E420 will probably have a MAS relay (combined) rather than a separate fuel pump relay (electronic vs KE-Jet fuel injection).
No, I would not replace fuel pumps on a program, wait for them to die, as many go 300,000 miles or more, and condition can be easily tested by measuring current draw.
Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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