I returned to the engine and once again cranked over the engine and no diesel atomised out of the injector, real head scratching time, I knew there was good pressure from the pump but why wasn’t it lifting the pintle? It must have been that the spring was too much pressure on the pintle so I backed off the top of the injector and sure enough diesel started to spray from the nozzle.
Have you tried a known good injector (outside the engine), to prove that there are no injector pump issues. You could for instance try the injector from your Petter AC engine, to prove this.
Should there be a spacing washer on the top of the LT injector?
This is unlikely to be a LT1 engine, as they were never fitted to dumper trucks.
As there are differences in injector styles. In order to help you further I need to know what Lister engine you have fitted, it could be a Lister SR1 or ST1 in which case the injector pump is enclosed within the engine, if it is a ST1 then two of the head stud nuts will be visible.
If it is a later dumper it will have a Lister flat top engine (Lister TS1 or TR1) these have high flange injector pumps and the top 1/2 of the injector pump sits outside the engine.
As it is I have backed off the top of the injector and there is a space between the body and the top of the injector
Sounds like you have a ST or SR1 engine, and your missing the locking nut that goes between the injector body and cap nut.
I put the injector back and tightened down the holding clamp and I now have White smoke emitting from the exhaust on flicking the compression lever, the engine hasn’t been started for years and I couldn’t get it to go, don’t shout at me but I think it may need a sniff of the old easy start to coax her into remembering what to do?
Nothing wrong with a spray of easy start when used in moderation (not unlike Alcoholic beverages), your engine may already have provision for oil injection (as others have said to raise the starting compression) the beauty of the oil injection plunger is that it delivers a known quantity of oil into the engine. If so it will be visible protruding from the cowling by the inlet port, if not you will see a rubber blanking grommet in the cowling.
One last item to bear in mind, these Lister engines are super sensitive to how far the injector tip protrudes into the combustion chamber, it is not unusual to find several sealing washers fitted between the cylinder head and injector, if so this can make handle start engines like yours a real PITA to start. I speak from personal experience.