***LOT of info here. Tried to go into detail the best I could. Cliffs:

-Car is EXTREMELY difficult to start when cold.
-Strong smell of gasoline after the car has been sitting.
-"Chuggs" when cold, as if missing when sitting idle in gear. Idles fine when in Park while cold.

See more details below:

Hey guys, I did a quick search, but it wasn't extremely helpful.

I've had my 500E for nearly a year now, and I've loved every bit of it.

About 6 months ago, it developed a difficult cold start; taking solid 25-30 seconds of cranking before turning over. This is when the car has been sitting over a period of about 8+ hours. After starting, it would "chug" a little as if it were experiencing a slight miss.. The "chugging" was only experienced while in gear. If placed in Park, the chugging goes away and the car idles normally.

(side note, while the car "chugs" there would be a loud "knocking" noise coming from what appears to be the rear of the car, under the passenger rear seat. Once warm, the "knocking" would disappear.)

After completely warming up (say the end of my commute), it would run perfectly fine.

Now, it takes a couple of attempts of 30 second cranking with a bit of pumping the gas to start. It will backfire quickly before struggling and will weakly start.

There is also a VERY strong smell of gasoline when the car sits. There is a faint smell of gasoline when driving, but I think this may just be the smell lingering since it was so strong while sitting still. I've never experienced the smell until recently, when it became extremely difficult to start when cold.

There is no smoke on start up, even when cold.
The plugs do not look foul. Excessively burnt or carboned up. (Although they do appear to be a bit more "Tan" than usual with a hint of corroded "green?")

There appears to be no leaks, at the FPR, Fuel Rail, or injectors.

Please give me a hand. I love her, and at the moment, shes my daily! Quite embarassing to sit in the parking lot at work and struggle with such a pretty car

***LOT of info here. Tried to go into detail the best I could. Cliffs:

-Car is EXTREMELY difficult to start when cold.
-Strong smell of gasoline after the car has been sitting.
-"Chuggs" when cold, as if missing when sitting idle in gear. Idles fine when in Park while cold.

See more details below:

Hey guys, I did a quick search, but it wasn't extremely helpful.

About 6 months ago, my 500E developed a difficult cold start; taking solid 25-30 seconds of cranking before turning over. This is when the car has been sitting over a period of about 8+ hours. After starting, it would "chug" a little as if it were experiencing a slight miss.. The "chugging" was only experienced while in gear. If placed in Park, the chugging goes away and the car idles normally.

(side note, while the car "chugs" there would be a loud "knocking" noise coming from what appears to be the rear of the car, under the passenger rear seat. Once warm, the "knocking" would disappear.)

After completely warming up (say the end of my commute), it would run perfectly fine.

Now, it takes a couple of attempts of 30 second cranking with a bit of pumping the gas to start. It will backfire quickly before struggling and will weakly start.

There is also a VERY strong smell of gasoline when the car sits. There is a faint smell of gasoline when driving, but I think this may just be the smell lingering since it was so strong while sitting still. I've never experienced the smell until recently, when it became extremely difficult to start when cold.

There is no smoke on start up, even when cold.
The plugs do not look foul. Excessively burnt or carboned up. (Although they do appear to be a bit more "Tan" than usual with a hint of corroded "green?")

There appears to be no leaks, at the FPR, Fuel Rail, or injectors.

Please give me a hand. I love her, and at the moment, shes my daily! Quite embarrassing to sit in the parking lot at work and struggle with such a pretty car!

If you can't locate the fuel leak in the engine compartment you should check around the fuel pumps at the rear of the car. The crush seal between the check valve and the pump are bad about leaking, which could be causing a lose of fuel pressure and difficulty starting.
The original crush seals were a thick copper seal which is replaced with a thin seal. Part #007 603 010 112. Use great caution if you are going to attempt to reseal the pumps yourself.( Strong possibility of massive fuel spill.!!!)

Also you say you checked the fuel lines and pressure regulator on the fuel rail, did you pull the vacuum/bleed line off of the regulator and check for fuel there? There should be NO fuel in the vacuum/bleed hose, if there is then the regulator is leaking and needs to be replaced.

Good luck, Robert

__________________
Mercedes Benz Master Tech - Retired

Thank you kindly, Robert!

Once upon a time (about four months ago) One of the pumps was extremely noisy. Took it to my mechanic and found one of the fuel pumps was leaking! The pump was promptly replaced, the other appeared to be fine and the noise stopped (not related to any noise ive mentioned above)

I've pulled the vacuum line from the regulator and found no fuel, however I didnt sit and wait for fuel to escape, it was just a quick glance then I popped the line back in.

I will have the other fuel pump inspected. Thanks!