[Vwdiesel] An off-topic, but Diesel question

[Shalyn Shourds]

Sorry for the lack of VW content, but I don't know a better group of Diesel mechanics.  Brother-in-law has a 92 Ford 250, about a quarter million on the clock.  He finally got around to changing the glow plugs after a couple years of ether starts.  Now it starts fine cold.  It, however, won't start if he warms it up then lets it sit for an hour turned off.  I didn't know what to tell him because if it starts cold, everything mechanical should be working.  My only thought was that maybe the glow plug coolant temp sensor was saying "don't glow" erroneously when it was a little warm, but not warm enough to start unaided.  I know very little about those engines, though.

Thanks in advance,

-Shalyn