FCSmthree

Hello, hoping someone can help out, my Dad has a 95 SL500 and recently came up with an issue where there is no spark on cylinders 1, 4, 6, and 7.

Spark plugs, spark plug wires, cap and rotor, coils all replaced. Found no spark on the right side of the distributor.

We're stumped after replacing all of these parts, any ideas of what it could be?

I searched and searched, but the resolution were the parts we replaced.

Any ideas of what is causing this? Thanks in advance!