Hello,

my car is a 2000 C230 kompressor

I am going back to the dealer this wednesday. I'm pretty sure that is the exact same problem I had last time.

First time I wasn't able to fill in gaz, they changed the shut off valve (part 000-476-70-32) and everything was fine.

Then a couple of months later, I got the low fuel light flashing, checked the fuel cap and it was fine. Then the CEL came on. After bringing the car to the dealer, they pulled out code "P0455 - Purge control system (major leak) or voltage supply of component B4/3 (Fuel tank pressure sensor)". They found out the shut off valve was staying open and changed it (unfortunately, this part is not covered under extended warranty)

This was in november. Now again a couple of months later I get the same thing... And I can bet 10$ it's gonna be the same problem.

Is it a frequent problem? Is there a cause elsewhere that could make my shut off valve fail like this?

I have a pulley kit with an upgraded fuel pressure regulator, can this be the cause? I don't think so since it runs fine for months before the problem occurs.

Any help appreciated. Thanks

Etienne

Upgraded fulel pressure regulator? hmmm seems like that may be a problem. The pressure/purge systems in an MB are very sensitive, I mean very sensitive, these types of problems are very common at kicking off CEL lights. Lots of times the purge valve fails, but in your case if you are getting incorrect tank pressure that could be due to the pressure regulator not being in sync with the rest of the system. What this system does it monitor the pressure in the fuel tank, once it gets to a certain level it opens the purge valve and bleeds off the pressure through the charcoal cannister where it stores vapors, these vapors are burned through the intake system. The pressure has to be maintained properly to prevent fuel tank colapse and over-pressure. I would suggest checking the purge valve. That new of a car the cannister is probably ok, but the purge valve can cause purge flow pressure issues, I had a CEL light come on several times, each time incorrect pressure and tried several things, I finally replace the valve over a $100 for the part. Also if that doesn't fix it i would get the operating parameters of your upgraded fuel pressure regulator and compare them to spec, that could cause a problem as well. Good luck!
B

__________________
Brian W. Heitman

www.MBCA.org/northtexas

Join MBCA!!!

Thanks a lot, I will check for the FPR specs. Altough dozens of persons have this FPR on the M111 on SLK230 (R170). Maybe on their car it doesn't trigger this problem.

Etienne

My "bigger" FPR part number is Bosh 0 280 160 575

do you think it could make a difference between the M111 in the SLK and the M111 in the C Class? It's the exact same engine.

Etienne

4.0 bar the new FPR

Altough I read more info on the P0455 code..

Description:
Possible Causes:
Is it possible with the system to detect if it's multiple small leaks that triggered the code or one large leak?

IMO, if it was my FPR, there would also be a coded P0456 which is "EVAP Control System Leak Detected (Very Small Leak)" [The PCM monitors the complete EVAP control system for the presence of a very small fuel vapor leak. The system failure occurs when a fuel vapor leak from an opening as small as 0.508 mm (0.020 inch) is detected by the EVAP running loss monitor test.]

Also, if it was my FPR, why would it run fine for months before it goes off?

I'm pretty clueless about all this. I could try putting bigger injectors instead of the FPR (one person did this on his R170), but I can't believe everyone has this FPR with the pulley on the R170 and on the C230 it would trigger an error.

Etienne

Wow,
looks like you have been tinkering with this one for a bit. I would recomend inspecting the entire fuel vapor system. Check the purge valve to ensure the connections are tight and that it is not stuck open. These are common to fail and easy to get at that is why it is best to check first. Have you done anything else to the car? just the new FPR, if they are on a different model but same engine should not be a problem, especially if the parameters are the same. Good luck!
Best Regards,
Brian

__________________
Brian W. Heitman

www.MBCA.org/northtexas

Join MBCA!!!

I have the fuel pressure regulator with a little larger crank pulley and a K&N air filter. nothing else changed from factory (engine). It is the same engine on the SLK, exactly the same (except SLK can have manual trannies, and an electric fan instead of viscous coupling one, and battery in the engine compartment...)

I appreciate your help. I will ask the guys at the dealer wednesday to maybe check more than just the shut off valve itself. Maybe it's effectively the shut off valve that fails, but then there is something that makes it fail.

And the shut off valve is not under warranty, fortunately, they don't charge is it's the same part that fails since it's like on the part's warranty. They might charge diagnostic time.

What is really bugging me is why does it fail after 6 months, not after like 3 days...

Etienne

I am not saying that it is your FPR, it is just likely since it is done aftermarket, It is just that if you have checked everything else that is likely since it is not factory. The purge valve is a common failing item and have them check that. Good luck!
Brian

__________________
Brian W. Heitman

www.MBCA.org/northtexas

Join MBCA!!!

when you mention the second time the shut off valve was the problem, which valve were you referring to this time ? the valve sitting on top of the canister or the MOT valve that does the purge which is under the hood ?
thanks. !

__________________
Whether you think you can or cannot, Either way you're right!. by Henry Ford.

Do you have a code for major or minor loss? The test event happens when all the perameters are met, Once that happens a valve is closed and another opened, the ecu times how long it takes to drop to a specified value. If within specs it then watches how long it takes to bleed down. The first test is major leak and the second in minor. They can be a real pain to find. I have changed a lot of fuel tank vent valves, located at the tank and a lot of purge control valves along with several tanks. I would think a dealer would be required to diagnose is based on the equipment needed.
Bill

Yes I have the p0455 code.

__________________
Whether you think you can or cannot, Either way you're right!. by Henry Ford.