Will this fuel system bypass tool work on '90's models?
 

https://surrauto.com/kits/tfs203-2/

I have a few cars that have sat for a while and now crank but won't start. 94 E420, 94 C280, 89 300SEL for example. They do run a second or two with starting fluid so I suspect fuel pump inop. Would this tool be compatible with the fuel injection systems in these cars? Both as a diagnostic aid and just to get them running so I can move them around.

nice tool

I'm guessing it would work on the cars you listed except for the 89 300SEL since it works by pressurizing the fuel rail. The 1989 300SEL does not have a fuel rail.

Perhaps it could be adapted to pressurize the fuel distributor but I don't know where it could be connected???

Good luck!!!

It doesn't have tap/schraider valve to test fuel pressure?

It would seem that on systems that have a return fuel line, and the system pressure is regulated on the return flow, that the return would have to be blocked, so that the rather small volume of fuel available in the canister is not sent to the vehicle tank.
In that case, fuel pressure control would be accomplished solely by pressurization of the canister.
In the case of K-Jetronic systems the required fuel pressure will vary from ~75 psi to ~95 psi, depending on system version.