The other day I started my truck and everything was running good and then after 15 minutes i come out to find the truck is running very rough. It sounded like the motor was running on 6 cylinders. It had no power and the check engine light was on. I finally got a chance to look at it today and it still ran rough so i started pulling the wiring harnesses to the injectors. The passengerside harnesses made no difference in the idle but the second i pulled either of the driverside harnesses there was a immediate change in the idle. What could cause this and how can i check it?

 

Sounds like it is the harness. I have seen some melt down completely, and some allow oil into the wire harness itself causing problems. Sometimes it is on the inside of the valve covers. the '95 powerstroke's are notorious for having rough idles or drivibility issues as they get older. I would remove the valve cover, and inspect the valve cover gasket/wire harness.

 

when it running rough like that is it smoking alot?? greyish smoke?? i would say if it made no difference when u unplugged them i would look at the plugs close see if there is some melted plastic. you could check with a multi meter to see if you have continuity through the GP and INJ harnesses as well. they are notorious for going bad just like that. each plug on the VC gaskets services two INJ and two GP

 

I agree, however, the inside wiring from the connection to the injectors could be burned up. They will tell you you have to buy a new wiring harness. You don't. You can get new plug ends and wiring from different outfits. If you can't find one give me an Email and I will find where you can get one.

 

Pulled the passengerside cover off tonite and found that the front harness was melted at the valve cover so both the harness and the valve cover are screwed. I have a spare valve cover gasket but might have to wait it'll tuesday for the new harnesses( need two because the other harness was so bittle it broke when i went to take it off). The harness melted on the outside pin which looks like the glow plug pin. Should i replace the glow plug it connects to( just replaced all of them last year) or is this where they normally melt? Also i was looking at the harrness that connects to the valve cover on the outside and the outside pin on the back harness looks like it got a little hot once and blackened but didn't melt the connector, should i replace the main harness or is it still ok?

 

I'd change the plugs again since you're already in there.

 

cookie is right if your in there already it wouldnt cost too much to change the GP's too. have a good look at the top of engine harness that plugs into the VC see if any of the plugs have been buggered as well. i would think that the drivers side is in not much better shape too, you should have a look at them too. ford wants an arm and a leg for that harness, see if u can find a good used one. just my .02's

 

So i replaced the valve cover gasket, glow plugs and injector harnesses and the truck runs good again. The CEL is still on but the truck runs great. I will have to try to get the codes read to see whats wrong but at least i have vehical again.

 

Well done 300inline6! It's good that you where able to do alot of this work yourself to keep the cost down.
Fortunately, on my '95 my harness hasn't had to be changed, and it doesn't have that brittle feeling, but I have changed both inside valve cover gaskets and two connectors. I changed the glow plugs at the same time of course, and all this was done a couple of years ago.

As for the CEL (check engine light) you will need to retrieve the codes, as it can often be several things.
One thing I have done (which often can lead to a CEL) is completely disconnected the fuel cannister heater ! There are two wires that go to the drivers side of the fuel cannister (which holds the fuel filter) and I believe it is the bottom wire, I cut...and have just left, and all has been fine...since I did this a few years ago. Living here in southern B.C. in Canada I don't believe we have a need for heating the fuel, although for those living in areas where the temperatures dip down into the low "negatives" for lengthy periods, I wouldn't suggest this, as I believe diesel fuel won't gel until the temps get really quite low.
At any rate, disconnecting the fuel heater can help to illiminate one issue that can bring up a CEL. Also, for those that don't know, if the heater element in your cannister deteriorates (they all do eventually) and shorts out, it will blow the fuse, and I've heard of many that could not get their trucks to START when this particular fuse blows.

Other CEL situations are a lack of oil volume/pressure to the injectors, IDM issues, PCM (power control module) issues etc.

Best of luck in your CEL search, and let us know when you find out what it is!

PSD2000

 

Just a quick note, you do not have to replace the complete harness if the outside plugs burn up. Ford sells the plugs, not the wires just the plug.??? but you can get the full kits including the wire from several suppliers and a lot cheaper. Another screwing from your frinds at ford

 

I never did get the codes read but when i checking everything over again i did find my IPS plug not quite in all the way. After ajusting it and getting it to plug all the way in my CEL light went out. I guess it pays to check everything a couple of times when you put it back together. Thanks to everyone who helped me out and thanks zardo47 for the heads up on the connectors. its nice to know i can replace those.