128i Evap Emissions System P0440 50k miles

[krando67]

So ever since I replaced my fuel pump, I've been getting intermittent P0440 codes. So far I've replaced the gas cap(brand new from stealership), fuel pump, fuel pump seal, DMTL pump and the purge solenoid(breather valve). Replaced the breather valve because I was getting P0440 and P0442 accompanied by running lean codes. I'm still left with the P0440 code that comes and goes whenever it pleases. I had to get the charcoal canister out to replace the DMTL, I didn't see any gas coming out of it or anything(not exactly sure how the charcoal canister works). But that's what I'm thinking of replacing next, mostly because that's pretty much the only thing left in the system that I haven't replaced yet.

I've noticed that the SES light comes on when the engine is hot and I'm in stop and go traffic. If I drive on the highway for 3 hours, it won't come on. But if I've been driving >30 minutes and I come to a stop light, that's generally when it'll come on.

I should also add that it doesn't smell like gas anywhere in or around the car at any time.

Any input would be appreciated.

[andrey_gta]

Inst this emissions system waranteed for some large milege? I recall TheStIG had a thread about this.

Also,
My car too has developed a fuel pump hairline crack/leak on a full tank... and its a n52. I too have replaced the pump caps & seals( the caps were so rusted), but now realize i need at least one fuel pump...

If it helps, I do not get any engine codes.

[JimD]

krando,

I think that is the code I have had for months. I do not worry about it but it is a bit annoying. I think my issue is the vacumn pump. I used to hear it and don't anymore. where is the charcoal cannister? The pump is in the same area. The way this system works is there is a pump to pull a vacum on the fill side of the tank and route the vapors to the charcoal cannister where they are absorbed. The whole purpose is to avoid gas vapor getting out. I would get a smoke pen and trace the system or have somebody do it. You may have a leak somewhere and the pen will tell you where. The light comes on when the sensor says the vacuum is not enough. Charcoal cannister should not matter.

Jim

[krando67]

Hey Jim,

The pump and the charcoal canister are both located on the passenger(right) side under the rear bumper. Thanks for the info on how the pump works. The pump is bolted onto the canister so it creates the vacuum through the canister. I really don't want to trace a leak anywhere because that sounds painful but I guess I'll have to. Do you have an idea as to how this makes the light go away when I have under 1/4 tank of gas?

[3002 tii]

Did you remove your charcoal filter from your intake box? If so try putting it back in else might be your fuel ventilation valve

[krando67]

3002 tii,

it's not the vent valve as I've replaced that already due to a P0442 code that popped up. Replacing that fixed P0442 but P0440 still remains. I have not removed a charcoal filter from the intake box, didn't know there was one. I was talking about the charcoal canister which is just inside the rear bumper.

[3002 tii]

Easiest would then to be a smoke test, and hook up INPA and fun diagnostics