Hmmm.... This might be silly but I seem to remember you saying in another post that the car is parked on an inclined driveway?
if its low on fuel and the shape of the tank being the way it is, then no matter how much you try it wont start mate... Been there, done that, got the T shirt
Long embarrasing story:
My v6 broke down on bowes incline A1M as I was heading up it and I got stuck on the chevrons between two merging motorways! The fuel guage was on the warning light but showing just above the red marker! Being a time served mechanic and VOSA chief inspector, i automatically assumed it would be a mechanical issue... As you do!
I checked the cambelt, various relays and cut off switches, I even tried to fire her up with carb cleaner sprayed into the pre throttle body breather hose... No joy... I called a mate who had a can of fuel in his car and topped up the fuel... She still wouldnt start!
So... next logical process was..... Imobiliser, fuel pump gone or CPS. Then a memory of a conversation with my old mentor during my apprentice years popped into my mind "never assume things are complicated, always go for the most obvious, easiest solution first!"
So I sent my mate down to the fuel station to get another 5ltr can full. On his return I promplty chucked it in the tank and cranked the beast over... She started up after a couple of attempts and was no bother after that... Just goes to show how dumb a mechanical mind can be
If a 156 petrol or JTD is pretty low and /or ran out of fuel, then it takes at least two full 5ltr fuel cans to get the thing fired up again... If it's on an incline it will compound the problem
Failing that, remove the fuel related relay's in front of the battery, give the contacts (male and female) a damn good clean and refit.
Something tells me that the beasty will start up no bother though with the first option