mass glow plug failure???

[troupp]

What would cause 5 of 8 to fail within a month of all being checked good?
none were swelled, but all had whitish buildup on them along with some soot.
The truck generally smokes a little(black, under load) but doesn't smoke excessively, like some I've seen, hasn't ever had the timing checked, but it starts good, and does not rattle excessive. Any thoughts? thanks

 

[sassyrel]

well--are they ford berus?????----if so--may have got some defective ones--replace with new ones--and if still does it--controller is heading south--or not grounded right--and keeping them on tooooo long-----

 

[Mr_Roboto]

A bad controller ground will keep the plugs on too long. The controller grounds to the rear intake stud.

 

[troupp]

four were lucas, and 1 was a delphi, and I have no idea who installed the mix and match set in it as it was the donor motor. Ground seems good after replacing the bad ones, it seems as though it cycles them on for about 11-12 seconds first start in the morning, and for about 8 seconds at night before I leave work, as it is warmer when I leave work.