I need to run past what i'm doing/working on. Its raining outside, i don't have a garage, the dog keeps barking, i'm tired, my fingers hurt. If you wouldn't mind reading what i'm doing and commenting on whether i'm going about this all wrong i'd appreciate any input 
my '89 F350 decided to switch modes of operation to "external combustion" (catch fire) at the lumber store while loading plywood, i had just started it perhaps 20 seconds prior and was loading lumber when i smelled burning-electronics smell. Popped the hood to find a minor oil fire and two bright-red glowing wires melting their way through the quick-disconnect coupling for the engine/glowplug wiring harness. Seems the connector had gotten a bit dingy and ohms law rules.. lots of current, some resistance, too many watts in a small area. But hey, at least know i know why it seemed like my glow plugs barely did anything for cold-starts in the past few months, poor thing.
Why anyone in their right mind knowingly designed it like this.. OK OK we've all heard this discussion before, so ill cut to the chase.
I've cut the two allegedly yellow (mine are crispy black) wires out of the glowplug harness, and disconnected an "orange+black" and yellow wire from the ignition-solenoid on the front passengers side fender. The rest of the glowplug harness is fine, and i have a spare GP harness from my last motor that threw a rod, so im all set there. I'm just in a mode of "lets not make the same mistake twice" regarding high-current protection. Resistance wire is a lousy idea in light of how inexpensive it is for me to put in a fuse. Lessons learned from multiple ford related fires. Fuse the GPs, fuse the alternator.
From studying pictures posted in other threads, ive determined "orange+black" is my glow-plug high current line, and the yellow line is +12v for the rest of the truck, lights etc (no lights, no ignition key, no nothing without that yellow wire connected).
Ive run, from my ignition-operated solenoid, a 12" 4AWG wire to a fuse block, with a 200A fuse. From here, 4AWG goes up along the old harness, to the glow-plug relay mounted on the top of the block. I've also run a new 4AWG ground wire, from the GP relay/controller, to the frame. The 200A fuse is a bit on the large size for the glow plugs, but in my testing with new glowplugs last year, the initial current draw peaked close to 150A cold and drops off down to 100-80A after 5+ seconds (once the plugs warm up, resistance goes up). my thinking here is if a glow plug shorts out or fails (mice!) i will hear bang sound from the fuse, rather than the truck catching on fire and burning out half its wiring harness. These fuses were $12 for a pack of 10. I'd rather endure dental work, than re-do this wiring harness again! Fuses it is
Where i begin to doubt myself is when i went to test this. I turn the key on (after reconnecting the yellow wire) and hear click...click-click-click-click. *sigh*. Its 45 degrees outside, so i'm going nowhere unless i fix this or plug in the block heater.
Current theory of mine :
bad glow plugs, plugs are 1yr old, perhaps a plug burned out / shorted internally and drew just enough current to smoke out my old wiring harness.
Unfounded concern of mine:
replacing the undersized crappy wires with heavy 4AWG wire is now happily feeding the plugs, perhaps the plugs draw a lot of current or the GP controller isn't functioning well without its former voltage drop?
I'm going to test every plug individually tonight with an ohm meter and variable PSU, i'm really hoping i just have a burned out plug or two, but i'm more concerned for the GP controllers "mystery of operation" -- is there any chance i have confused/upset its operation simply by ensuring it has a steady voltage supply with the heavier wiring? With the undersized wires before, there was some voltage drop from the battery to the GP relay/controller, at least 1v of drop (which is almost 10% change on a 12v system). If i get to a point where i can really find nothing apparently wrong, the idea that will surface back in my head is.. to give the GP controller a voice "oh wow the glow plug voltage comes up so fast now, hmm, must be a dead plug, im giving up! click click!"
I'll check each plug tonight, but any thoughts about the GP controller and my changes of heavier wiring -- i am curious! thanks
my '89 F350 decided to switch modes of operation to "external combustion" (catch fire) at the lumber store while loading plywood, i had just started it perhaps 20 seconds prior and was loading lumber when i smelled burning-electronics smell. Popped the hood to find a minor oil fire and two bright-red glowing wires melting their way through the quick-disconnect coupling for the engine/glowplug wiring harness. Seems the connector had gotten a bit dingy and ohms law rules.. lots of current, some resistance, too many watts in a small area. But hey, at least know i know why it seemed like my glow plugs barely did anything for cold-starts in the past few months, poor thing.
Why anyone in their right mind knowingly designed it like this.. OK OK we've all heard this discussion before, so ill cut to the chase.
I've cut the two allegedly yellow (mine are crispy black) wires out of the glowplug harness, and disconnected an "orange+black" and yellow wire from the ignition-solenoid on the front passengers side fender. The rest of the glowplug harness is fine, and i have a spare GP harness from my last motor that threw a rod, so im all set there. I'm just in a mode of "lets not make the same mistake twice" regarding high-current protection. Resistance wire is a lousy idea in light of how inexpensive it is for me to put in a fuse. Lessons learned from multiple ford related fires. Fuse the GPs, fuse the alternator.
From studying pictures posted in other threads, ive determined "orange+black" is my glow-plug high current line, and the yellow line is +12v for the rest of the truck, lights etc (no lights, no ignition key, no nothing without that yellow wire connected).
Ive run, from my ignition-operated solenoid, a 12" 4AWG wire to a fuse block, with a 200A fuse. From here, 4AWG goes up along the old harness, to the glow-plug relay mounted on the top of the block. I've also run a new 4AWG ground wire, from the GP relay/controller, to the frame. The 200A fuse is a bit on the large size for the glow plugs, but in my testing with new glowplugs last year, the initial current draw peaked close to 150A cold and drops off down to 100-80A after 5+ seconds (once the plugs warm up, resistance goes up). my thinking here is if a glow plug shorts out or fails (mice!) i will hear bang sound from the fuse, rather than the truck catching on fire and burning out half its wiring harness. These fuses were $12 for a pack of 10. I'd rather endure dental work, than re-do this wiring harness again! Fuses it is
Where i begin to doubt myself is when i went to test this. I turn the key on (after reconnecting the yellow wire) and hear click...click-click-click-click. *sigh*. Its 45 degrees outside, so i'm going nowhere unless i fix this or plug in the block heater.
Current theory of mine :
bad glow plugs, plugs are 1yr old, perhaps a plug burned out / shorted internally and drew just enough current to smoke out my old wiring harness.
Unfounded concern of mine:
replacing the undersized crappy wires with heavy 4AWG wire is now happily feeding the plugs, perhaps the plugs draw a lot of current or the GP controller isn't functioning well without its former voltage drop?
I'm going to test every plug individually tonight with an ohm meter and variable PSU, i'm really hoping i just have a burned out plug or two, but i'm more concerned for the GP controllers "mystery of operation" -- is there any chance i have confused/upset its operation simply by ensuring it has a steady voltage supply with the heavier wiring? With the undersized wires before, there was some voltage drop from the battery to the GP relay/controller, at least 1v of drop (which is almost 10% change on a 12v system). If i get to a point where i can really find nothing apparently wrong, the idea that will surface back in my head is.. to give the GP controller a voice "oh wow the glow plug voltage comes up so fast now, hmm, must be a dead plug, im giving up! click click!"
I'll check each plug tonight, but any thoughts about the GP controller and my changes of heavier wiring -- i am curious! thanks
