1988 300sel fuel system
 

It's an 8 cylinder gasoline engine. I'm trying to find the fuel relay and fuel filter. There are 2 cylindrical things by the fuel tank ~6" long & ~3" dia. but I don't know if both are pumps...
Car's been parked for ~3 mths & won't start (starts & runs ~ 30 sec. with starter fluid), has at least 5 gal. in the tank, battery is fully charged.
Any assistance would be appreciated, thanks.

if they are pumps then they will have wires running to them ... anyway to see any numbers on them .. you can do a quick search for part numbers if they are readable .. when you turn the key does the pumps prime up ? do they buzz then shut off real fast .. buzz at all ?

if you have the time and tools beings you dont have that much gas in the tank you could remove fuel pumps and test them .. make sure they are pumping correctly ..

Are you sure about the car ?
 

The 1988 300SEL has a six cylinder #103 engine that has only one fuel pump .
I know my comment does nothing to solve your problem, but the right info can give people on this forum a better idea of how to help you.

Better check your engine compartment for the correct engine type.

which would make sense because those models have the fule pump on bottom and fuel filter on top ..

88 SEL 300 Fuel Prob
 

As some one else has already stated, the 88 SEL 300 is an in line single overhead cam six. The fuel pump and pulsation dampener are located beside the fuel tank. The filter is back upstream. It has been a whlie since I have worked on one. The filter might be inside the unibody reinforcemet near the engine (under the vehicle). As to your problem, it could be the filter, pump, relay (located in the electrical box by the firewall -you need to get a manual to determine which one) or it could be the regulator which is located near the fuel distributor. I would put a fuel gage on the line at the regulator (the manual will guide you as to the proper way of measuring pressure).

How bizarre.... I wonder what this car actually is? A 300SEL or a 420/560SEL?