I got a call from my brother yesterday. The glow plug wires caught fire and burned when my farm truck was started. Truck is a 1992 F-350 7.3 non-turbo stake body dump. I knew there was a problem, but hadn't gotten to the farm to fix it. He put the fire out before it destroyed the truck, but a mechanic friend that saw the damage said i should bring a new harness "from the fuse box on the fire wall to the glow plugs".

I've taken the time to read many of the old posts about my same problem, and understand I may need a bunch of new stuff, and it may well run me over $300.00 in parts alone.

This is a farm truck that gets driven under 1000 miles/year, and rerely leaves the farm.

I read one fellow's post saying you could use regular wire and fusible link to make a new harness.

My neighbor suggests using a momentary switch instead of the timer that likely caused the problem in the first place.

I'd like to hear you folks thoughts. Should I just take some wire and rebuild it farmer style, or am I asking for big problems?

Thought about upgrading my insurance to full coverage...............

What would be a fair price to pay from the bone yard for "from the fusebox on the firewall to the glow plugs"?

Thanks,

Beagledog

 

I guess whether you replace the whole harness or repair depends on how much damage there is. if it was only the glow-plug circuit and you could salvage the harness from the glow-plugs to the controller I would fix it...seeing as it isn't used too much I think that repairing what you have is a good idea as long as the repair is easier and cheaper than replacing the harness.
I had a small short in my truck ( at the large engine connector) and I just repaired what was damaged...

good luck'
Corey

 

You need to use a relay in the glow plug circuit, 192 amps draw while heating the glow plugs.

The glow plug circuit does not go toward the firewall, it goes to the passenger side battery.

I don't know how comfortable you are with wiring and how much damage is done, but the IDI wiring is not that complex.

We can talk you through it I am sure.

 

Thanks for the replies Dave and GoodBoy. Doesn't go to the firewall eh? Maybe that's why the mechanic who looked at it is unemployed?

I'm going to try a couple more boneyards, to see if they have the whole kit-n-kabootle. Any idea which years would interchange? I called my favorite one yesterday, and they said no.

Otherwise, I need to find out which raw materials to buy to do a rewire the old fashioned way. Speak up - I'm all ears. I found the fusible link on Ebay, but would like to verify the guage.

I'm not an electrician, but can understand basic electrical diagrams and build stuff from them.

Think I'll take a look at my fancy-dancy Ford service manual on CD. I can't believe all the info that's there for about 10 bucks!!

Really appreciate the hand holding, and please keep sharing info about this job.

 

How much of the wiring harness is toasted?

Can you take and upload some digital photos of the damage?

There are a lot of wires, for several different systems on the passenger side inner fender, that would be the hardest to rewire.

On the engine, not to hard.

Drivers side inner fender near the firewall, there are a lot of wires going to the rear of the truck.

Manual tranny or automatic?

 

Thanks again for the reply, Dave. Since you've been so kind, I'll try to answer your questions. The truck is a 5 speed manual. I don't know th e extent of the damage, because I haven't viewed it myself. I called my brother today to try to query him concerning the extent of the damage, but got no where with him. I have a wonderful Brother, and wouldn't trade him for anyone, or anyone else's brother, but attention to detail is not his strong point. He don't know, therefore, I don't know.

What I'm hoping to do now is to head down to the farm this Friday afternoon with some supplies, and maybe, just mabe rig her to run so I can do some farm work with it. right now it has a load of steer manure on it that needs to move 20 miles North (to my farm) and become intimate with some municipal leaves to make some compost.

I'd be very grateful if you could suggest a "tiger team" slew of supplies I might need to get her running so i could get my mission accomplished. As I mentioned before, I have a Ford service manual, a computer and years of experience running and working on everything from a 1940's farm tractor to nuclear reactors, and I think with your help. I might get this thing running again..again,.. again.... It's been on of those trucks - shoulda left it and my money where they were!!! And, I'm FORD guy!!!!!!!

 

Personally, if my truck smoked all of those wires, I'd scrap the whole circuit and just wire in a new one with a switch to control the GP relay. I'd check the GP relay to make sure the contacts didn't weld themselves together first, but if it seems to be working ok, I'd go ahead and wire it up for manual operation.

Just speaking for myself.

 

Matts156, That's basically what I'm thinking of doing. I can hold a momentary switch for a few seconds if needed.

According to my schematic, it looks like most of the wiring is 10 guage. Anyone want to confirm this?

Beagledog.

 

10 gage will handle it.

 

Thanks Matts156, I'm heading to the farm tomorrow and will pick up some 10 gauge on the way. No telling what I'll find.

Looks like we've got a bit in common.

 

Are your glow plug terminals the flat spade type or the round bullet terminal type? If its the round ones, you'll probably need to re-use your original terminals. The bottom line is, the connection between the wire and the terminal needs to be tight since there's over 20 amps going through each wire. I should note also that the 10 gage is enough to handle the power through the glow plugs at the intermittent duty cycle that they require. If it was a constant power draw, you'd need a heavier wire.

Wires may be only one problem. Since all the wires were cooked, that tells me that power was applied to your glow plugs for a very long time. You'll need to do a continuity check on your glow plugs to see if they're burned out. If they are, I hope they're the Motorcraft Beru plugs and when you replace them make sure you get the WHOLE glow plug out when you pull it. If a glow plug comes out with fragments missing, I wouldn't even try to turn the engine over.

And just a reminder from my earlier post, you'll want to make sure your GP relay isn't constantly on. I've seen relays and solenoids weld their contacts together when they get old and near the end of their service life, so even when power's not applied, they're still closed.

 

According to the manual, the GP's ar the bullet type.

Yes, I understand to ensure the GP's haven't broken and dropped chunks into the engine before I hit the start switch.

By relay, I think you mean what the book calls a "solid state controller" - If I'm understanding the schematics correctly, the relay is contained within the controller - correct???

I'll know more in about 3 hours!

 

Not quite within the controller, it's riveted to the top of the controller. So the controller can be disconnected from it and it can be operated manually with a separate switch.

 

Understood - Thanks

 

Thanks to all who offered thoughts and help with fixing my 'ole truck. What I found was the main connector to the glow plug harness was fried. It appears that the two 10 guage wires that feed the glow plugs were what started the fire. After shooting the glow plugs with the test light, I determined that they were probably OK. I cut out the offending connector and spliced the wires together. Then, following Dave's method, I pulled the white wire fron the controller thingy and installed a starter button on the dash to control the glow plugs.

All worked well after that, until I blew a brake line......... That set me back several hours due to local parts houses being closed on Saturday afternoon. Had to make a 50 miler round trip to get brake lines.


I' vegotten started on creating a gallery so I can show some pics I've taken - someone might get some use from them in the future.

Thanks again for the help. I'm back in business!