Does anyone know what the sequence is of the cylinder contribution test is?? Does it follow the number sequence of the cylinders 12345678 or the firing order 1-2-7-3-4-5-6-8?? Mine is a 97 and the second cylinder killed in the sounds strange but it says cyl 4 failed? This would make sense if it does by bank 2468 1357? any imput greatly appreciated

 

The Superduty is numerical order, I'm unsure of pre-SD. The best way to know for sure is to feel the solenoid you expect to fire next. If your VCs are not popped yet, unplug the Passenger side wire harness. If you then hear two injectors in a row without a pause, then it's firing order instead of numerical order.

 

PC/ED says it runs the CCT by cutting the cylinders out in order "1 through 8", but it doesn't specify if it's numerical order or firing order (both start with 1 and end with 8). When it cuts a cylinder off, I'd have to imagine the PCM is testing how the other cylinders react to it. I'm sure there's some fancy algorithm to determine how well each cylinder does when other cylinders are cut, so the sound probably doesn't mean much in relation to the results.

 

The UVCH link in my signature shows the firing order and the CCT order for a Superduty. I don't know if the SD PC/ED matches the OBS PC/ED, so physical confirmation of the CCT order is needed on the OBS - unless somebody in the OBS forum has this info.

 

Well it is probably safe to say the second cylinder that it tests is 2 since that is the 2nd in numerical order and in the firing order? I am getting a faint air thump seemingly from the intake when it kills the second cylinder but not on the rest. not bad like a non functioning exhaust valve would cause but I do notice it slightly. I have the drivers side valve cover off and everythings appears to be working good. Paranoia as I just rebuilt the engine 500 miles ago.

 

There is no testing order of the cylinders during a CCT on Super Duty 7.3s. All 8 cylinders are tested continuously throughout the test. That's from the PC/ED. What I posted above regarding the order of cylinders is also from the PC/ED for 1998 model year engines. The test runs the same way on earlier model years. A CCT on OBS trucks sounds horrible, especially during the second half of it when each cylinder bank is shut down for a period of time. If a fault is detected during the first half while only one cylinder is shut down at a time, the second half isn't run at all.

 

Was valve work done at the same time? New valves, or the seats cut?

 

Not wanting to be rude, my friend - but this is inaccurate. The UVCH link has a page from my PC/ED, showing the CCT sequence. Just as an add-on to the conversation, here is a Buzz test on my 2000 Superduty (Da Big Stink) - for those of you with stereo speakers on your computer:

 

I believe you're confusing a cylinder contribution test with an injector buzz test.

On OBS trucks, the CCT actually does shut down one cylinder at a time during the first portion of the test, then it shuts down a cylinder bank at a time during the second half of the test. The second half of the test doesn't run if any faults are detected during the first half.

 

Ok, I'm confused...isn't the buzz test the same as the CCT test? If not, I guess I need to figure out how to use AE to do it, and try it out!

 

Now you see? That's what happens when I stay up late... I turn into a pumpkin. I went back and corrected my post, thanks for keeping me honest.


The Buzz test is conducted with a cold engine while it is not running.


The Cylinder Contribution Test is conducted on a warm engine with the engine idling, no A/C, and in gear with the brake on [LINK]