Hey guys, have myself a 96 F-250 that ive been trying to get running for a while now, but ive been having the same problem consistently now. Its hard starting (wasnt when the problem first appeared but now its really hard starting), no power, and when it does get running it spews a lot of white smoke and makes an odd chuffing noise. Ive narrowed it down to cyl 6 and/or 8 by unplugging the valve cover connector there. When I do, the chuffing stops and most of the smoke goes away. I have Forscan so im able to do a Buzz test, comes back saying cyl 6 and 8 high to low fault. Ive probed every connector and checked for broken wires or high resistance and everything checks out, all 8 injector solenoids read 3.2 Ohms and I haven't found any problems with continuity between any of the wires between the IDM and engine and the IDM and PCM. So far in testing I have: swapped the UVCH between cyl 6/8 and cyl 2/4, buzz test still points to 6 and 8. Swapped a solenoid between cyl 6 and cyl 4, buzz test still points to 6 and 8. Swapped the full valve cover harness between passenger and drivers side banks, buzz test still points to 6 and 8. With that I am confident that the problem isnt the UVCH. I rebuilt the injectors previously in my attempt to fix the problem but it persists in the exact same way so I highly doubt its the injectors. I also replaced the valve cover connectors (Reused the old wires but replaced the connector bodies as I had a couple with broken locking tabs) so that is ruled out as well. Interestingly, I have also tried swapping my IDM with one I got from a junkyard super duty. On the old IDM a buzz test would give the high/low fault on 6 out of 8 injectors, but the junkyard IDM only gives the fault on injectors 6 and 8, which given how I can unplug the harness and the chuffing/smoking stops I know the problem is isolated there. All that combined with the really hard starting (HPOP builds good pressure and ive verified fuel pressure, so thats ruled out as well) leads me to believe that its a bad IDM and I just got unlucky and the junkyard one I got was also bad. Anyone have any advice or additional testing they can give me before I go and drop $350+ on a reman IDM?

 

https://www.dieseltechchatt.com/

 

i think you have a short in the wiring if with a different IDM problem is showing on 6 and 8

good wiring diagram here to test ohms on
https://www.ford-trucks.com/forums/1...load-test.html

 

That sounds like exactly the kind of thing I need to try, thanks. I'm a little confused by the process however. Am I supposed to hook up the light directly to battery pos and neg, with which ever wire I am testing as basically an extension on the positive side?

 

use the pin out to ohm it out, dont do the load test yet

 

Already did that. I found this post last night and followed the directions in the attached pdf, seems like a cut out from a factory service manual or something. Following test procedures there everything comes back to "IDM internal fault, replace IDM". Just for reference the codes I am getting from a buzz test are P1276, P1278, P1293 and P1294.

 

could be bent pin on IDM connector for the open P1293 and P1294.

 

How's the engines health? Any significant amount of blow by?

Also have you tried swapping solenoids from injectors 6 and 8 with other injectors? Or swap the problem injectors to other cylinders to verify that it's indeed an Injector/wiring problem?

Did you rebuild the injectors? Or have them rebuild?

I had a similar problem with my 00 when I first got it, turned out to be a bad PCM that cured the misfire knock/huffing sound, but still had the smoke due to low compression.

 

Thanks for the reply. This is a freshly rebuilt motor, there is no blow by. I have swapped solenoids between #6 and #4 and ran a buzz test again, still said 6 and 8. The injectors I rebuilt myself, but I very carefully did them one at a time so im confident that there is nothing wrong with them. Heads have new injector cups in them that were installed by a shop when I built the engine, just to answer that question before it gets asked. PCM is a new reman, the truck is actually a diesel swap that I pieced together from a couple different trucks. The engine/trans were an auto but all the wiring (including them IDM) were from a manual that I never saw run, had to get a new PCM since you can go auto to manual but not the other way around.

 

What kind of rebuild did you do to the injectors? Full disassembly? If so any chance those injectors are bad , that machining might of been needed?

​​​​​​Check armature clearance (.003-.004)

 

Full disassembly. I cleaned everything in an ultrasonic cleaner and inspected as I was putting them back together. Everything looked fine, no scoring or odd wear, but I did find one injector that had a broken fuel spring but I replaced it with new from the kit I got. Armature clearance was the same on all, between .0025 and .003. From what I read that should still be fine. The smallest shims the kit i got came with were .002, so I didn't want to shim it beyond .004.