1977 280E Fuel Injectors

I have a 1977 w123 280E with fuel injection. The car runs pretty good but if I park it for a few hours and then try to restart it, it takes a lot of cranks to get it running and puffs black smoke after it's started. I suspect that fuel leaks out of the injectors into the cylinder (flooding it and making it hard to start when hot). I also suspect that if it sits over night all the gas drains through the piston rings making it easy to start when cold.

Is there a common reason for these injectors to leak? There are a lot of "parts" available for the fuel injectors (o-rings, holders, injector asm, etc). Not sure exactly how these work but looking for some advice if anyone has experience with this and what parts might need to be replaced.