I had the same problem....Auctually mine would not start at all if I didn't plug it in...I was ready to pull the glow plugs...Then I put it on a scan tool...My oil temperature sender was bad.... It tells the glow plugs to turn on... It screws on the top front side of your engine...It ran me like $50.00 at ford...Advanced auto, Autozone and Pepboys didn't know what the stinkin thing was....that wasn't a big surprise.....Nappa had one in stock but the one they had was not the same one that was on my truck...I even checked it in other Nappa's they were all the same and they even showed me what it looked like in the Nappa book and it was the same they gave me, so going to nappa is a waste of time. If you find it anywhere stress to them that it is and OIL, NOT A COOLANT sender because people were giving me prices for them instead, it saves you a waste of trip.