1999 C280 cranks but no start
 

I did see some post related to this but never with a definative answer so I am hoping someone has resolved this issue on their own vehicle.
I have had two instances where my 1999 C280 sport would not start, about 2 weeks apart. In both instances the carwould turn over very fast, I believe the battery is good. It will turn over for about 5 seconds then stop, I think this is its normal function if it cannot fire. I do not smell any gas at the rear of the vehicle.
In both cases I got in my car to drive for lunch. The car started normally and was driven less than 1 mile away, approx 2-3 minutes and parked. When I came out , the car would not start. The first time it started after 5 minutes of trying. The second time it would not start so I got a ride back to work. I went back to the car about 1 hour later. I brought a wrench and tapped around the gas tank and fuel lines. It started. I am not sure whether the tapping did it , I was thinking fuel pump.
Any ideas? Where is the fuel filter? I have had the dealer say crank position sensor but he got no codes when testing. I cannot believe the computer will show 2 year old codes but cannot code a problem 1 day old!!! Can anyone confirm, will a crank position sensor code up 100% of the time? What about low fuel pressure do to filter or pump issues.

RE: 1999 C280 cranks but no start
 

a crank sensor does not always throw a code, actually rarely. if the car is hot and wont start, but when cold it does, that is probably your problem.

RE: 1999 C280 cranks but no start
 

thanks. Any idea why when its hot it won;t start versus cold? Also , my feeling is the car is not all that hot. For both times that it would not start the car was driven only 1-2 minutes to a diner for luch after sitting for 4 hours in my company's parking lot. I am not sure it would get to that high of a temperature. Especially after driving 1 hour to work.