My 93 mercedes will not start sometimes, it turns over but will not start

Hi,good day,your model have two engine gasoline and diesel engine,,for diesel engine check your pre-filter and main filter,fuel and air leak,check your engine shut-off,if not corrected,send (check) your injection pump and nozzle in calibration center,,,for gasoline,sop,,you have to check fuel pressure,,fuel filter,fuel pump,fuel pump relay,,coil,spark plug,cable,transistors box,ty