new motorcraft glow plug issues

6.9 with manual glow plug switch

so i had 8 autolights in my truck from when i bought it they worked amazing 50 degrees +/- 4 seconds of glow plugs shed start with less than a second of cranking time but i wanted to get those out in fear of the rumors i hear about the autolights

fast forward i installed 8 brand-new genuine motor craft glow plugs from o rilleys torques them to 12 foot pounds per manual then went to start it the next morning did my usual 4 seconds of glow and it cranked for 6 seconds before starting (same temp 50 ish) tried again next morning with 8 seconds about 4 seconds of cranking

still has the same power so i dont think i have a compression leak
checked that every glow plug is getting power so its not an harness/ relay issue to my knowledge
did i get some BOB glow plugs? if so how do i know i heard you can ohm them out but im not sure how thats done

thank you for reading any help, comments or tips is appreciated

That's crazy. What's the "autolite" glow plug rumor?

Jesus Freak said:

That's crazy. What's the "autolite" glow plug rumor?

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apparently the tips like to swell and break of in the precup

Long before I joined oil burners I read a review of some glow plugs, but I can't remember what they were. But in the review a guy mentioned that he had accidentally shut his truck down on WVO instead of switching back to diesel and he let the truck sit for a couple days before cranking it up again and HE SAID, " it smelled like someone burned down a McDonald's, but it fired right up". I don't think it was ZD9s or autolites, i seem to remember it started with a "G" but I don't know.

ohm setting in multimeter, negative lead on nut and positive on connector surface

hacked89 said:

ohm setting in multimeter, negative lead on nut and positive on connector surface

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well what am i looking for in the ohm reading? and nut as in the 3/8" for tightening the plug?

Yeah, test the resistance of the old and the new. For the autolites you took out you can test them with one lead on the connector end and one lead on the threads. For the motorcraft in the motor test them with one lead on the connector end and one lead on a good ground surface on the motor. A common rule of thumb is a good glow plug has a resistance of under 1 ohm, but really you probably want to see under a half ohm. If all the autolites test around 0.2 ohms but all the motorcrafts test around 0.4 or 0.5 ohms then that cumulative additional resistance across the 8 plugs would probably explain the extra time required on the new glow plugs.

Well folks what should I do

Austin86250 said:

Well folks what should I do

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I tell you what I'd do, I'd gather all the information and ask those who know on oil burners what they'd do...... so you're on the right track.

just went out on a limb and warrantied out 7 hope the new new ones work better

Damn. I'd be tempted to send them all back and use the old ones.

The key is the variance in resistance between the plugs, you want as little variance as possible. .5 ohm or under is great. But all the way up to 3ohm is within spec. It will just take longer. If all your plugs were .8 and .9 then it would be technically okay but not optimal. The variance between them is not okay. Let's hope the new plugs are consistent between each other.

Brian VT said:

Damn. I'd be tempted to send them all back and use the old ones.

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i feel the same way but I'm on a quest of a reliable truck and replacing pugs is on the list

hacked89 said:

The key is the variance in resistance between the plugs, you want as little variance as possible. .5 ohm or under is great. But all the way up to 3ohm is within spec. It will just take longer. If all your plugs were .8 and .9 then it would be technically okay but not optimal. The variance between them is not okay. Let's hope the new plugs are consistent between each other.

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i hope so too, i feel that is just unexpectable from buying motor crafts parts my old autolights where all .5 or .6

Well got some more today they are all .8 is that okay, I assume there better as they are consistent

That sounds about right.