actually I'd go with new plugs and a coolant temp sensor, the coolant temp sensor is a very important and often overlooked issue......

Geez!....there are so many things that can go wrong here, I think i will just tow it home and go out and get a Buick and work on the 300E at my leisure as time and money permits. Seemed like such a simple thing, but those crazy Germans and their cars! No one can figure out whats wrong, its the the Jack in The Box commercial where Jack asks if anyone knows what hes putting in his bowls....and so many different answers start coming out. The mechanic is jetronic trained and has worked on many Benzs and he cannot figure it out, says the car should start!

did you ever consider your injectors shorting out, that is a major cause in alot of cars, because the injectors in old cars fire all at once so if one is not working then they all will not work, that is what happened in my friends late 80s buick. just unplug them one at a time the car can run on 3 cylinders! and also check the difference in oms (resistence) between them if the resistance is higher then the thing is burnt out. and if anyone needs someone that can solder parts I can sure do it just give me a few bucks i dont want much

Injectors shorting out?
 

:(This car is a CIS, and I dont see any electrical connectors going to each injector, just a commor rail and individual injector. COuld the accumulator be bad? I have heard that it could build up pressure and then fail and the pressure would be lost. I am just so frustrated after 10 days of not being able to find out why, when it starts, its very smooth for the 5 seconds and then nothing but cranking and no start. A little ether ...starts right up and then dies. Something is telling the fuel not to go to the injectors....

Fuel pressure? Fuel pump staying running? Fuel filter checked? (might be clogged) The temp sensors can make all the difference.

Crank position sensor?

They're really not that complex.....

The injectors are mechanical.

I had to work on our 300E for a while to get it to run properly....but if you check everything, it will work.

New fuel filter, pump shuts off after about 5 seconds, it is just weird. I am taking it to a new mechanioc this week. This guy just doesnt seemto care about fixing it and I need my car for business!

In my opinion getting them repaired at the dealer is well worth it....they are most likely to know how to fix/diagnose it.

Again... Its the fuel pump relay. Pick up one at a junk yard.

Or take the car to a Benz mechanic. Few others can diagnose the problem.

I put in a NEW MAS relay...now dufuss mechanic says he cant fix the car and to get it out. Fuel pressure at FD is 45 psi, 85 at pump....thats about all he can tell me other than he cant fixt it. I am getting it out asap.

Did this ever get fixed?

It would appear as though you haven't actually mentioned which model you have, maybe I missed that, sorry...refresh my memory please....thanks