I will definitely check the OVP. And while I am back there, will check the fuel relay, though I really don't know what to look for other than dirty electrical contacts.
The ignition coil was replaced exactly three years ago and I assume their lifespan is longer than that. The battery is new. OVP and fuel pump relays are about 3 years old also.
Fuel pump(s) are in good shape. Fuel filter has not been repalced in a while. Accumulator, as far as I can tell, is fine -- never had any pressure problems.
Spark plugs are due for replacement but are probably not part of this problem.
Distributor cap and rotor and spark plug wires are the only components that have not been serviced, replaced or even given much attention in at least five years - and may indeed be original equipment -- and thus seem to be the most likely suspects.
2001 E430 4matic
Gone but not Forgotten:
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black