1995 c280, engine cranks, cranks, cranks and cranks but does not fire in the morning. it starts after 4-5 attempts, each attempt with waiting at key position 2. when it starts, it drives perfect like, well, benz. never any problem with warm start. warm start always on first attempt. changed ovp relay, no relief. changed camshaft position sensor, no change. changed fuel filter, no difference. my next step is to get fuel pump changed by mechanic. anything else, i need to do prior to fuel pump change??

no cel, went to autozone and scanner revealed 2 codes - P0400 Exhaust gas recirculation flow malfunction and P0505 Idle control system malfunction. today is the first time i had appropriate experience with cold start after egr valve cleaning yesterday. i recorded in mp3 format. http://www.youtube.com/watch?v=WDrQCmD3tio first sound is when i wait at position 2 (first 4 seconds) second sound comes from passenger side rear end that starts at 7th second into this audio clip and ends at 10th second. sometimes i don't hear second sound. car does not start if second sound is absent. at this moment i have no idea what these sounds mean. hopefully, some of you will be helping in this regards.