K jet, not holding pressure after switchoff

Hi
I did post this in the Fuel section but hope its ok to post here as well as it seems to get more trafficMy mk1 1.8 1983 GTI has been suffering from hot start issues. Runs fine, leave it 15 mins or so when hot , wont start churns and churns, if it does start runs rough till it clears its throat. leave it an hour or more to cool and starts fine.Ran the pressure tests (thanks for the Kit mr Quiff) All ok as far as I can tell, except pressure immediately plummets to 0 moment the ignition is turned off; as I understand it , it should hold a pressure for up to 20 minutesSo Ive had the fuel pressure regulator out, looks fine, green grommet looks fine , all clean moves freely.

Next suspect is the accumulator, but I want to be right as its a £170 part from VW H. My reading suggests there are no specific tests for it, anyone know differentOther suspect is the non return valve . the one next in line to the pump (is that the only one?)I recall having some issues with the valve which showed the exact same symptoms before when some prat (cant think who that was    ), refitted it the wrong way round. has worked fine since correction ten years ago. I havent touched it since.

What can go wrong with return valve and, is that more likely to have failed assuming it can, (or do I face I have stump up and change the accumulator).before I make any  expensive mistakes buying parts I dont need is there anything else I should look at that might cause this?Cheers in advanceLewis