Just a thought hear im wondering if there is a intermitant fault on the operation of the 5th injector.....causing no start from cold sometimes...do check the 2 terminal plug on the Brown Timer...pull it off...look carefully to the Brown and White / tracer wire terminal...has.is it opened up over years ..or dirty..these plugs tend to fall apart with the position there in right at the back of engine...its the Brown & White only you need to look at......this is in fact the "negative" for the 5th injector....the valve on the Fuel Pump only keeps some pressure in the Fuel line from pressure regulator to pump after engine turned off. Peter