c240classic

Its classified as a "Small Evap Leak".
Now i have done the obvious, i cleaned up the gas cap seal and put it on. Cleared the code, came back after 3 days. Got a new Gas Cap, cleared the code, code is back after 3-4 days. Now i know the problem is not fixed because before when i used to open the gas cap, i used to get an audible "whoosh" sound. Now i dont get it anymore.
Now the car is working fine, mileage is fine as well, so i know the fuel system is pressurizing as intended but i am getting a leak somewhere. I was thinking if it was a purge valve issue, it would be a bigger leak? plus the puge valve is ticking and then shuts off then ticks, which makes me think it is working ok?

I dont have the schematics for vaccum lines for the fuel tank and the vents. Anybody have any good diagrams? or a service manual? Any ideas to get this issue resolved?
Thanks

Glyn M Ruck

Another one!!! We've had 3 in a couple of weeks

Read this thread. You need to have the system smoke tested under pressure by a competent shop. Can be the charcoal canister. Never use compressed air to check for leaks - it's extremely dangerous. I posted the diagram to this thread.

https://mbworld.org/forums/c-class-w...-cold-cel.html

c240classic

I read the post that you pointed to. I do believe you are correct that instead of throwing parts left right and centre, probably best to take it to a competent shop. I am not sure who can do a smoke test in my area, so i will have to check.
However here is my beef, i have an emission EVAP leak with no effect to daily driving, except an annoying check engine light. Now i have to get this looked at and possibly replace a charcoal canister or a purge or both. Possibly looking at $500 + for a few fumes releasing to the atmosphere? Oh well..
I am just trying to check all possibilities myself that i can before i take it to the stealership.
I got the diagram you have up there for the Canister .. It gives me two lines to check. One coming from the engine bay to the cansiter (is this line from the purge valve?) . Second is the one going from the canister to the fuel tank. So if there is a leak anywhere after the purge, in the cansiter or the return line to the tank it will not build vaccum, am i correct? Are there any one way valves in this loop?
How does the tank vent itself ?
Thanks for the help.

Glyn M Ruck

I have never been through this system in detail so I don't know. Your assumptions sound right. The car vents it's tank via the charcoal filter into the inlet system of the engine

splinter

Haven’t yet suffered your P0442 fate, so I’ve no first-hand knowledge of its potential resolutions. Your proper "centre" leads one to believe yours may not be a USA vehicle; they're all I have service information for in the reference library.

Perhaps these may prove useful before diving in further - or what confronts your technician:

DarthBudice

The real question here is what conditions or logic chain causes this specific code.
I see somewhere that "Small leak test starts when large leak test has created
-7mbar pressure. Y58/1 (purge control valve) closed. Pressure monitored by
B4/3 (fuel tank pressure sensor) for :30."
Also... "P0422 and 432 TWC efficiency":
ME continuously checks the signals if:
O2 signal after TWC >75% of O2 before TWC
~170 seconds
Then after 2 drive cycles, set check engine light.

Try checking for leak down with a hand-powered vacuum pump.
If a line (or component) can't hold 15-20 inches of vacuum for more than :30...
I've successfully diagnosed more issues with a $0.50 T-1 loopback plug than
I have with a $70,000 Digital Lightwave. Sometimes the simple tools are the best.

Good luck, let us know...

Glyn M Ruck

Thank you I don't have access to this sort of information. Taking this logic a step further. Do you believe it possible that with the EECS reasonably up to snuff that one could throw a 442 & engine light if the Cat performance or an O2 sensor's performance was slightly out of spec without throwing a 422 or a 130 - 160 range O2 sensor code? We keep chasing EECS problems for 442 codes & find nothing wrong but the car ends up generating a CEL. One of our moderator's cars has had a new charcoal canister & cap & been smoke tested. Nothing is found wrong but it throws a 442 which leads to a CEL.

drb930

[QUOTE=c240classic;3423911]Its classified as a "Small Evap Leak".
Now i have done the obvious, i cleaned up the gas cap seal and put it on. Cleared the code, came back after 3 days. Got a new Gas Cap, cleared the code, code is back after 3-4 days. Now i know the problem is not fixed because before when i used to open the gas cap, i used to get an audible "whoosh" sound. Now i dont get it anymore.

I did the same thing, cel comes back in a couple of days, same code.
Bought the repair CD for this, but haven't installed it on my computer yet.
Will subscribe to this thread and hope i can fix the problem and post what i fine.

Thanks,
Dave

BENZ0c240

what kind off OBDII scanner do you have that clear codes???

Glyn M Ruck

You can start with this little baby from Harbor Freight $50




What I use $150 - or very much more expensive

BENZ0c240

Glyn does the 1 you use clear codes?

drb930

I have the same one that Todd has and it clears codes-
http://cgi.ebay.com/ebaymotors/ws/eB...m=220348150464

Glyn M Ruck

Yep! Both those I have recommended clear codes - even the cheapy.

Glyn M Ruck

Never mind what you buy - most of these units are made by the same manufacturer in Taiwan. They will label & package them as required.

treiberg

Wondering if anyone ever resolved this...car failing smog because of P0456 (small evap leak). I hate to spend a bunch of money on a smoke test. If a couple folks will chime in on the remedy, it could save me a bunch of time and expense, I am hoping. I thought I could just celar code and get it smogged...turns out the CA smog system is smart enough to know the codes were recently set...it will fail if the car has not been driven at least 30 miles after the reset. Oooops! Know I really have to fix problem.

Glyn M Ruck

Two fixes I know of so far have been charcoal canister replacement & filler tube replacement if it's not the gas cap leaking. Phil our moderator has yet to solve his one but we fixed his rough running with a new throttle body.

mleskovar

I have heard of people having this problem after overfilling the gas tank and saturating the charcoal filter. Supposedly, if you continue clicking the fill hose after it automatically shuts off to get just a little bit more gas in the tank (topping off) you can cause this problem.

treiberg

OK, I took the inside wheel cover off to expose the carbon canister/fuel filler area. I just took a picture of my carbon canistor which looks very different from all the schematics I have seen in the books (most canisters look round and this is a squarish looking thing).

Anyway, I see a connection off the side of this thing with no hoses attached, is this normal? I think it actually is normal. I think it allows the purge valve to draw in air if it needs it.

All hoses look good and no obvious problems where a leak could occur. I am tempted to temporarily plug one of these hoses just to get thing to pass, but not sure where it thinks the leak is. Oh well.

drb930

Terry,

From what i have read on here when i was doing some research it seems common for the fuel filler pipe to get a leak.
I am tempted to remove the filler pipe and leak check it independently.
It would be easy, just plug the holes and make a connection for compressed air, and a little soapy water and we could e limit that item?

mleskovar

That has to be an air inlet, otherwise fuel vapor would be expressed into the cabin. It looks like it's mounted kind of cockeyed....or is it loose? Anyway, I think your assumption is correct. In a closed system with the gas being pumped out if you didn't add air the vacuum would become so great that the pump wouldn't work. Maybe try disconnecting that assembly and checking it for operation, it looks like it has an electrical connection going to it. Maybe blow into the inlet and apply power to the connector?

treiberg

Decided to spring for a new gas cap, and what do you know, the code has not reappeared since reset about 200 miles ago. Definitely worth the $25 bucks for a new one if that is all it was.

Glyn M Ruck

Great - Gas cap is often the reason - hold thumbs the code does not reappear.

drb930

You got lucky!

treiberg

Not so lucky. Put another hundred miles or so and code came back. So it was not the gas cap. I wish there was some cheap way to locate this small leak without an expensive leak test at the dealership.

LILBENZ230

Mine turned out to be leaking fuel filter neck. I'm not sure what this costs to repair, though, since mine was done under warranty.