bought a new to me truck yesterday. craigslist deal, traded a trailer i had no use for in the foreseeable future. pulled a 3/4 ton diesel truck home 22 miles with a 1980 bronco with a straight 6. long long drive

truck is a 1995 F-250 7.3L DI 2WD regular cab, long box, dual tanks

PO said that the fuse for the glow plugs had blown and he hadn't had the right so fuse so he replaced it with a larger (50A) fuse. the story seemed shifty from there. short version was that they cut the two wires going to the fuse box for the glow plugs

when i got it the distribution box was disconnected. the wires for the glow plugs were cut (red wire with a thin green stripe, one appx 10ga, one appx 14ga) and the yellow wire feeding the distribution box was disconnected. i checked the thicker wire with a multimeter. reading was 0V against the negative battery terminal, 13.4V against the positive terminal.

truck turns over fine, and most of the accessories seem to be working (radio isn't coming on, cab lights didn't work, etc)

shouldn't the thicker wire be a hot wire? it was reading as though it were a fully grounded wire. Does someone have a good wiring diagram i could use while chasing this down? the dash gauges aren't reading, so i'm going on the assurance of the PO that the tanks both still have fuel in them. any good method to ensure that fuel is getting to the engine? I'm open to suggestions here.

i brought this home telling my girl "no worries babe, i'll have it up and running in an hour..."

 

It will probably take a little bit over an hour, but doable.

Just to get you started here is a simple diagram on the glow plug circuit ...



I'm not quite sure all you are saying such as wires at distribution box are cut .. under hood fuse box? That's not good depending what PO did. But everything is repairable with time.

 

yes, the under hood distrobution box on the drivers side inner fender well. it was removed from its cradle, disconnected, and the wires going to the glow plug fuse were cut approx two inches down, then the sheathing was stripped back on both sides.
if i'm reading your diagram right, then the R/LG is actually serving as a ground for the solenoid?
is the PCM connector the silver box on the inner driver's side fender?
what is the "42 way connector"
i'll get a better look tomorrow if the snow stops, and try and take a picture if i can.

thanks for the diagram, that'll really help

 

The silver box is the IDM. The pcm is in the cab behind the plug in beside the IDM. You can see it if you remove the E brakes 3 bolts. It's removed by loosening the inner fender and wedging it down and removing from the outside if you need to get it out.

 

R/LG wire is key power - 12 volts.
The dash-ed wire goes to the PCM.
It grounds it when it wants GPR to activate.

30A fuse is fuse #22. If the fuel heat shorts, quite common, then it blows that fuse. That fuse also controls power to the PCM. Truck will never start is blown. If it is blown then try unplugging the fuel heater wire located on the drivers side of the fuel filter canister, second wire from top. It is hard to get off because it is a spade connector, like a speaker wire. The heater is really not needed but can be repaired if you want to.

One of the large wires on the GPR goes to the starter solenoid and is hot all the time. The other large lug should have two wires on it and each goes down to the valve cover connectors. As you can see the outside connectors on each plug supplies voltage to two glow plugs. Pins B and D control two injectors and pin C is injector ground.

The box you are referring to is the IDM. The PCM is located further down and most of it is located behind the emergency brake kick panel.

 

i wasn't able to figure out which wire you were talking about on the fuel filter. i saw a connector on the passenger side, but no wires on the drivers side.
i tested continuity of the R/LG wire and it tested good, same with the feed to the GPR from the starter solenoid.
with the key in either on or off position the 10ga wire is grounded.
i also noticed that the wait to start light doesn't come on. i'm going check continuity between the 10ga wire and the PCM connector. i'm worried its more than just a small problem. my personal guess is that something past the fuse is bad, but that when they replaced the fuse with the wrong size it fried something else. i'm gonna take some pictures and i'll post results, whatever they be

 

Odds are the fuel heater is shorted as stated above. No wait to start light is another symptom of fuse #22 blown. Fuel heater is past the fuse.

And yes, most of the time it is simple stuff.

 

traced the wire back from the distribution box. i can't imagine it being anything but a dead ground. i pulled the ignition switch box (the box directly attached to the steering column that is triggered by the key). full continuity between the cut end of the wire and the end at the switch.
the wire also connects to the fuse box under the dash that controls the gauges and buzzer, which explains why none of the gauges worked.
unless someone can tell me what else would cause this, i'm going to figure that there is a dead short somewhere.

 

Sorry, I'm clueless where you're at in this project. Initially I thought you were working in the engine compartment fuse box but now you're tearing apart the ignition switch. You need to be more specific why you think you have a dead short and where / why?

Can you say which fuse in the engine compartment the PO replaced from a 30A to a 50A? Not a trick question, answer is yes or no.

 

yes. the owner switched fuse #22 on the distribution box from a 30A to a 50A, then at some point cut the wires on the back side of the distribution box coming out of the #22 fuse location. there is currently no fuse there.

using a digital multimeter i checked resistance (good way to determine continuity) and voltage between the negative and positive terminals of the battery) and the wire providing voltage to the number 22 fuse. it had full continuity between the wire and the negative terminal, none to the positive, 13.2V to the positive side, 0 to the negative. this is how i determined that the wire is grounded.

since this wire provides positive current to the #22 fuse it should not be grounded. it should either be neutral (not hot or ground, as is the case with a switched wire with the switch off) or hot.

tracing this wire back i determined that the wire goes through the firewall (it was the passthrough, not the pin connection). at some point the wire then goes to the in dash fuse panel, specifically the fuse for the gauges and buzzer, then continues to under the steering column. under the steering column it terminates at the ignition switch box. i don't know what else to call this box. it is a plastic piece with a protruding metal rod that fits in a hole whose motion is controlled by the rotation of the key. turning the key to acc, off, on, and start controls which circuits in the "switch box" are on and which are off.

i tested continuity of the wire from the cut end under the distribution box to the in dash fuse and to the switch box under the steering column. the wire had no resistance, therefore, full continuity.

from what i can tell, the wire should be a neutral circuit (neither hot nor common ground) until the key is placed in the "on" position at which point the wire should be made hot. the switch box under the steering column has several hot feeds used to create a full circuit depending on which position the key is in.

I have not yet checked the hot feeds into the switch box to ensure that they are indeed all hot. I ran out of time and daylight. however, since the wire feeding the distribution box (the same one coming out of the under column switch box) has full continuity with common ground, it must be grounded somewhere between the under column switch box and the distribution box.

i do not believe the fuse was blown due to any fault "downstream" of the fuse. i believe the fuse was blown due to a dead short on the feed wire. because the fuse was replaced with a fuse of a larger capacity i do not doubt that there may NOW be reason to believe that there is damage to components of the circuit (i.e. glow plug relay)

not a trick answer, i know which fuse he replaced.
i'm not trying to be difficult, a lot of times i write my responses when i'm outside working on the truck, it all made sense in my head... really...

 

i've been tracking this down with no luck as of yet. anyone have any other ideas as to what to cause this wire to be grounded?
i don't want to have to tear the dash completely out to try and find it, but i don't want to have it not running even more...

 

Remove your fuel filter, remove the fuel stand pipe (standpipe is left hand thread) remove and unplug fuel heater install new heater and filter, connect two cut wires and install 30 amp fuse, enjoy.

 

Here is a photo of the wiring connections on drivers side of the fuel filter canister. Second connector from top is the fuel filter heater. Unplug it and see if your short goes away. You might not have the lower connector on the 95 as I think it is located in a different place.

Top connector = Fuel filter restriction sensor.
Lower middle connector = Fuel heater.
Lower bottom connector = Water in fuel sensor connector.

 

Agree w/ wrenchinT444E. From all you've written it sounds to me like the two wires cut in the engine compartment distribution box are the two sides of 30A MAX FUSE #22, correct? If so unplug the fuel bowl heater/preheater wire as previously described by Hussler. It'll run w/o it & if it does this is why the PO tried to bypass the fuse, thought he was bypassing the problem but he made it worse. Since the PO "played" w/ the wiring, just a thought here, maybe you should get a CPS at NAPA or local auto parts store & throw it in too, "just in case" that's another problem PO had & couldn't ID. Just my 2 cents worth.

 

okay. been out tearing apart wiring for the last two hours.

it is not the fuel heater, though the fuel heater may have indeed been the original cause

the problem is that the wire feeding fuse 22 in the under hood distribution box is grounded, and not becoming energized when the key is turned to the on position. i do not where it is grounded, or why it is not becoming energized.

does anyone have a full wiring schematic for a 1995 diesel? i need more than just one circuit, because the R/LG wire also provides power to other circuits.

thanks...