Last November I forgot to plug my truck in and it got down to 0, my girlfriend tried unsuccessfully to jump start it. When I got home I jumped it and got it running. I took it down to a heated shop to troubleshoot the glow plug circuit. I discovered it was not getting 12v to the glow plug relay. Also I started it and tried to back it up in the shop, when put in reverse it killed the engine, not lugged it down it was like you shut the switch off. Also I discovered if you turn the lights on it kills the engine immediately. It will not crank with the lights on either. So far I have replaced the computer,ignition switch,batteries, and cam positioning sensor. Now comes the weird part!! I decided to get it running and pull the bulbs out of the back up lights I pulled the drivers bulb first then the passengers side bulb. When I pulled the passengers side bulb it killed the engine. It is not my daily driver so it still sits in my shop. I have a hunch it's a ground issue but I've checked and cleaned up all the grounds I can find and it still has the problem. Anybody experience a problem like this? I'm open to any and all suggestions. Thanks, Loggerman.

 

Strange indeed! So out of curiosity, can you duplicate the problem? If you reinstall the backup bulb, restart, and then remove the bulb does it kill it again or was it a coincidence?

 

Yes, I can duplicate the problem. I also put an indicator light on the glow plugs themselves. It comes on when the glow plugs are actually getting voltage from the relay. As we all know the wait to start light does not mean the glow plugs are actually powered up. This truck will not start unless the glow plug indicator I put on is lit. Not because it is cold but because every time I cycle
the ignition switch it doesn't power up the injectors and glow plug relays. I may have to rotate the switch 5 or 6 times to get the indicator that signals that the glow plugs are actually getting power. It has a new ignition switch in it. I have talked to several diesel repair and Ford dealership mechanics and none can give me an answer. It throws an error code when I put the scanner on it. Not your average problem. Thanks for the response, all help is appreciated.

 

Well, you know the circuit affected.

You need a wiring diagram. Somewhere in that circuit it has a cross-over with another circuit via chafing or other anomaly such as resistance to ground through the insulation. Either just beginning or becoming a more entailer process.

On a side note: If you don't have the STOCK Third Brake Light - Remove it! There is a TSB regarding this.

With a wiring diagram, isolate the suspect circuit by removing the fuse.

Now, perform the same and identify the other circuit through trial and error. Activating things like Wipers, Turn Signals, etc. until it shuts off again. That's the other circuit.

Now, it’s a matter of finding the point of crossover or grounding. Using a Tone Generator, ECT-2000, LoadPro, PowerProbe, and External Power Source, Shot Buddy or something similar.

It all sounds fairly simple. I had almost 18 Hours in a 12' Focus A/C Short. I could have literally replaced the A/C System Cheaper. It was short in the Main Harness where a slice was designed.

So, it takes a while. But, the fix is almost always very simple and takes on a few minutes to repair.

Once you know what circuits are affected, post back and I'll see if I have the Wiring Diagrams.

 

The circuits affected must be the lights and back up lights. Like I posted above it will not crank with the lights or park lights on. It will also shut off the engine when you turn on the lights. As stated above it also kills the engine when you put it in reverse. No other function affects it. Also the ignition switch has to be rotated numerous times to activate the glow plugs. It will not start or even smoke until the light I wired to the glow plug circuit is activated. Thanks for the response and keep them coming.

 

You may well have a short in the Column Harness at the root of your problems.


Just out of curiosity, how exactly did you wire the GP Light?

The Bottom Line is:

1. That does not necessarily rule out any other circuit.

2. You have to begin eliminating them one-by-one until the issue does not reoccur.

3. Then the tedious Trask of chasing the Rabbit down the Hole begins.

4. You could also have a (+) that is affecting the (-) and vice-versa. The ONLY way your going to find out is to Dive into it.

Lastly, What year, Sub-Model, and Drive Unit is it? i.e.: 99.5 F250-SD XLT 4WD CC

 

I wired a light off of the cold side of the glow plug relay. The post that is only hot when the relay is excited. It is one of the two larger wires.

 

Finally got back to working on this thing. Today I started by pulling all the light fuses and started plugging them in one by one with the engine running. I was able to install all the fuses until I got to the park lights fuse it not only killed the engine but the engine will not crank with the park lights (daytime running lights) fuse plugged in. The lights work but the engine will not crank or run with that particular fuse plugged in. I have checked and cleaned every ground I can find. In checking the relays it seems I lose the ground circuit to the pcm,the fuel pump and the injector module. I assumed it must be a problem with the fuse panel so I took it out. On further investigation I discovered by separating the back of the fuse panel it has a burned circuit on the circuit board. When I ohmed the circuit board it went to the ground circuit on the pcm relay. I have one ordered, hopefully this is all that is wrong. I will post one way or the other

 

I would like to add one comment to your very good job of trouble-shooting. When a circuit board gets burned, it is often from too much current. This can be the result of a bad ground connection elsewhere in the vehicle. When the circuit with the open ground tries to send current to ground, the current finds alternate paths (such as the circuit board) back to the battery negative. I hope you have found the only problem.
Larry

 

This problem originated when my better half tried jumping the vehicle in sub zero temps without the block heater being plugged in. I have a hunch she may have hooked the cables up backwards. I will know more when the new fuse block is installed.

 

Finally got the new fuse box assembly and got it installed. All problems disappeared. The circuit that was fried was the ground circuit for the relays. Glad this problem is resolved, thank you to the few that responded with suggestions!!