Replacing the Fuel Pump on a 420 SEL 1986
 

Can anyone tell me how to replace a fuel pump on a 420 Sel (1986) ? Is there or are there any special things that I need to look out for. Please dont tell me it is in the tank! Help!

Its been too long since I replaced one for me to give you specific info. But as I remember it was straight forward. The one I did (300SEL6.3) was next to the tank, not inside.

Putting the pump in the tank is the most hairbrained thing I ever heard of. Don't the people who do dimwitted things like putting the pump in the tank realize how much shops charge an hour and because of stupid designs take 5 times a long to fix? It the car manufactyres had to pay the repair costs, which usually are beyond the warranty, maybe they would design for easy serviceability.

When I worked for IBM, reliability and serviceability was always a design criteria. Since many of IBM's machines were rentals, it was to IBM's advantage to have the fewest breakdowns and when they did happen, the machines had to bequick, easy and economical to repair. Not so with the car companies.

~~~~~~~~~~~~~~~~~PEH~~~~~~~~~~~~~~~

YOUR FUEL PUMP PACKAGE IS UNDER THE CAR AHEAD OF THE RIGHT REAR AXLE (PARTIALLY COVERED BY PLASTIC COVER).
YOUR 420 HAS TWO FUEL PUMPS AND DETERMINING WHICH ONE IS BAD CAN BE TOUGH,USUALLY THE LOUDEST ONE IS BAD.
SIMPLE TOOLS ARE REQUIRED(PHILLIPS SCREWDRIVER,7MM AND 8MM WRENCH,TWO 17MM WRENCHES AND 10MM SOCKET ON LONG EXTENSION.
KEEP A FIRE EXTINGUISHER NEARBY AND NEVER USE A DROPLIGHT AROUND GASOLINE
MF

Thanls that really helped a lot...Everything is in a nice neat package (pumps, filter) and it does not look as bad as I thought...Will work on it tonight and keep you updated. Again, thanks a lot.

Just did my 560 SEL
 

Just changed my 2 fuel pumps, fuel filter and bracket that holds all of them together. The pumps, connecting lines, and filter were corroded so bad it was unbelievable. So was the bracket. When you change the pumps and/or fuel filter - there is a plastic sleeve that goes on each one to insulate them from the bracket and they are supplied with the new parts. MAKE SURE YOU PUT THEM IN. Someone had worked on this package before I got my car and all the corrosion was due to electrical reaction (I believe my mechanic said Galvanic reaction) between the aluminum filter and pumps and the steel bracket. He also told me the plastic insulators are there the prevent this. Make sure they are installed correctly!! Other than that - it's really a very easy job. Even though the connecting lines were convoluted, God bless Mecedes, they go together beautifully when properly aligned. No bending a little to make fit like some North American Cars.

Just wondering why there are 2 fuel pumps on a MB 420???? I have a 300SEL6.3 and that can burn 20 gallons per hour at top speed and that only needed one fuel pump to supply all that fuel. ~~~~~~~~~~~~~~~~~~~~PEH~~~~~~~~~~~~~~~~~~~

Why 2 pumps
 

Not knowing for sure - but using common sense -since the pumps are hooked up in series - I believe it is to get the proper pressure to the fuel distributor.