injector/GP harness fried WHY
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Joined: May 2000
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From: wi
injector/GP harness fried WHY
i have not posted here in awhile but now i need help from the experts. i started up my 95 the other day after sitting for two weeks. ran fine for bout3-4 min then it all went bad, stated missing bad so i shut her down. got it in the garage and pulled the DS VC. found one bad Glow plug wire at the VC connector on the out side of the vc. i ordered the Valve cover kit from napa wich has two new connectors , gasket and inner harness both set of injector and gp, for 74 buck( great deal). put it on and tried to fire up, but no change, pulled the PS cover off and found two baddly fried wires in the plug. ordered annother set for tomorrow. but why did these burn up? is it the relay or the pcm causing the issue or freak occurance? this is the second time in five years this has happen. please help. jackk
Hotshot
Joined: Oct 2003
Posts: 17,799
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From: Ashland City, TN
Bad GPs' can cause the melting, or just a bad UVCH connection.
It's not the best system, but there isn't anything to change it to that is better as well.
I've always been curious as to why they really do burn up the way they do. seems silly.
But that piece of metal in there is thin enough where it can heat up enough with either it being a bad connection or passing of too much voltage to the GP's and causes it to burn up.
Ever used a paper clip with to much voltage though it while testing a circuit?
The paper clip burns up quick with to much voltage/amperage.
It's not the best system, but there isn't anything to change it to that is better as well.
I've always been curious as to why they really do burn up the way they do. seems silly.
But that piece of metal in there is thin enough where it can heat up enough with either it being a bad connection or passing of too much voltage to the GP's and causes it to burn up.
Ever used a paper clip with to much voltage though it while testing a circuit?
The paper clip burns up quick with to much voltage/amperage.
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Senior User
Joined: May 2000
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From: wi
id there any way to check the glow plugs? the ones i pulled out where the harness was bad look great. hook them up to 12v and turned red in like 3 seconds. they are about 4 years old. i am just hoping there is nothing ore wrong , guess i should replace the relay also? only 4 years old also. thansk for the reply. jackk
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Joined: Aug 2006
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From Racer X :
Excess resistance in the circuit is what causes it to burn the harness. Wiring is to small to handle the heat when the plug doesn't use the amps up to heat the tip. Heres a simple explanation:
Ford/Nav VC gasket/harness was redesigned with better conductors several years ago. Here's a basic way to explain it without math at all:
If the glow plug (load) were to short, the burn or weld will happen at the point the short occurs. If you use a welder it welds at the electrode (load). It won't burn up your weld cables.
So why does the harness connector melt? Excessive Resistance causes heat. A GP has little resistance or ohms. It's nearly full power that warms the tip using up power to make heat. What little power isn't used returns thru ground to battery completing the circuit. Excess resistance or poor conduction from green stuff or corrosion prevents full power from flowing to the load (glow plug). The wiring gets hot and melts because you still have a complete circuit back to battery ground, but no load to use the power up and keep the wiring cool as power flows thru it.
Now think of the welder again. What happens if you forget to put a ground clamp on the metal to be welded and touch the electrode (load) to the metal? Nothing. The circuit is not complete, so no power flows at all. No weld or short.
Best way to prevent the burned wiring is a good conductor to your GP's. I pack Di grease in all underhood connectors. The best way to keep the connection moisture free and clean is silicone dielectric.
If your harness burn't from the GP connector back, then you may have a shorted plug. Ohm it, compared to the others. If it ohms out higher than the rest it's also BAD. The extra resistance is inside the plug, not allowing full power to the tip.
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Ford/Nav VC gasket/harness was redesigned with better conductors several years ago. Here's a basic way to explain it without math at all:
If the glow plug (load) were to short, the burn or weld will happen at the point the short occurs. If you use a welder it welds at the electrode (load). It won't burn up your weld cables.
So why does the harness connector melt? Excessive Resistance causes heat. A GP has little resistance or ohms. It's nearly full power that warms the tip using up power to make heat. What little power isn't used returns thru ground to battery completing the circuit. Excess resistance or poor conduction from green stuff or corrosion prevents full power from flowing to the load (glow plug). The wiring gets hot and melts because you still have a complete circuit back to battery ground, but no load to use the power up and keep the wiring cool as power flows thru it.
Now think of the welder again. What happens if you forget to put a ground clamp on the metal to be welded and touch the electrode (load) to the metal? Nothing. The circuit is not complete, so no power flows at all. No weld or short.
Best way to prevent the burned wiring is a good conductor to your GP's. I pack Di grease in all underhood connectors. The best way to keep the connection moisture free and clean is silicone dielectric.
If your harness burn't from the GP connector back, then you may have a shorted plug. Ohm it, compared to the others. If it ohms out higher than the rest it's also BAD. The extra resistance is inside the plug, not allowing full power to the tip.
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Hotshot
Joined: Oct 2003
Posts: 17,799
Likes: 100
From: Ashland City, TN
Except make sure you use conductive grease, not dielectric grease like he did.
Dielectric grease is not a conductor.
And its good too that they burn up.
cause it acts like a fuse, otherwise you might be tapping those GPs out if they decided to release into the head and weld themselves in.
Dielectric grease is not a conductor.
And its good too that they burn up.
cause it acts like a fuse, otherwise you might be tapping those GPs out if they decided to release into the head and weld themselves in.
Elder User
Joined: Aug 2009
Posts: 869
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From: Michigan
Except make sure you use conductive grease, not dielectric grease like he did.
Dielectric grease is not a conductor.
And its good too that they burn up.
cause it acts like a fuse, otherwise you might be tapping those GPs out if they decided to release into the head and weld themselves in.
Dielectric grease is not a conductor.
And its good too that they burn up.
cause it acts like a fuse, otherwise you might be tapping those GPs out if they decided to release into the head and weld themselves in.
Elder User
Joined: Aug 2009
Posts: 869
Likes: 1
From: Michigan
william are you talking about the connection from the uvch to the actual GP? and not the harness to gasket connector right?
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Postmaster
Joined: Sep 2007
Posts: 4,195
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From: Medford Oregon
Except make sure you use conductive grease, not dielectric grease like he did.
Dielectric grease is not a conductor.
And its good too that they burn up.
cause it acts like a fuse, otherwise you might be tapping those GPs out if they decided to release into the head and weld themselves in.
Dielectric grease is not a conductor.
And its good too that they burn up.
cause it acts like a fuse, otherwise you might be tapping those GPs out if they decided to release into the head and weld themselves in.
Where in the world did you come up with this. I've read it 3 times and can't make any sense out of it. Actually, no .. I'm not even going to try. Your thought process is weird.
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FOREIGN GURU
Joined: Jul 2006
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From: Celaya, Gto. MX
Except make sure you use conductive grease, not dielectric grease like he did.
Dielectric grease is not a conductor.
And its good too that they burn up.
cause it acts like a fuse, otherwise you might be tapping those GPs out if they decided to release into the head and weld themselves in.
Dielectric grease is not a conductor.
And its good too that they burn up.
cause it acts like a fuse, otherwise you might be tapping those GPs out if they decided to release into the head and weld themselves in.
https://www.ford-trucks.com/forums/1...ml#post9852112
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