I'd de-armoured it (it came from a keypad model as best as I can remember) around September last year. I'd not really tried to check it in other ways as it appeared to be full of fuel (the inlet / return were cut and plugged and I could see fuel in them)
Worried about it standing too long and the fuel (and who knows what else water etc) could be in it, I wanted to test it. The delivery pipes were very rusty although they were sufficient to face well away from me and to test it.
Thing is (and the question really) I did not have anything immediately suitable to test it with, I recall Jim saying LHM is a good thing to use, I'd not want to use derv as that's a bit dangerous I think.
I had some Dex3 ATF so I used that. Initially I left the solenoid closed and the inlet in a fresh pot of ATF and the outlet into an empty tub. After some turning it appeared at the outlet so I whipped the plunger / spring out and popped the solenoid back to save messing with a 12v supply. More turning and I could see signs of leakage from the delivery pipes, so after watching closely I saw it did appear from all of them.
Question is: Is ATF OK to use for 'testing' and perhaps 'storage' ? , naturally I'd ensure it was fully swilled out with derv before (if) fitting. I'm thinking it may be better standing with ATF in it than ancient derv, what little did come out did not look very good, I think it was actually about empty anyway.
Slightly concerned it may not work properly as I don't have any method (besides fitting it!) to confirm its really working, internally it is taking fuel in and returning it and there is some outlet at the delivery pipes in sequence as best as I can tell.