That rings a bell! I have same trouble with mine. J Plate (120,000 miles)with a Lucas CAV pump. I am by no means a technical expert with cars, but this is my experience. About a month ago I purchased a new stop solenoid (£20 something), had it fitted and this cured the problem... Mechanic then went for a drive in it to a shop and when he got back in it would not start! Fitted the old stop solenoid back on and all has been well up until today. Verdict was that there must have been some muck in there. So you could try removing and cleaning (not sure of the correct process). May have a go at fitting the new one back on tomorrow, (this sould only take a few minutes on the Lucas CAV). Another consideration is that the new solenoid i bought was a dud, although the mechanic tested it (connect to spare battery), and it was working on the bench. I've probably been unlucky with mine, Should be a simple fix and is not uncommen. Hope this helps.
Paul
September 2008
howtomendit.com for free repair help, information and advice.
