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'91 F-350 electrical problems.

4K views 16 replies 6 participants last post by  drinkypoo 
#1 ·
Hello I am the proud new owner of a 1991 F-350 7.3L with a turbo. It's a basket case; but it's mine so it's time to repair it.


I recently went out to start it up and the battery was dead so I assume the alternator is out. I attempt to jump start the truck with my honda and notice that when I try to turn the engine over some wires in the engine bay begin to smoke (this is after waiting for the glow plugs to warm). I stopped attempting to jump the truck for fear of further damaging it.

I can't seem to figure where these wires go and I was hoping you guys could tell me and maybe help me stop it from happening.

I have some photos of the wire harness in the area around the smoking wires.

Imageshack - img2759u.jpg This is the location of the connector on the passenger side of the vehicle. The connection with the yellow wires is the one that was smoking and I suspect it was the yellow wires.

ImageShack® - Online Photo and Video Hosting this is a close up of the connection mostly focused on the side of the connection closer to the engine block smoke seemed to be coming out of the section that is covered by the wire guard thing.

ImageShack® - Online Photo and Video Hosting This is a close up of the fender side of the connection

ImageShack® - Online Photo and Video Hosting this image is of where the wire leads. It goes over the passenger side head and splits there going to the front and back of the engine going out of site.



Should I attempt to charge the battery(s) with a trickle charger over night? Which battery?

Any help identifying these wires or any components these wires lead to would be greatly appreciated.

Thanks!
 
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#2 ·
Those are the leads for your GP harness. If I had to venture a guess I would say that your GPs are toast, did this truck have the original glowplug setup or is there a push button bypass in the cab?
 
#3 · (Edited)
1st pic is the connector that has a tendency to burn up......so take the effected yellow wires, cut and splice them individually outside the plug. Leave the rest of the wires in the plug as is.

Disconnect batteries before doing anything......

Check my pics under my name....... lots of info there.

http://photos.thedieselstop.com/showphoto.php/photo/34664/ppuser/28329
 
#4 ·
be sure to connect to the correct battery. Look in your manual. I cant remember but I think it tells you not to connect to the driver side battery when jumping it. but dont quote me :)
 
#5 ·
That's correct, because the cables run from D/S to P/S to starter. However, they're 00 cables, and your jumpers are probably what, 8ga? 6ga at best if you got the nice ones?
 
#6 ·
So, after I get some new glow plugs, splice those two wires together and buy a new alternator it should be safe to jump?


Thank you all for the information so far, I'm sure I'll be here a lot. I need to get this bad-boy into shape, and there's much to be done.
 
#7 ·
Remember only GPs are Motorcraft or IH no others >>>>>>>>>>> search the net.

I would charge it overnite at least........if you think jump starting with a Honda will replace 2 X 850CCA batteries fully charged. What your smoking is NOT legal.
 
#8 · (Edited)
What do you mean the glow plugs are Motorcraft or IH? Are those the manufacturers? [edit] a quick search cleared that up. Yes, they are.[/edit]

Also, should I (when I splice the wires together) cut back the wire coupling to the block and see if the yellow glow plug wire insulation is intact? The reason I'm curious is because the insulation looked like it wasn't too damaged outside of the wire coupling. Could the rest of the wire be melted inside of the coupling?

And I see what you mean about the jump starting with the honda, it's a little starved on power for getting that much compression.
 
#9 ·
Some PO melted MY yellow wires, and spliced them. I'd check for resistance and if it's not 0 or damn close, I'd check them.
 
#10 ·
Once you cut 1 Yellow wire ""AWAY FROM" the plug connector at both ends, connect the two new wire ends together with solder and heat shrink tube material. Do the same for the the other wire........

You could use a non plastic coated crimp joiner and solder the wires into it.... then use heat shrink tube to cover it.

You could pull the connector apart and check for damage to other wires if you wish...
 
#11 ·
I just installed a new alternator and I spliced the two glow plug wires together around the plug. I had been charing the batteries with a trickle charger both batteries are at 11.7 volts. When I crank the engine over a couple of times (after letting the "wait to start" light turn off) I don't get any firing in the cylinders.

What do you guys think? Is there anything I can add to the fuel air mix to help get the fuel to burn at a lower temperature? I know with gasoline engines one can just spray some starter fluid in the air intake and you've usually got some igniting fuel. Can
I use that with a turbo or even on a diesel engine? Do you think I need to replace the GPs as well as connect those GP control wires?
 
#12 ·
A fully charged battery is 12.6 volts. Until you have two batteries in the truck both capable of holding 12.6 volts, you're going to have problems.

You can spray ether but only if you disable the glow system. You can pull a relay, I forget which.
 
#13 ·
A fully charged battery is 12.6 volts.
True, when voltage stays at 12.6 without a charger connected. With a charger connected, wait until the current drops close to zero. Voltage should read somewhere between 13-14, depending on the type of charger. If the OP's batteries are only reading 11.7 volts they've got a long way to go. Don't use anything smaller than a 10 amp charger. Trickle chargers/maintainers are for keeping a fully-charged battery topped off. They are too small to recover a pair of depleted truck batteries in a reasonable time frame.
 
#16 ·
With two new batteries it came to life! it fires up well now and runs strong too.

I was curious how how much boost should I be receiving out of my turbo? While driving down the road I get about 1 psi; when accelerating I rarely get above 3 or 3.5 psi. Is that normal?
 
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