Help 7.3 missing, no codes, did buzz and contribution tests

[Probuilder]

It is a grey cps in it right now. Should I swap it out to see if that fixes the problem?
Or will it not make a difference when actually running?
Should I check the pressures on the ipr, ipc oil pressure, etc?

[907DAVE]

I would swap the CPS with a black or dark purple one, clear all codes and re-test.

The CPS will have no effect on the Buzz Test, but will effect the Contribution Test.

This is not going to cure you misfire issue, instead make things a little more cut and dry. It will eliminate the phantom 3&8 misfire that the gray CPS is know for.

But I am going to put my money on that #8 injector being bad.

Good Luck

[Probuilder]

Dave,
Did the CPS swap and retested.
Still got these codes:
KOER:
P0476 Exhaust Pressure Control Valve Range/ Performance
P0541 Intake Air Heater- Not used.
P0640 Intake Air Heater- Not used.

KOEO:
P0475 Exhaust Pressure Control Valve
P0640 Intake Air Heater- Not used.

On the buzz test the last 2 buzzes were dull in sound and not as fast as the others, just like before.

I don't have the FU Chip in the truck at all. I took it out to perform all tests.
Any help would be appreciated.
How do I test the ICP, IPR sensors? I know that you have info on here on how to perform all these tests, but I can't find it.

[SICKS-O]

i see that you posted you already did the UVC harnesses, did you replace just the injector/glow plug harnesses or did you do a valve cover gasket as well? a scan tool will only get you so far on a 7.3, but can point you in a direction, from there things are going to get more hands on. since cyl 7 and cyl 8 dont have a strong buzz that narrows things down a bit.

there are a few possibilities, wiring harness chafing, UVCH or valve cover gasket connector problem or injector failure.

i would first check for chafing of the engine wiring harness, particularly in the area above the drivers side valve cover where the junction block is. if there are any chafes repair them and retest. if the problem is still there unplug the engine harness from each valve cover gasket and test the resistance between the connectors and the appropriate pins at the junction block, the continuity should be good. if not that problem will need to be addressed. the next step is to check each valve cover gasket pin for each injector circuit (other than a dvm you may need a special tool that plugs into the valve cover gasket that is available, never tried doing it without it) the resistance should within a certain margin. (i cant remember the specific amounts off the top of my head). if the resistance is within spec there could still be an injector failure but possibly an issue with the engine harness between the valve cover gaskets and idm or the idm could just be no good.
if the resistance at the outside connection of the valve cover gasket is not within spec (specifically cyl 7 and 8) then you will need to pull the valve covers and unplug the UVCHs. test the resistance at each pin from both sides of the valve cover gasket connector to eliminate that as a possibility, obviously there should be no open circuits and should have good continuity. from there you want to test resistance at the UVCH connector itself to get another reading for each injectors coil resistance and see if it matches the reading you originally got from the outside. if it the resistance is now within spec there then is an issue that was over looked with the valve cover gasket itself or the engine harness. if the resistance is still not in spec you could go as far as testing the continuity of the uvch but more than likely the injector(s) have failed and need to be replaced.

if you get all the way to the injectors them self and the resistance and continuity tests have checked out good it is possible there is still an injector failure but since there isnt any hard evidence yet i would swap cyl 7 and 8 injectors with 2 other cylinders (using new o-rings and washers of course) then retest and see if the problem followed the injectors that were originally in 7 and/or 8. if the problem didnt follow those 2 injectors and stayed at 7 and/or 8 then things get more interesting. at that point the IDM is starting to look suspect but post back your evidence before i get into that lol.

good luck.

[Probuilder]

UVCH and gaskets were changed out.
Wiring harness between the IDM and valve cover gaskets has been changed out and tested, just did that last night. (Since I had an extra one laying around)

I will get a o-ring kit and swap out the injectors to let you know on that.

Thanks for the help

[SICKS-O]

no problem, did the best i could for 3am lol. since you have OKed the wiring before spending any money or getting your hands to dirty i would test the resistance of the injector coils with a digital volt meter, i dont think you will be able to do it easily without the tool they sell that plugs into the valve cover gasket, it has color coded pigtails for dvm leads. you may be able to make your own test harness if you have any spare harnesses laying around.
i think the easiest thing to do would be to uncouple the junction block that is on top of the drivers side valve cover and test the injector coil resistance from the pins on that block, of course you will need to know which pins are for the injector circuits. when i get another break at work i will grab our 7.3 service manual and post the acceptable resistance range for the injector coils. following this procedure will save you time and trouble. if the resistance of any of the injectors doesnt check out then you will know you will need to replace them, if the resistance is good there is still a chance that an internal part of the fuel injector(s) has failed and i will try to help you diagnose further.

-Joe

[Tempsho]

Lots of good information in this thread for troublshooting a 7.3L that's missing! Good luck with your problem and let us know what fixes it.

[Probuilder]

Does anyone have a link to a wiring diagram for the junction block above the drivers side valve cover? I am looking for one that will tell me which wires run to the injectors, to test them.

Sicks-0, First thank you for all your help.
Why am I getting a P0475 and P0476 code in the computer? What is this pressure valve? Now I am not getting the boost that I used to either, and the truck is consistently getting worse, as far as running and power.
KOER:
P0476 Exhaust Pressure Control Valve Range/ Performance
KOEO:
P0475 Exhaust Pressure Control Valve
Just a thought, but if my EBPV sticks when I am warming the truck up, it will smoke and have no power. Could this be a problem, and defueling the truck? Or would that not have an effect on the buzz test? (Probably not but just a 4 am thought that ran through my head when I quit working on it last night)

Again thank you all for your help.

[907DAVE]

I can shoot you some diagrams if you like, just need your e-mail address.

[Probuilder]

Dave,
Probuilder72@gmail.com
Thank you