I have a 97 crew cab dually 7.3 power stroke. The number 4 cyl 2nd on right facing the truck that will not fire. Replace injector with new and swapped with known good injector next to it. Replace valve cover gaskets and connectors that are soldered in, replaced the IDM and checked to make sure I have continuity all the way to the power control fuse box but still no fire on that one cylinder. Push rods don't appear to be bent or either valve stuck. The truck has a bad miss cold and is hard to start but seems to run great after normal operating temp is reached. But still no fire on 4. Pulling the injector wire has no effect on that cylinder. No oil coming out of the injector like the others but moving the suspect injector works fine in any other cylinder. Fuel pressure is good so I am at a loss and new to the computerized versions of diesel engines. Anyone have a clue as to what to check next? Oil pressure is good in that all other injectors work great. Oh and new glow plugs

Thanks for any advice/help anyone.

 

I'm no expert by any means, but to me is sounds like a bad wire or connection to the dead injector. I would test the wires for continuity starting with the under valve cover wire and working backwards. Unplug the wire from the gasket and check, then the gasket, then from gasket to idm.

 

If you're 100% sure that there is no oil coming out the spill spout of that injector and it works fine when you swap it into another hole, then it has got to be an electrical issue. Either it is a bad wiring connection somewhere or it is a bad IDM. You say you have replaced the IDM though, so I doubt it is that. You say that you replaced the VC Gaskets and the pigtail on the engine harness, but have you replaced (or swapped) the under valve cover wiring harness? You might try just swapping it with another one and see if the issue follows the harness or not.

The only other thing I can think of is that you might want to give that cylinder a compression test and make sure you're getting good compression. If the injector would be firing and the cylinder wasn't making good pressure it is possible that you would still get a miss. If you're 100% sure that the injector isn't spitting oil though, it really sounds like an electrical issue and not a compression issue.

 

Here is a very good guide that might help in troubleshooting ...

GB Remanufacturing - Tech Bulletin #103

At the bottom of the document is a downloadable PDF version, larger and easier to read.

 

When I did the continuity test I started from the connector at the injector and worked all the way back to the connector at the power control box.

 

Thanks for URL and down loaded it. Will try that and the harness swap to see what I get

 

So you disconnected the IDM and tested the wiring all the way to that point?

 

Not all the way to the IDM. Up to that large connector that goes to the power control box with all the big fuses in it. All fuses are good and relays seem to be working but I don't know how to test them.

 

Pull the connector at the IDM (there is a 10mm bolt in the center of it that takes it off the IDM) and ohm the injector wire for that (#2) injector back to the end of the UVCWH connector (right where the injector itself plugs in).

Here is the pinout at the IDM:

Looks like it should be pin number 22. Pin 23 is the common for that injector and I would ohm that one out as well. In fact, while you have it apart, in addition to ohming the wiring from end to end I would ohm between pins 22 and 23. With the injector plugged in you should read around 3.2 ohms. That is the value of the injector coil. If you're seeing something different than that, then ohm between the two pins on the injector itself and compare the readings. If they're substantially different, you have a wiring issue for sure.

 

Great I will try that and thank you

 

Wasn't it #4 that wasn't firing? That would be pin 7. Pin 23 is still the common for that one.

 

This is great but you had me on 22 which is cyl #2 not #4 unless I am mistaken (2nd cyl on the right facing the vehicle going from front to back) there is a blue wire and a yellow wire coming out of the injector. At the connector on the VC gasket which wire should blue go to on the harness? brown with a light blue stripe? Which would be #7 pin on the IDM. I am not getting any continuity to the blue wire on the injector.

 

I think you are correct according to the diagram and yes #4 is not firing. What color wire is the blue wire from the injector supposed to tie into the harness? Looks to me like brown with a lite blue stripe

 

Yeah sorry about that. Nice save Bill. I was thinking second one on the drivers side, but said number 2 instead, which of course would be the first one. Yes the wire would be brown with a light blue stripe (BR/LB).

 

Thanks Nate! Just for the record, Nate knows way more about these engines than I do! I wasn't trying to one up or anything, just didn't want any confusion about wire color. LOL!