Same thing happened to my '88. Don't throw parts at it until you know exactly what is wrong. Buckle the seat belt, open the R window and turn the key. If you hear the fuel pumps running, you are o.k. there. If you don't, you may have a bad fuel pump relay. Lots of threads on that subject.
To isolate quickly the ignition system, add an ounce or so of fuel to the air intake (remove the air cleaner) and crank it over. If it starts and runs momentarily, the ignition is o.k. and you are probably not getting any fuel to the cylinders from the fuel distributor. Diagnosis of this problem really should be done with a pressure tester, which usually is only available at a MBZ shop.
We never really found what caused my problem as my mechanic ran all the tests and couldn't figure out what was causing my no fuel problem. He finally was pouring raw gas into the air intake while his helper was pushing on the accelerator. The car let out a huge backfire and has run just fine ever since??????? Good luck with yours.
'85 300 SD, 165K-Sold
'88 300 TE, 165K-Sold
'64 Porsche 356C Cabriolet
'86 560SL 124K Miles
'94 320E Wagon, 74K Miles