It's that time of year again where I get time to work on this engine.
I've got the thing running so here's an update for all who might be interested.
I've been installing the pump with the control lever in the wrong position.
As you may know, there is a fork that moves from side to side to control the injector pump. I thought I had it in the correct position within the fork, but on further inspection I had it in the wrong position.
The picture below shows where it should located (7) but maybe because my engine is for a generator with a set RPM, I am presented with the gap next to it (with the red line). To see position (7) I have to manually move the stop lever to the stop position to see it.
with the lever in the red line position, it allows a small amount of diesel through but not enough to run, this explains why it would fire for a second then cut out
Although it's very frustrating and I'm angry with myself for not noticing such a stupid thing, I'm glad that it's working now.
Thank you all who have helped out.