Hi, my most recent issue with my benz is that it wont start, sometimes. When it does start it runs for a little while and then kind of putts for a little bit and then dies. When it DOESN'T start, it turns over and seems like it's backfiring and I can smell a pretty strong smell of gas. Anyone know what this might be? and how much it might be to repair?

How many miles? It sounds like you have fuel with intermittent ignition. Off the cuff guess but if the CPS is original this may be the problem. Mark

I have about 150,000 miles on the car. I just called the local benz dealership and they said it could be the distributor cap, "it could be dirty and crusted up if it's old".

Start with the easy bits first. The distributor cap, rotor, and ignition wires are all suspect if not replaced within the past 60K miles or 5 years or so (plugs within the past 12K miles) but defects in these should cause a consistent problem. The resistor on the rotor frequently fails. Also the OVP can cause intermittent symptoms like you report (many posts on this). After confirming these parts are good move on to troubleshooting the more expensive/time consuming items. However, the backfiring through the intake manifold is indicative of an ignition timing issue which could be caused by a defective rotor, EZL or CPS among other candidates. Mark

ok, what's an "OVP", "EZL" and "CPS"??

OVP is over-voltage protection relay, EZL is the ignition control unit and CPS is the crankshaft position sensor. Search this site for more information than you will care to know on these subjects. Mark