This may turn out to be embarrassing. Yesterday, I went through the entire fuel system. Blew out the lines from tank to carb. No obstructions with good flow from the pump. Removed the floats, no leaks. Cleaned the float valves, nothing sticking. Cleaned the bottom of the float bowls, just a little dirt, nothing major. Blew out the jet tubes, no obstructions, Removed the dashpots and pistons, cleaned them. Working fine. Got everything back together, started right up and ran super for 30 seconds ... died. This whole thing started when I was flushing my cooling system and had removed the thermostat and replaced the housing without a new gasket. I was loosing some water, but nothing major. When I looked a little closer, the coolant was spraying out on the spark plug side. I stuffed a shop rag over the thermostat housing to stop the spray and the car continued to idle. As it warmed up it sounded a little healthier. So here's my latest guess. It was taking about 30 seconds of coolant spray to ground out the #1 plug and kill the motor. After it sat for a bit, the water dried up and everything was fine until the water sprayed out again and killed it. After plugging the leak and heating up the motor, all the water dried out and it started to run better. Won't know for sure if this was it until Sunday or Monday when I've finished flushing the cooling system with a nice citrus flush
https://dieselgiant.com/mercedes_citrus_flush.htm, button everything back together with new thermostat and gasket and see if it's been fixed. Anyway, I know I have a nice clean fuel system and cooling system.