You have a problem with the lift pump
It's the lift pump.
OK, so the lift pump piston should be producing more pressure.

Which kit did you use to rebuild the lift pump?
I bought individual parts from the Dealer, so the hand pump, valves, o-rings, spring are new. The piston is the original.

If you didn't use an IP lock when you stuck it in, it could have moved out of the place you set it at as you slid it in.
This never occurred to me. When turning the inj pump on the bench it has 'indent positions' where it would not rotate easily off this posn - and the two-marks-line-up occurs in one of these stable positions. So this is possible but not likely I think.

What is the history of the engine?
It was almost certainly neglected, judging by the rest of the car. It had 180k miles, professionally turbo charged from new which was pretty common in this market. I did have it all apart and new liners/pistons/timing chain etc, rebuilt head. I did nothing with the timing device/ vac pump.

As I said, the car was running OK until recently, when it stumbled and died.

replace the cigar hose with a temporary clear pvc tubing
Testing the lift pump
Thanks, I will do that.

IP timing
Turning engine clockwise looking from the front to 24BTDC with the number 1 cyl cam lobes pointing upwards-ish, inj pump installed with its marks in alignment.
set the engine to TDC on #1 on the compression stroke, set the IP correctly, and install. AKAIK this should be at 24BTDC??

Thanks