supposed to be stored and then burned in the engine.

About a week now, so far so good.

My 97 SSEi is doing the same thing with the air pressure escaping when opening the fuel cap.

Does anyone have the schematics for the Evap system or where I should look for the problems.

Bing wrote:P0440: Evaporative Emission Control System Malfunction.

Not quite sure where to start with this one (I do know the EVAP system). I have as of 3 months ago replaced all the rubber lines for the EVAP system.
I did not see any that have become unplugged or loose.

Which of the 3 should I look into as the culprit for this code: vent solenoid, charcoal canister, purge solenoid, or even any of these?

I'm up for suggestions, thanks guys.

I would go for the purge solenoid first. Haven't had mine go bad, but the Crown Vic Police Interceptors I work on every day have had the same symptoms/codes, and the purge solenoid is the problem 99% of the time. Not the same car, but it's all OBD2. Very similar systems.

There are no codes being generated with my issue- Just huge amounts of pressure when opening the cap.

I have started leaving the cap slightly loose as in Fla it gets hot out- Don't need any KABOOMS

The most common resolution I see for people with this code is the gas cap. The rubber seals on the cap get dried out and cause the tank to lose the seal. This doesnt sound like your problem if you hear that much vacuum when you open your cap. I agree with checking the purge solenoid.

The reason why this code comes back after a while is because it is an intermittent test. The pcm will do a pressure check on the system every 1k miles or w/e interval is set. So when you clear the code w/o fixing it it will take some time before seeing it again.

Mastersj, I dont know how you dont trip a code if you leave the cap loose. Have you noticed your mileage decrease since doing this? (as you are letting you gas evaporate away)

Well, my issue hasn't shown it's ugly head as of yet (4 months now). As far as I know I still have the original gas cap on the car, so I'll see if it returns.

Mastersj, I think that your EVAP system is plugged somewhere in the lines, or the charcoal canister.

Just my 2 cents.

Have been dealing with this one for months as well. Used to come on every time I'd get below 1/4 tank or so in the summer. Temperature changed, and it was far less common, and was gone for easily 3 months before it popped back last week along with a ineffiecent cat code. Strange.

Does anyone have any info on my issue?