andruxa69

Hello, fellow MB owners,

I have a CLK320 here, that has been relatively trouble free for almost a year, however, now have a problem: Check Engine is on.

I have purchased a simple code reader/eraser from fleabay, and have been receiving consistent reading of the same code:

0455 Purge system major leak, fuel tank pressure sensor voltage supply

I have searched several topics, and while there seems to be fair amount of info out there, my expertise is somewhat limited to mechanical tasks, such as replacing struts, brakes, or other non-electrical components.

What do I need to replace?
Anyone willing to hold my hand?

andruxa69

I have replaced the Gas Cap, reset the error code. Soon after starting to drive get the LOW FUEL indicator flashing, and while Check Engine light is not on, the code is back (0455).

Does anyone have idea on what I could try? I do not have access to smoke machine.

MarcusF

This sounds like a vapor recovery failure. Unfortunately, I understand the theory of how it works a lot better than I know where the parts are on this particular car. The way most vapor recovery systems work is this – gasoline vapors are captured in a storage container. When the car is running in closed loop mode (at cruise or idle and being monitored by the O2 sensor), those captured fumes are inhaled through the intake system. That’s called a purge cycle. In addition to keeping track of purge cycles, OBD-II tests the vacuum system used to capture the fumes. To perform the test, most systems create a vacuum in the system and then check to insure the vacuum doesn’t leak down too quickly. If it leaks too quickly, OBD-II registers that as a problem. One common way leaks occur, is when the gas cap isn’t tight, but you’ve gone over that. Another way is for the line to the charcoal canister to leak.

According to the MB Service DVD, the fuel tank pressure sensor is in the tank, and appears to be part (or bolted on) the fuel level sensor. As an aside, are there multiple level sensors? The DVD says the right one, which appears to be on the driver’s side – opposite of the fuel filler (which isn’t right to me, but if they say it is, who am I to argue?). Although physically in the tank, it appears to be accessible from the top (trunk), which is common.

The DVD says to check the fuel tank pressure sensor, and purge control valve (which I believe is also known as the charcoal canister shut off valve). It sits between the charcoal canister and the intake manifold – probably under the hood.

The DVD says to perform the test steps according to Diagnostic Manual “Engines, volume 4, section 9”. Sorry, if that section is part of the DVD or the WIS, it isn’t overly obvious.

Confused? Me too. First I'd make sure the electrical line running to the fuel tank pressure sensor/fuel level sensor was secure. Next I'd check the line to the charcoal canister (after finding where they've hid it). Then, unless the fuel tank pressure sensor/fuel level sensor and the purge control valve are dirt cheap, I’d take it to the dealer. For me, anything else would be simply tossing parts at the car and hoping something sticks. You could also try the tech talk section.

In either case, post back and let us know what the solution was. Thanks

MarcusF

One last note, you have driven it a while with the new gas cap on, right?