I have been trouble shooting a hard start problem on my 300CE. The hard start takes two to three tries, or it would stall as soon as it is started. There are no fuel smell under the hood.

Here is the symptom:
Hard start in the morning, or after a few hours
No problem if stop for a few min, such as refill gas at a gas station

What have been done.
Adjusted EHA valve, small black box behind fuel dist
Swapped out EHA valve and fuel pressure reg with another car
Replaced fuel filter and fuel accumulator

Jack