This motor runs perfect once you get it started! the glow plugs are causing me hell,i screwed up and put AC 32g glow plugs in it a month ago then the solenoid went out.i replaced the solenoid it went out then i noticed on this site advising to use only motor craft glow plugs. well i went up to the local Ford dealership and bought motorcraft brand,then the fun began ....3 of the 8 AC plugs tips melted causing them to remain in the heads.. Tear down time now...well after yanking the top end off and re assembeling my 7.3 the glow plugs wouldnt heat ... solenoid failure again.so i created a bridge ( i think just like the solenoid is supposed to do when activted) and it melted the switch and wire in 5 seconds.i increased the wire size and put in a heaqvier rated switch it lasted 7 seconds ... i un plugged the glow plugs and could not duplicate this short.. i pluged in one plug at a time and every one appears to be a dead ground .. I am sure i am missing something real simple but i am lost....any ideas out would be greatly appreciated Thanks guys

 

Each of these glow plugs draws 19 A. Any switch you're putting in has to be able to carry that amount of current times eight. Without knowing how heavy your switch is, it's hard to tell if it's simply an underrated switch. You're correct about the AC glow plugs not being good plugs for the very same reason you're ripping your engine apart right now. I only ran Motorcraft in mine or maybe it was Bosch, I have to look. It would really be best to let the glow plug controller control the power to your glow plugs. Even the good glow plugs will distort after being left on too long. I think the Bosch or Motorcraft glow plugs will hold out about 40 seconds of continuous power, but don't hold me to that.

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I checked on the glow plugs, it was definitely Motorcraft, not Bosch.

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I have been running the same autolite glow plugs nkw for 5 years with out replacment of even 1 .... did my HG and they looked awesome .... wire wheeled them and used some anti-seize and tossed them back in ....

as for your issue it sounds like you may have a grounding issue with the GP relay .... check and clean all engine block grounds ....

 

thanks for the ideas i will go back thru the wiring..if i disconnect the glow plugs from the harness the dead short disappears.The draw increases with each glow plug i plug back in to the harness .This appeared after installing the Motorcraft ZD-9 f2tz-12a342-a glow plugs.i believe i am using the correct plugs.

 

What type of resistance is found at each plug? Have you pulled the plugs to verify their condition? Obviously the current required will increase with each glow plug thats plugged in, that is typically how electrical systems operate
The chance of having 8 bad glow plugs is quite rare, so in my opinion you should venture outside the box of bad glow plugs.
Its possible a connector was damaged and instead of making contact with the terminal made contact with the body. I would probably start by replacing the harnes and watching resistance to ground as I plugged each glow plug up. When you find a dead short you know the location of the fault.

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These glow plugs read 2 ohms, which is virtually a dead short. Your reading sounds about normal to me.

 

If his battery voltage was 12.6v and he pulls 19a wouldn't that equate to .66 ohm?

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Glad you mentioned that. To clarify, the glow plugs should be less than 2 ohms when checked. So yes, it could be .66 ohms. The voltage drops well below 12, though, so the actual resistance could be even less. At 9 volts, it would be .47 ohms. If a glow plug measures more than 2 ohms, it's supposed to be replaced.

 

I found it....... damn i feel like a fool but with out you guys help i would of had my first repair shop bill in 45 years ..i was stuck i let my experience bite me in the tail..Thanks for getting my head back to the basics the relay ground was faulty inside the box. it runs like it did day one!

 

kewl ..