[Laird Scooby]

I can see where you're going with that Ash, certainly a possibility. You forgot to mention to disconnect the field wire from the D terminal though while testing to prevent the alternator trying to charge thin air. For a couple of minutes test, it won't be a problem though, or at least shouldn't be.

Amorack - do you have a NOID light for testing injectors? If not, try and get one, they're fairly cheap and may reveal a fault if it takes that route.