Car has been in storage for 20 years. Started up about five years ago and was greeted with a neighborhood of white smoke. It was winter so we abandoned any plans to go any further.

Now, August, my son and I are attempting to evaluate whether all this down time has deteriorated the engine to the point of no return.

We unstuck fuel pump (rear). Inside of tank bad shape will boil out. We are bypassing the gas tank and using a plastic can.
Getting gas to the rail (manifold) and the cold start but not the injectors. Gas pressure appears, appears that is, to be sufficient.
We will check pressure with the key on and under cranking conditions. New fuel filter has been ordered.

My son is a diesel mechanic and I am no slouch either so not to much hand holding is necessary just some guidance.
Also, is the injection fuel system a K-Jetronic type otherwise known as CIS?

The injection system is completely mechanical, not a jetronic at all, very similar to a diesel injection pump.

if you have a diesel injector tester you can test the injectors to see whats goin on... I had to make an adapter out of an extra steel injector line to get everything to hook up.

good luck these mfi systems are a pain to fix if they aren't working right, and nothing is cheap $110 for an injector, and at least $600 to rebuild the pump

That chassis is MFI ...... Bosch Mechanical Fuel Injection.

First test is fuel pressure/volume at CSV. Looking for 1 litre/15 sec. flow rate.......

Thanks Senorunimog and Arthur for your replies.
The issue it seems is no fuel going to the injectors.

We have adequate fuel at the CSV, which is supplied from a tap off the return gas line. We haven’t measured it but with just a little cranking of the engine our fuel tank (plastic gas can) empties out in a few seconds indicating decent pressure.
After wearing out my mouse on all things Mercedes I have some thoughts thanks to the many forums and nice people like you.
My thoughts are to open up the rail (rack, manifold, thing that supplies the injectors) to reveal the pistons or plungers that might be stuck then apply a little TLC, lubrication and cranking to encourage them to dance again. If that works it would mean the pump is OK (maybe) and we would have gas at the injectors, which could introduce new problems,
It sounds reasonable enough, but is it the right path to take?

Also just a side note, the car will run as long as we supply it with ether.

The rack in the pump is gummed up.
Clean it up and then get the car running by jumpering 12v to the CSV .. that will keep it running enough to get the injector lines bled and the pistons in the pump flowing...
You can also take the return line off the rear of the pump and just put the key on and see if fuel is running through the pump.

I don't mean to hijack the thread, but what can I do if I don't have a cold start valve? My car is a ponton 220SE, and it has a momentary on toggle switch that someone added to move the rack to full rich for a cold start instead of a csv. Someone suggested that I use propane to get it started, but I am too chicken to try that.

Any replies would be most appreciated. Thanks.