Yesterday the wait to start light dident stay on long. So when I went to start it it died wright away did it again the second time but the light dident even come on. The third time it started but rough running. But today it worked just fine have a 2002 cummins with 71,000 miles on it. The outside temp was in the low 40's

 

Try cleaning and testing your IAT sensor... This controls the Grid heat and fueling of the truck in cold temps...



For more information go to...
http://www.frontiernet.net/~mopar1973man/iat_sensor.htm

 

The more glow plugs that are not working the shorter the light stays on. Sounds like you need to check your glow plugs, but at only 71,000 miles that seems odd.

 

Comedy right?? We don't have glow plugs...

 

No Kidding... This isn't a Ford or Chevy! This is a Cummins they have grid heaters! Kind of like a toaster...

The only thing that controls the length of time is the temp that the IAT sensor sees in the intake... The hotter the temp in the intake the shorter... Or the colder the temp in the intake the longer it will heat... So this points to checking the IAT sensor for fouling and for proper OHM reading for temp. Which I posted the link to my page on how to do...

Yes IAT sensor can fail without tripping a code or lighting the CEL light. They can get to the point that they don't show cold temps or visa versa...

Read this... Really good infomation on IAT testing...
http://www.smokindiesel.com/Technical.htm