My 2004 w211 wagon has just spent two days at a Certified Emissions Repair Centre in the State of Connecticut in a FAILED attempt to diagnose and repair a persistent P0455 (large EVAP leak) error. Electronic diagnostics pointed to a stuck (open) rear shut-off valve. I had already replaced this less than a year ago...but they replaced again. Within 2 miles of driving the "fuel cap" warning came on, followed by a CEL and the same P0455. They then did a full smoke test. Found nothing at all. Engine monitors all come up good. But we still have the fuel cap warning (which comes on mostly when sitting in traffic after a short highway run) and the CEL. The supposed expert Emissions repair centre have run out of ideas...refunded my money, and told me to try the dealer (not doing that..)
Does anyone have any useful similar experience or knowledge to share? I am not (yet) a benzninja member....does anyone have an opinion as whether this is something he could crack?....
I've got 45 days left before this car becomes illegal on CT roads unless I can solve this...so all constructive ideas very gratefully received!!
You dont mention replacing the fuel cap with a new cap. Did you get a new cap?
My only experience with the fuel system was for a small leak in my W204 which turned out to be the purge valve and easy fix. I dont have a W211 so im just taking guesses.
My first step is looking up that code and seeing what info there is on it. I'll post what I found for P0455 below.
So besides the fuel cap and shut off valve have you checked all the lines more specifically the hose clamps. Looking at photos there are a few.
Have you checked the fuel tank pressure sensor. I mention this because the manual says to check the fuel pressure sensor. By actuation and checking voltage.
My 2004 w211 wagon has just spent two days at a Certified Emissions Repair Centre in the State of Connecticut in a FAILED attempt to diagnose and repair a persistent P0455 (large EVAP leak) error. Electronic diagnostics pointed to a stuck (open) rear shut-off valve. I had already replaced this less than a year ago...but they replaced again. Within 2 miles of driving the "fuel cap" warning came on, followed by a CEL and the same P0455. They then did a full smoke test. Found nothing at all. Engine monitors all come up good. But we still have the fuel cap warning (which comes on mostly when sitting in traffic after a short highway run) and the CEL. The supposed expert Emissions repair centre have run out of ideas...refunded my money, and told me to try the dealer (not doing that..)
Does anyone have any useful similar experience or knowledge to share? I am not (yet) a benzninja member....does anyone have an opinion as whether this is something he could crack?....
I've got 45 days left before this car becomes illegal on CT roads unless I can solve this...so all constructive ideas very gratefully received!!
Evap leaks are tricky to find visually or by trial and error. If there is a leak, a smoke machine will detect it in less than 2 minutes, as smoke will be emitted from the leak. Sometimes, a cracked hose is hidden under the car, a cracked component housing, or other issues.
So, the problem I'm having is that we've done a full smoke test and there are no visible leaks. Yet we still get the "large EVAP leak" error. This might indicate a number of issues...for example...1. did the supposedly expert shop do the smoke test properly?, 2. is this a sensor issue rather than a leak, or 3. is this intermittent (maybe a hose is cracked and expands with heat?) I need an expert to help untangle what I see as contradictory indications....it appears to be a sensor fault because there is no leak...BUT...why does the error only occur when I've sat in traffic for more than 10 seconds after the car has warmed up....that suggests an intermittent leak occurring under specific conditions. Has anyone seen this specific situation?
I should have mentioned...I'm on gas cap#3 (original came with the car a year ago. an aftermarket one, and a MB one) and I've repeatedly cleaned the gas cap and filler area with WD40. We've replaced the rear shut valve 3 times, and the charcoal canister once. There is no smell of gasoline anywhere, and I have checked under the rear seats. This weekend I plan to change the front purge valve and the fuel pressure sensor and check hosos as much as I can visually. Any other ideas??
So, the problem I'm having is that we've done a full smoke test and there are no visible leaks. Yet we still get the "large EVAP leak" error. This might indicate a number of issues...for example...1. did the supposedly expert shop do the smoke test properly?, 2. is this a sensor issue rather than a leak, or 3. is this intermittent (maybe a hose is cracked and expands with heat?) I need an expert to help untangle what I see as contradictory indications....it appears to be a sensor fault because there is no leak...BUT...why does the error only occur when I've sat in traffic for more than 10 seconds after the car has warmed up....that suggests an intermittent leak occurring under specific conditions. Has anyone seen this specific situation?
I should have mentioned...I'm on gas cap#3 (original came with the car a year ago. an aftermarket one, and a MB one) and I've repeatedly cleaned the gas cap and filler area with WD40. We've replaced the rear shut valve 3 times, and the charcoal canister once. There is no smell of gasoline anywhere, and I have checked under the rear seats. This weekend I plan to change the front purge valve and the fuel pressure sensor and check hosos as much as I can visually. Any other ideas??
If the issue is intermittent, it must be diagnosed "live", exactly when it occurs, and the smoke test must be performed while the error is triggered. Changing parts is not always the best way to fix random issues since new does not mean good/nor better and we may introduce other errors: like disturbing an area and suddenly it seems fixed (temporarily since we did not do it explicitly)
If the issue is intermittent, it must be diagnosed "live", exactly when it occurs, and the smoke test must be performed while the error is triggered. Changing parts is not always the best way to fix random issues since new does not mean good/nor better and we may introduce other errors: like disturbing an area and suddenly it seems fixed (temporarily since we did not do it explicitly)
Conceptually I agree that the smoke test must be performed while the event is triggered...I just can't work out how to strap the smoke machine and tech to the outside of the car while driving!
Conceptually I agree that the smoke test must be performed while the event is triggered...I just can't work out how to strap the smoke machine and tech to the outside of the car while driving!
I did not mean it that way, but arrive wherever the machine is, do not turn the car off, and connect it. Assuming it is possible.
Say, you have the machine ready, Take the car for a ride waiting for it to happen, i.e. reproduce it, then return to the test site (machine location), connect it and track the leak (if there is really a leak).
Even w/o the machine, once the CEL comes up you may need to connect the scanner before turning the car off and monitor live data looking for what triggered the light , i.e. "the event".
If it were easy, the mechanic or you would have solved it already.
I did not mean it that way, but arrive wherever the machine is, do not turn the car off, and connect it. Assuming it is possible.
Say, you have the machine ready, Take the car for a ride waiting for it to happen, i.e. reproduce it, then return to the test site (machine location), connect it and track the leak (if there is really a leak).
Even w/o the machine, once the CEL comes up you may need to connect the scanner before turning the car off and monitor live data looking for what triggered the light , i.e. "the event".
If it were easy, the mechanic or you would have solved it already.
I dont think its an intermittent fault. The problem is there, its just the requirements for the cars test procedures arent always there. So the car isnt always testing for it.
I dont think its an intermittent fault. The problem is there, its just the requirements for the cars test procedures arent always there. So the car isnt always testing for it.
He suggested it is intermittent, which I take as a matter of interpretation. The OP does not see any consistency in when it occurs, but I am sure there will be an explanation. Once the root cause is found, it would be "OBVIOUS" why it was happening.
Searching around for that code i've seen others say replacing the purge valve has gotten rid of the code. Worth a shot since its not that expensive. Also inspect all the hoses to and from the purge valve since they can get brittle and break. When I had a code for the evap leak I only had a generic scanner so guessed what the issue was. I bought the purge valve off eBay for $40.
Not sure id use wd-40 on the gas cap since i think it may interact negatively with the rubber seal. In the manual there is a note about using a silicone paste on the cap.
I decided to take a look at the work done by supposed experts, before delving into other parts of the system to find my P0455 large EVP leak error. See below - The shut off valve was completely detached! Looks like they installed it without the O-ring....and vibration caused it to come loose...so no wonder I still have a "large leak". The unfortunate consequence of the valve being detached is that it was hard for me to get gas in the tank....clearly because the tank couldn't vent without the valve attached....so the charcoal canister filled with gas and is now clogged. So although the shop refunded my money, their crappy work has now ruined my canister...and these canisters are made of unobtanium. Luckily, I had bought a used canister a few months ago, and installed it today with a new valve.
Now...for the first time in a year I am getting a different code. Until now I was getting P0455 (large leak)...NOW I am getting P0446 (EVAP Vent control circuit). I regard this as good news and next I will check and clean the electrical connections on the shut-off valve. Then test. After that I will work on replacing the Purge valve. After that I may replace the Tank pressure sensor. After that it's hoses. One step at a time... If anyone has a moment of brilliance to share please do so. (and thanks to all for the contributions so far...)
BTW...for anyone who happens to be in Connecticut....the shop concerned is Hank May's in Norwalk. They've been great in the past, but really let me down on this one.
This is how the "professional" State certified emissions shop left my shut off valve
Replaced Fuel cap
Replaced rear shut-off valve, O-ring, and pigtail harness (4 times!!)
Replaced charcoal canister (with a tested used one as new are no longer available)
Replaced fuel tank pressure sensor
Replaced front purge valve and clamped connections (they were loose)
If im reading the info below right it may point to a voltage issue. With your scanner can you function test the canister shutoff valve, test the connector for voltage and ground.
