i have an 86 6.9 the engine came from another 86 6.9 i was told this engine before was known to burn up plugs and i put a bran new set of motorcraft bureu zd1's and they are only about 1 1/2 months old and they are on a push button and i have only cycled them a couple times right after startup to clear the white smoke... i let the truck sit for around 3 or 4 days and went to start it and i suddenly had no glow plugs... my wait to start light still comes on while pushing the button but i don't have any glow plugs... and i hate ether! i feel like im chasing my tail and cant catch it with this truck lol

 

Did you verify that you are getting juice to the plugs. Next thing is how large is the wires going to the plugs. Ford used the two heavy wires then split them down to each plug with a smaller gauge wire. This may be to restrict the voltage to the plugs some. IDK for sure but just an idea.

 

Yes the wire is to drop the voltage, IIRC its a 200amp draw on a 10ga wire that drops the voltage to 7.5 or somethingclose to that. And the wires going to the plugs are fuseable link. So check for voltage at the terminals that attach to the plugs and do a quick test on the plugs by hooking a testlight to the + side of the batt and touching the spade on the plug, if it lights the plug is good.

 

did a quick check today and the 3 plugs i checked are no good... but it seems like it was a sudden burnout not like it got harder and harder to start it was all the sudden and my push button is hooked up by pos. wire to the button and wire from the button to the glowplug relay and i can hear it click when i push the button and like i stated i checked 3 of them today and the three i checked are bad...

 

Make sure you have power to all terminals, otherwise voltage to the rest is increased.

 

and if the relay sticks it will smoke the plugs.

 

Maybe a few popped off I will have to check but I could tell when they were on and when they were off because the lights in the cab would dim with them on