85 500SEL Surges on fuel demand and on highway
 

Sometimes there is noise from the fuel pump, sometimes not. I used compressed air to back blow the lines with limited success.
It idles fairly smooth for 225,000 miles and runs fine otherwise, except for this problem. Is there a strainer in the fuel tank? What else should I check? I looked for a vacuum leak and did not find one.

There is a small strainer at the fuel distributor where the fuel line connects. It is integrated into the fitting in the fuel distributor. You might replace it since you have so many miles on the car.

Checked that strainer, there is no clog there
 

Is there any other strainers in the system or could something be clogging the outlet at the tank?

Not aware of any others. Disconnect the fuel supply line at the distributor and measure the flow. That should tell you if there is a problem. Could be anything, pumps, filter, crud in the tank.

Thanks again...last question (maybe)
 

Fuel pump and filter are new. If it is crud in the tank, how hard is that to get at? Does it take a tank removal or can you clean it while it is installed. I am doing the work on it.

I doubt that the tank needs cleaning. Im not sure I fully understand the symptoms. Can you be more specific as to that the problem seems to be. I understood from your first post that you think it is starved for fuel. If you are getting good pressure and flow from the fuel system then I would look elseware. Before I started fixing things that may not be broke I would get a good understanding of what the problems are. Can you elaborate a bit?

Im not sure what surging on fuel demand is.

85 500SEL surges
 

Yes there is another fuel screen,it is located in the bottom of the fuel tank where the fuel supply line attaches.
If the pump is noisy replace it before it leaves you stranded!
MF