I recently bought 2 used Ford diesel utility body <NOBR>work</NOBR> trucks. I got a great deal on both, now I know why. They were sold to me with "minor issues", which have turned out to be not so minor. I need some advice now.
The 93 F350 7.3 (non-turbo) is now running great, but has me confused. I replaced all the glow plugs and glow plug relay. The "wait to start" light now comes on as normal. After the truck is cranked, the relay clicks 7-8 times. As it is clicking, the battery warning light flashes and the alternator gauge fluctuates. After the clicking stops, everything goes back to normal. Anyone know what would cause this?
The other truck is a 96 F250 7.3 turbo. It runs rough, and after replacing a few things that I thought would help, I finally took it to Ford for a diagnostic test. I was told that the wiring harnesses and connectors that run under the valve covers have overheated and fried my IDM computer. The repair estimate is $2400. I am not a professional diesel mechanic, just a hardworking family man, but I have been working hard on these trucks. Can anyone help me with directions to replace the harnesses and IDM? Or direct me to a helpful diagram? Or is this something that an "average Joe" should stay away from? Any help or advice would be appreciated!

 

2400 is probably because of labor.

the harness under the VC does that on these trucks.
I dont remember the price, but they are not hard to replace.

I'd replace that first then see if still works rough before I replace the IDM.

I'd go over all the battery connections and grounds on the 93 IDI.
Sounds like it's loosing power someplace.

 

Thank you, Talyn. I have ordered the 4 wiring harnesses ($230), and I am hoping that fixes the problem. On the repair estimate it also says that my ICP is leaking diesel fuel. I'm wondering if it is actually leaking, or would that issue be solved when I replace the bad harnesses? Would I also need to replace it? I have no idea what or where the ICP is, or how it works.

 

On your 93 the relay clicking is the after glow to help with the combustion when the engine is cold. The glow plugs draw around 200 amps when on. Maybe the altinator is getting a little weak as indicated by the battery light coming on.
On the 96, replacing the valve cover gasket and under cover wire harness isn' that tough. Getting the cover off is the hardest part. Also check the wiring plug on the outside of the valve cover, I had to replace 3 of the 4 because of melting on the glow plug pins. On the IDM I have never messed with that so I'm no help there.

 

I got a IDM on ebay for about $200.00 they are about $700.00 at stealership. If u know somone with a 95-99 swap IDM and see it it fixes the problem before u buy one. Also there is a place in Florida I think it is Auto Computer Exchange that sells them reasonable. Hope this helps.

 

I've never really messed with the icp to much but it is a sensor on the front of the driver's side head. It has a three-wire connector going to it. I may be wrong here, but I am about 95% sure that if the icp is leaking it should be HPO (High Pressure Oil) not diesel fuel. ICP = Injection Control Pressure. One thing you might want to try is just unplugging that sensor. If the idle smooths out then that sensor is bad. Also before you go tearing the VC off (which sounds worse than it is) there are several other things to check first.

1) Change Fuel Filter/ Clean FPR (Fuel Pressure Regulator) Screen and check the fuel pressure at idle. There is a shrader valve (tire valve) on the FPR. Use a Cheap tire gauge and check it just as you would a tire. Have rags handy because instead of hissing air you'll have squirting diesel fuel. The guage should spike around 50 psi.
2) Check the oil level to make sure that the high pressure oil pump is actually getting adequate oil to run the injectors properly.
3) Unplug each of the outer VC harness and use an Ohm meter to check the wiring under the VC. There are five pins on each plug. The middle pin is the common ground for the two injectors on that plug, the next one out on each side is the injector wires, and the outer two are the GP wires. If you touch one probe to the middle pin and the other probe to on of the injector pins you should get a reading of around 3-3.5 ohms, and to check the gp put one probe on the pin for the glowplug and the other on a good ground to the battery (not the middle pin). You should see 1.3-1.5 ohms.
4) If step 3 yields the proper results you can unplug the 42-pin harness behind the air box. That is the start of the engine wiring harness. To check these wires you can do it one of to ways. first you can leave the outer VC harnesses unplugged and check each wire or you can plug them back in and check the wholoe circuit.
Dang it I had a paper that had the position of eadch wire on the 42-pin plug but I can't find it now. I guess unless someone else has that info you'll have to go by colors. I do remember that the injector wires are in slots 2-8, 10, and the two grounds (only one for each bank) or in 11 and 12. Pin #1 and #9 are the big pins on the corners and aren't used.

Well that you get you started. I hope this helps.

 

Fixitman these guys hit the nail on the head. start with these steps and get back to us and let us know your results. By the way welcome to FTE.

 

IDM seldom fails, unless you get water in it. It will shut itself down if it detects abnormal current draw, or not enough due to burnt connections going to valve covers. Repair that damage first before trying new IDM.

 

You can get the under valve cover harnesses for cheap on Ebay... did them on mine not long ago. Replace those and see if it runs. If it's still bad you can use a IDM from any 95-2002 7.3 truck

 

Just don't buy anything dorman brand.

 

Thank you all for the great tips! I will try them out, and keep my fingers crossed. I have ordered the wiring harnesses that run under the valve cover, and will replace them next weekend. If that fixes my problem, I'll be happy. I'm hoping that the Ford dealership lied to me, and that my IDM is okay. It appears that the burnt wiring harnesses seem to be a common problem in these trucks. Is there anything that I can do to prevent it from happening again, and how long should I expect them to last? Thanks again!

 

Welcome to FTE! X2 on what Hussler said. I would start w/UVC. It's been my experience that the IDM works or it doesn't. I have bought IDM's (Injector Drive Module which do not compute, so don't let the junkyard think they are selling you a "computer") from the junkyard for very cheap $50 and below. A spare IDM is not a bad thing to carry with you. It is located on the drivers side fender near the firewall and hood spring. If you go the junkyard route any 7.3 IDM will do and be sure to give it a shake to listen for water. If there is water in it throw it a puddle and try the next one. Goodluck and let us know how it goes. Here is a cool site that to check out it will help you get to know your PSD: Tips - Idea - Hints

 

Sometimes bad glowplugs can cause the wiring to burn up so you might want to replace glowplugs also.

If you still think it's the IDM find someone else with a 7.3 powerstroke and see if they'll let you put their working IDM in yours and see if it fixes the problem.

 

Okay, this is what I've found so far today. I pulled the driver's side valve cover and everything looks great under there. No melted connectors, burnt wires, or any sign of damage. I checked each injector wire and there all were 3.2 Ohms. The glow plug wires showed 0.9 to 1.1 Ohms to the battery ground. The pigtail terminals and plug look good, no melting or damage showing. Cowmilker, using your guidelines it looks like my glow plug readings are a little low. If I unplug the IDM, can someone here tell me which pins feed which injectors and glow plugs, and which ones are grounds? I would like to test the circuit. I'm beginning to think that the dealership lied to me.

 

Also, on the Ford repair estimate for my 96, it says that the ICP is leaking diesel fuel.
I checked this morning, and it is. It is diesel fuel, and when I wiggle the plug, it leaks out to the wires. Could that possibly be the reason it is running rough?