300E Fuel problems

[Razor]

Greeting,

I've been having some problems with fuel delivery on my 1989 300E with 171,000 miles. During initial startup, the engine seems to only run on a few cylinders, then after a few seconds the rest start firing. Sometimes while motoring down the road the engine would just stop, rendering me stranded. I would try restarting the engine right away without success. After a few minutes I tried again and it would start. This has happened several times over the last 5 months.
Three weeks ago I couldn't get it started at all. I've looked at and removed the fuel pumps and the accumulator for inspection and testing. The pumps seemed to be pumping fuel, so I reassembled. After turning the ignition switch, I could hear the pumps working to pressurize the system. The engine started like nothing was wrong.
This past week I was left stranded again. I removed the aircleaner and cracked the fuel line in and out of the injection pump. Initially I had some residual pressure, but then nothing. I tried to start it without any fuel delivery from the pumps.
1. Why did Mercedes need two fuel pumps on this model?
2. Will I need to replace both pumps? Not excited to spend $500+ for pumps.

Thanks for any help or suggestions.
Razor