RE: Re: RE: 2nd daft 816 question
Martin, that shut off tap just before the injector is not what you think it is. The fuel hand starting pump is also a priming pump for clearing air out of the fuel system. That tap is the high point in the system and you pump the handle to get fuel out of that point. If it's closed it does NOT shut off the fuel going to the flame heater nozzle.
And the more I think about it (and look at the -20 and -20P manuals), the more I think that that gauge should not show pressure unless you're pumping on it. I think the source of fuel for that pump is before the Injector pump's pressure side which should mean it's NOT going to see pressure from the engine running. Which makes me think you have a faulty gauge or something else going on.
First thing to check is to see if you have fuel spraying. Crack that valve with a bucket under it while the engine is running it should NOT spray with any pressure OR you can pull the spray nozzle and see if it sprays or dribbles fuel while the engine is running. If it does it either needs to be cleaned or likely replaced.