The fuel pump relay can be removed and you can bridge the connection to test if the relay is the issue. Do a search for "300E fuel pump relay" and you should come up with something related to the diagnosis of the fuel pump. There are 2 fuel pumps on these cars (I assume this is the 300E you were referencing in the other post).

From your description, it seems like the issue is more electrical (e.g. ignition) and not fuel related. My car experienced similar symptoms and the major culprit was a bad ignition coil. On a side note, if you do change the ignition coil, make sure you unplug not only the battery, but also the plugs in the EZL ignition unit. My local mechanic said that if you leave them plugged in, you can possibly damage the crank position sensor, something that is not an easy replacement/fix.

Good luck

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87 300E
202k on the clock