Quick potted history:

- parked up about a week
- of and on -5 °C never got over freezing point, car never used
- started first time as usual - 800CCA / 75ah - Bosch

- ran for 5 minutes then stopped

Got a M8 round with a two battery Land Cruiser, 8 minutes at 2000RPM from him into my battery, it spun over like an airplane prop, no start - Aborted to the pub.

Next day ditto, it wouldn't start, pulled an injector pipe and it dribbled like a baby. Made good the injector and felt around for a hand primer, found it [after removing the plastic engine cover] flat as a *art, hand pumped and primed till the bubble was hard and the pipe was pressured. It turned over and started.

- ran for 5 minutes then stopped

Clearly the hand priming could pull all the way and fill the filter but the cars 12-17psi low pressure pump could not. Still not sure I've sorted it but the fact is a hand prime will do it so I figure [only a guess] the slack fuel filter was drawing in air allowing the fuel run back once the tension was off it. Took it for a 20 minute each way ride to here with my mate in tow in case I needed another pump~n~jump and it ran like a well tuned sports car. So I've been on a garage ramp and had a look all the way from tank to engine, no visual or otherwise obvious problems, didn't check the fuel heater, because the plastic cover was warm to the touch so I assumed working ok.

If that proves to be the case and its sorted fine, I'm happy. If not I'll 'chonk' about 4 inches out of the metal [coated] fuel line and stick an in-line one way filter, that'll stop the bugger running back and give me the added benefit of a 'visual' on fuel. Even without the - °C cold weather I'll know tomorrow if the fuel has 'run backwards'. Thanks for your attention on this joker2cv, I'm still open to ideas and suggestions from you or anyone else.

Update, and a salutary lesson. Went outside today, fired first time, so "a slack fuel filter was drawing in air" and allowing the fuel to run back was the cause. The lesson .. .. check the obvious first and the spin on fuel filter is the obvious.

So my Alarm going off sporadically, middle of night waking up the woodlands around, Looks like IPM, good, that's my answer and taken note.
all in all, true showing of what Corrosion on IPM terminals can do.