The solution was quite simple as the piston of the stepper that goes to the spring is different in size from the each side, so you must be aware what side you are pushing it back to the distributor.
That was a suggestion that it can be a little more sense to have only one thread with all of the information inside instead of dozen more with the exactly same problem started all over again with no solution in the end but angry post from someone because exactly the same thing was happening before and before.
Sorry for disturbing, but I just saw you online and decided to ask for a quick tip rather than search. No need to be upset.
If you still want to know what was happening with my system I can tell that a sticking valve inside of the good for nothing necam vaporiser was at fault and needed replacing. The vaporiser can be changed to the
AT09 Tomasetto that is almost straight fit and better design and performance, rather than rebuilding necam distributor and changing a sticking valve all over again.
Stepper motors can be checked if they are operating by measuring it where it should be 50oMhs on two coils inside them.
Even if the bloody motor is dead it is obtuse to change it to another stepper motor even for yours 190 pounds. Because for less you can buy a set from stag that is a straight fit even for a necam vaporiser. Just unplug those injectors from distributor and put them in 4generation lpg injectors. Plug it in to the laptop (software is free) and synchronise it with the petrol injectors automatically.
All of that is written on those "moaned about" 60 pages
As classicswede said on one of his old posts "The best thing you can do is to change the front end"