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gettin there
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Discussion Starter #1
Installed all new zd-9s and connectors to them. Before I turned the van on I turned the key to see if WTS light stayed on longer which now it did. Before it only stayed on for 5 seconds. 2 of the wires to the plugs were actually severed. So now it stayed on for 15 seconds or so. I wanted to switch out the GPR to the stancor before I put doghouse on and wrapped it up. My idiot self didn’t see the importance of the plastic pedestal underneath the the GPR so I tried to bypass it and hooked wires directly to stancor. I got WTS light for maybe 3 seconds max and wouldn’t start so I knew something was wrong. Hooked the old one back up and nothing. I figured I fried the controller so I bought a new motorcraft one for $130 and now it’s still has same symptoms. I tested voltage on the hot lead and it read normal but I’m not reading anything on other studs even when key is turned. Did I short something else that’s interfering with the connection? I don’t think there’s any fuses responsible? I can’t see how the brand new GPR is faulty but acting the same as the old one.
 

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Check the resistance of each of your glow plugs. You may have fried them again. The 6.9 diesel used 6 volt plugs. If you bypassed the old controller then you accidentally put 12 volts to the 6 volt glow plugs which causes them to go poof very fast. There is a wavy looking piece of metal on the old controller that is really a resistor. The resistor drops the voltage so that the glow plugs only see 6 volts.

Cj
 

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gettin there
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69 Posts
Discussion Starter #3
Check the resistance of each of your glow plugs. You may have fried them again. The 6.9 diesel used 6 volt plugs. If you bypassed the old controller then you accidentally put 12 volts to the 6 volt glow plugs which causes them to go poof very fast. There is a wavy looking piece of metal on the old controller that is really a resistor. The resistor drops the voltage so that the glow plugs only see 6 volts.

Cj
Check the resistance of each of your glow plugs. You may have fried them again. The 6.9 diesel used 6 volt plugs. If you bypassed the old controller then you accidentally put 12 volts to the 6 volt glow plugs which causes them to go poof very fast. There is a wavy looking piece of metal on the old controller that is really a resistor. The resistor drops the voltage so that the glow plugs only see 6 volts.

Cj
man I’m gonna be pissed if that’s what happened. But shouldn’t I be reading some voltage on another stud on top of relay if the controller was working? Or the fact that the plugs are done are they telling the controller not to relay power to the other stud?
 

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It could be that the controller gets its ground through the plugs... Check them first and make sure they are still ok... It has been a looong while since I have been under the hood of my old 6.9 (currently rusting away in my folks field).

Cj
 

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Does the GPR have power coming in?
 

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gettin there
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Discussion Starter #6
Yes it has power coming in. But that stud is the only one reading any voltage. Even when the key is turned. I can check the plugs tomorrow. I’ll be bummed if I ruined them all. At least I’ll get to return the expensive controller
 

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I seem to recall that the controller works partly on the resistance of the glow plugs. As they heat up the resistance changes and the controller senses this in order to cycle the plugs on and off. But don't quote me... I understand your frustration... The 6 volt plugs are a real pain. Once you lose one the resistance changes for the rest and they see a slightly higher voltage which in turn burns the next one out that much quicker... repeat a time or two and the last ones go really fast.
 

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There is also a ground from the relay to the motor on those. Mine broke years ago, had the same issues. I also did fry all the glow plugs. For some reason, my truck eats the relays,
So I keep a spare Napa one in the glovebox. Gets me out of trouble. I’m hunting for the wait to start module, but no luck yet. I wait for the relay to click a few times and go. I also used a 04 6 liter harness for mine after shopping around for the bullet connectors that nobody in my town has for some reason. Helped a lot with the connection issues
 
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