After searching the information about the Fuel Pump Relay, I decided to go ahead and buy one.
My wife insisted that I had bought something about 3 years ago for the MB, didn't know if it was the problem, but replaced it anyway. So I went looking in the truck for any parts. I always save a spark plug and the box it can in, and an old part in the box of the new part for a little while, just in case.

I looked in the truck, in a small box and found a box, it says Fuel Pump Relay. I did replace it when I had another small problem a few years back. In the box was the original fuel pump relay. I pulled the replacement FPR and reinstalled the original relay and the 420 started right up. I guess the old relay was not defective after all.

The replacement FPR was made by KAE. I don't think I'll buy another KAE brand. The original FPR is 19 years old and still working, the KAE fuel pump relay part only lasted 3 years or so, and let me on the side of the road.

The MB is running great again, thanks for everybodys help!