My 95 did the same thing when I had it and it was one of the glow plugs on that side. It had really high resistance. I replaced the glow plugs, harnesses and the valve cover. No more problems.The plug that goes into the valve cover had a melt down on my 96 f350 withe 300,000 miles. Before I go and replace the valve cover gasket and plug what else do I need to check that might have caused this problem?