Realy Strange Starting Problem !! HELP!!!

Hi Guys. I have a 1994 super custom 3L Turbo Diesel automatic 4x4. Been driving it for 5 years and runs like an absolute dream.
HOWEVER: Since a few weeks ago, after the vehicle has stood for like 24 hours and I turn the key, it starts absolutely perfectly and hums like a dream: smooth, no misses, no hunting, no irregularities at all. THEN, after about 40 secs or a minute or so, it dies like it was shut off. No misses, no farts - like someone simply turned off the ignition. When I then again turn the key, it starts, runs normal for 2 to about 6 secs the dies again. This keeps on for around 12 to 15 attempts before it keeps running continuosly and absolutely normal again.
This happens everyday - not particular to morning or day, as long as it has stood for like 20 - 24 hrs. First time it fires it runs instantly after a mere one crank of the starter (has always done) then dies after 40 secs or so and the issue then repeats as above. Once it has sustained running after 15 attempts or so, you can drive like 100 miles without any further problems. Until it again stands for a long time.
Have checked water in the fuel and air locks in the fuel: no probs there that I can see..
What now? Cannot take it to a Toyota dealer here (South Africa) as they refuse to work on it as it is an import ex Japan and not an available model in the country.
Desperate as I am now wearing out the starter...
This vehicle has given me 160 000km of absolutely faultless driving and the engine runs like a sewing machine. It gas always started instantly and idles smoothly and steadily even in ice cold weather. Now it has this cut-out prob when having stood. Please note : even with this problem, when it stars and even on the few second runs when starting, it idles absolutely smoothly. Also when it first starts and runs for like 40 secs one can depress the accelerator and run at like 3000 RPM or so: it still cuts out after 40 secs or so. It seems that it gets a signal to shut down from somes sensor?
Any help will be appreciated.
Dane

Damn, thats a curly one.. We have a bit of the same problem in Aus with Toyota dealers. I think that it is mainly that they don't know anything about them. If you really push the issue they will look. Can you get anyone to check the OBD to get faults for you? If not there is a list of faults and how to find them manually here somewhere. Here it is. Hope you find something mate
https://hiace-super-custom.forumotion.com/t439-engine-managment-fault-codes-and-how-to-read-them?highlight=fault+chart

I'd look for a fuel line air leak, maybe draining back to the tank after standing, once started on a full filter sucks up the air and stalls?

Try the primer pump before and after the initial start, it should be no different. It is also possible that the primer diaphragm has a pin hole in it and sucks air?

I would try a litre of clean diesel direct to the pump to rule out fuelling issues. Then the ECU and connections if it persists.

Long story short: Replaced the ECU with new one and she's like new!! Cost of unit? US$ 1100.00 from Toyota....

Ouch when I needed and ECU it was £900, gave up and sold it on - ever had a kick self moment!

I'd have to have a think about spending that much....

Or you could have opened up the ECU box and replaced the 2 or 3 capacitors that were faulty for something closer to AU$10.00.
All that is needed is some basic soldering knowledge and to know which capacitors to replace.
I've seen and heard of this problem so many times.........I am so glad that my vehicle does not have an ECU. (Or anything else electronic for that matter, save for the speedometer sender)