99 Century 440 Code, NOT Gas cap

[BuickBuff]

Hello all,

So I've used many forums like this one for advice as I'm a do it yourself'er when it comes to fixing cars, but a teacher by trade. I'm fairly good when it comes to this kind of stuff (with my other 2 vehicles I've owned, an '88 Bronco II, and a 2001 Explorer I've had LOTS of practice!) but it seems that I'm dealing with something that I have yet to encounter

I have a 1999 Century Custom that I bought relatively cheap about a year ago (for better gas mileage) and this past week it finally hit 100,000 miles. About I would say 5 months or so ago I got the 440 EVAP code. Knowing the history of this code the first thing I did was go out and replace the fuel cap (the previous owner had installed a locking cap, so I figured this was the problem to begin with). Well no such luck in this case, it's still on.

The other issue I have outside of the light being on is every time I go to fill up I have to watch the gallons going in because if I leave it running until it shuts itself off, gas will shoot back out of the hole and get all over. Also when filling at "full service" stations (especially on the NJTP for some reason), sometimes it will not fill up even on empty (it will fill for a few seconds, shut off and spit out at the not so happy attendant).

I'm assuming its one of the lines or valves or even the canister, which would require a trip to the shop as I don't have a smoke machine, but is there anything else anyone else could think of that I'm missing?

Thanks all for the advice and thank you for hosting a great website!

Buff

 

[Metrix]

It's most likely the EVAP Vent Valve (solenoid) aka Canister Purge Valve Solenoid. It opens and closes the vent from the tank to the vapor canister. The piston in the valve eventually rusts and the valve will lock into position. In your case it's closed but leaking since it's not venting the tank when you fill up but throwing a P0440 (large leak) when the EVAP test procedure is run.

The solenoid is located behind the drivers side rear wheel well on a clip attached to the top of the vapor canister. Unbolt the vapor canister to get access to it.

There is a filter attached to the solenoid, unlatch it and turn 45 degrees to remove it.





This is the piston in the normal (open) position. You can test it by applying 12 volts to the the two terminals, polarity doesn't matter. If yours is locked in the extended position (closed) then it needs to be replaced.
It is possible to oil the piston and carefully pry the piston back into position but it will only last until the piston shaft starts rusting again. A new one costs around $39.
Some auto parts stores list 2 different parts as Canister Purge Valves, make sure you get the correct one.

 

[BuickBuff]

Thanks so much! This makes a LOT of sense as the car was previously owned in a lake effect area of ohio and has a lot of "Northern Exposure" rust underneath. In fact it's so rusty that I'm afraid I'm going to break the bracket on the canister so I'm going to wait till I can get to my junkyard and find a replacement bracket (and I'll grab one of those solenoids while i'm at it) in case it breaks while removing it.

Again you guys

Buff

 

[moreira72]

My 99 had the same code, and i also bought a new gas cap. But the code was still there. Took it to a shop, and they smoked it and found one of the vent tubes that goes from the filler neck to the gas tank had a pin hole from rust. The guy cut away the bad section of pipe and repaired it with a rubber hose and two clamps. Its been like that for six months and no more code 440

 

[BuickBuff]

Just as an update I replaced the solenoid (and the attached filter, it was just easier) with one out of a 97 which had a smaller tube and hose, but with a new hose clamp eventually did fit on mine. Also replaced the vapor canister bracket as mine had some serious rusting issues.

Turned off the light and have driven it for about 3 hours (1 1/2 each way) and so far so good! 😀

 

[BuickBuff]

Alright friends, I hate to bring this back up again but about 2 days after I posted that things were looking fixed, the code came back on again. I finally went and tested the old solenoid and it did fire correctly, so apparently that was not the problem (I was afraid that maybe the one I got out of the junkyard was also bad). I also had a mechanic check the fuel lines and they are all good. My next guess is the canister? Any thoughts would definitely be appreciated.
Thanks!

 

[Metrix]

When the PCM does the EVAP test it closes the vent solenoid at the canister and introduces a small vacuum into the entire EVAP system through the canister purge valve (located behind the coil pack). The fuel tank pressure sensor monitors the vacuum. If the PCM sees no change in pressure/vacuum it assumes a large leak and you get the P0440.
Normally a smoke test is used to find leaks in EVAP systems. Check all your hoses for leaks. Was the seal in the vent solenoid ok?
Here is a full list.

Disconnected or faulty fuel tank pressure sensor.
Leaking fuel cap seal.
Disconnected, damaged, or blocked EVAP purge line.
Disconnected or damaged vent hose.
Disconnected or faulty EVAP canister purge valve solenoid.
Disconnected or faulty EVAP vent valve solenoid.
Open ignition feed circuit to the EVAP vent or purge valve solenoid.
Damaged EVAP canister.
Leaking fuel sender assembly O-ring.
Leaking fuel tank or filler neck.