Try removing regulator from hp pump and checking the condition of the fuel in the back of the pump then wipe out with a rag and blow out the back of the pump and regulator with an air line and then try it again as I appear to becoming across this type of fault quite reguar. If this does work you have an issue with contaminated fuel and it is not a perminent fix it just confirms the problem I have had these cure the problem for long periods of time and short periods
hth
carl