Pierburg is complex.

The pulldown unit opens the closed choke flap a smidge when engine fires using vacuum akso, then electric and water heated bimetallic strip in autochoke gradually moves choke flap to fully vertical as coolant heats up.

I think the electric just overcomes inertia of flap when really cold, but that is a guess.

There's a part channel heater fuel passage to improve fuel atomization always on.

Theres an electric idle cutoff valve as discussed.

There's vac operated secondary barrel.

There's an enrichment tube.

There's a pump jet.

So, the carb base was definitely a problem. The car started and I managed to make a lap of the block. Sufficiently confident, I tried it again. The engine died completely after a few hundred yards. I made it back by squirting carb cleaner directly into the carb in runs of about 50 yards. I gather, there is no fuel going in at all. I added 5 litres to make sure the tank wasn't empty. I have already replaced the fuel pump and will check the vapour separator. A new one is arriving today. I had replaced it but broke one spout during one of the carb disassemblies. The old one was fine, the floats inside were free.

When rebuilding the carb I did not replace the float and needle but it seemed to move freely and the engine used to run fine before the car was parked for ten years.

I did not test the accelerator pump throughput. This may be a test of fuel making it to the carb reservoir. I did replace the gaskets, plunger, and cleaned quite a lot of ... that had accumulated over 40 years.

The saga continues.

Maybe perspective but the new base mount looks smaller.

Fuel strainer at inlet clear?

Idle circuit blown through?

When you say sedimentation filter do you mean the plastic swirl pot attached to carb?

It removes bubbles.

The carb well does too but swirl pot ensures even flow and slight reserve for low tank cornering.

The inline filter before the pump keeps out petrol station dirt (and fuel tank filler neck rust).

Is that plumbed right, because if not fuel likes to go down the return line to tank rather than into the carb.

Thanks dvderlm, yes, the vapour separator on the side of the carb. The interweb calls it different names, which adds to the confusion. Invariably, every time I re-mount the carb, I forget to catch the fuel hose under the bracket and have to loosen it again.

The new base is spot on, including a little indentation for a half flange of a tube that fits through the auxiliary aperture that I wasn't aware of. It's the funny perspective from the camera that give a false impression, I was trying to do "before" and "after".

I've cleaned the inlet filter mesh. I've dismantled and cleaned everything I could dismantle and clean. I think it's something quite catastrophic with the fuel access. I read something about fuel evaporation in hot engine and will check fuel gets. There may be gases trapped in the lines. What's irritating is that the car used to work beautifully before I SORN'ed it and now it's been truculent. I've changed ignition cap and rotor, spark looks fine. I'll change the vapour separator when the new one arrives, I struggle to see the fuel in the old one. The lines are connected correctly to the separator but it's some distance from the tank and I need to make sure fuel gets to the carb in sufficient quantities.