My truck never gave me a problem up until about a year ago (99 diesel) and then it became hard to start. I should say it always started, but not until I'd cranked it a while. Took it to a diesel mechanic and all he could do was put a light on the dash to indicate to me if there was any fuel in the system. Said it was what cummins recommended. It gets better when it's warm. But 5 minutes in the parking lot it starts again. Any ideas?