2005 e320 doesn't start sometimes
 

My sister has a 2005 e320 and has had this problem for awhile. When she turns over the key the car doesn't crank so it won't turn on, so we turn the key upside down and try to start it again and it works. We've taken the car to a guy who specializes in German cars but he couldn't identify the problem unless it didn't start right in front of him. This happens once like every 15 or 20 times we start the car.
Any ideas would be awesome!

if you think it's the key, replace the batteries in the key...
 

the owner's manual explains how

I don't think it's the key because we've replaced the batteries and it still happens

If you have the other key, you might want to see if it is specific only to that one key.

Ok thank you, ill try that and see.

The change of key didnt work because it didnt start again

That would pretty much rule out the key as the issue, then.

Does it work every time that you flip the key over, or only some of the time?

It works most of the time but every like 15 times we start it, it doesnt crank and the other day we couldnt get it to work for a half hour and when we finally got it started we took it to a place to check the battery and the battery is fine

It might either be your camshaft or crankshaft position sensor. is their a check engine light? Mine would start intermittently and the check engine light would go on and off so I had it scanned and it said camshaft position sensor. The sensor is not cheap and it's easy to install so if you're a diyer i'd highly suggest doing it yourself

Re the Crankshaft PS suggestion-does it happen when the car is warmed up, and then you have to wait a while until it cools down before it will start again? Or does it happen first time-when the car is cold?

good point that was another symptom i had that i forgot to mention

it happens when its both cold and warm, but usually we just take the key out and try again and it works

and yes the check engine light does come on

The obvious next step is to get the code read and see if that shines any light in a particular direction. Did the tech you took it to scan the code? Was the CEL on when they looked at the car? If it was maybe a different shop is in order -- dealer may be your best bet.

+1 on getting the codes read.

you can use any generic obdii scanner to find out the codes. no need for the star diagnosis. take it to autozone, I believe they'll scan it for free. I have a bluetooth obd scanner that I connect to my phone and that is how I found out my codes so you cando it with any obd scanner. Other functions you would need star diagnosis for.

What did you find out ? Thanks. I'm having that problem also.