All 8 Glow Plugs on my 1986 Ford 6.9 Diesel Pickup fowled out at the same time while driving just a few minutes after starting vehicle cold. All Glow Plugs tested good just prior to this happening. Glow Plug controller checks out OK. Injector pump was in need of repair prior to this happening and has now been rebuilt. What would cause a current spike that would make all 8 glow plugs to burn out all at the same time?

 

I can only think the glow plug relay did not cycle properly. This would make the glow plugs operate on full 12 volts without a break. What I can recall is they are a 6 volt plug operating in a 12 volt environment. If the power does not cycle (off and on) they will burn out. Also, there may be a short in the wiring for the glow plugs. I cant think of any other way to cause them to short out like that. Unless, someone used either to start the engine and you are lucky the heads didnt get blown off.