My BMC 1.5 will only start if I first loosen the upper injector pump bleed screw, the one above the idling damper adjusting screw. I have to loosen it enough to let a little fountain of fuel come out while cranking, and then it will start immediately, even with no glow plug preheat.
It started doing this after cleaning the injector pump filter gauze and replacing the fuel line. At first I could not start it, no matter how much fuel I bled from the system. If anything, it seemed like not enough fuel was coming out of the injector pipes when cranking the engine. Out of frustration, I thought that maybe there was air trapped in the injection pump that required cranking to get out. So I slackened the upper bleed screw and started to crank the cold (no preheat) engine. It started immediately! I tightened the bleed screw, broke the head of the screw off, observed a pretty little fountain of diesel (not unlike that from a male infant letting it go while getting his diaper changed), stopped the engine, and cleaned up some of the fuel mess.
I removed the idling damper locknut and screw, extracted the broken bleed screw, and replaced it with one I made (I'm in Canada, none to be found anywhere here, and Calcutt doesn't ship across the big pond). Cleaned everything thoroughly, reassembled, and am able to repeat the odd starting procedure every time. After the engine starts and I (gently) close the bleed screw, the engine keeps running for at least a minute or two. I stopped it intentionally a few times, and other times it reduced rpm and stopped on its own. But it would always restart right away with my newly patented crank-bleed-start procedure. When the engine is running, the idle rpm is too high, maybe 1500 to 2000, and it varies each time I start the engine. The throttle response is also really slow, so I believe the idling damper is out of adjustment. But what could require bleeding in order to start?