I had a hard start issue last year. I changed glow plugs and batteries. That did not help. Then I removed the battery cables and installed new ones. the old ones showed no sign of corrosion, but I did it on the advise of someone I trust. That was the problem. Even thought the cables looked OK, they were indeed failing. The truck starts better now that it ever has. If I were you, I would also look into the battery cables. I got mine from powerstrokeshop.com because they had the best price around.