Can anyone tell me what this is? When I had my truck on the scanner after my injector install on Sunday, I did an injector buzz test and then saw a cylinder contribution test and had the snap-on scanner perform it. It came back with something about #7. I am also still experiencing white smoke on startup and don't know if thats normal for a few days or if I blew an O-ring or something.
Deputydog
The cyl contribution cuts out one cyl at a time and measures the increase in fuel rate among the other cyl's to see if there is a weak cyl. If you get a code for a cylinder during the contribution test that cyl is not contributing the same amount of power as the other cylinders. You could have an injector problem, ring/compression problem, valve problem, etc. Most likely since you just had your injectors out you probably have an issue with the # injector.
On the cylinder contribution the "basic" concept is to systematically cut out certain injectors one at a time and see if you get a drop in engine rpm when it happens. Dependent on how much the rpm's drop, or how much the PW has to increase to maintain the same rpm, you can tell that cylinders contribution to the engine's running.
A weak cylinder will not show much change when turned off, a strong cylinder will completely change everything when cut.
It's a little bit more involved on the newer computers in the superdutys (they don't actually drop rpm each time anymore) but that's the basis of it.
On Edit:
It is also kind of funny to think about....but the test measures absolute change....not necessarily positive or negative change. So you could actually throw a specific cylinder if it was too strong relative to the others, lol. Although that is really not normally a practical scenario.
A weak cylinder will not show much change when turned off, a strong cylinder will completely change everything when cut.
It's a little bit more involved on the newer computers in the superdutys (they don't actually drop rpm each time anymore) but that's the basis of it.
On Edit:
It is also kind of funny to think about....but the test measures absolute change....not necessarily positive or negative change. So you could actually throw a specific cylinder if it was too strong relative to the others, lol. Although that is really not normally a practical scenario.
So it was telling me #7 cylinder, I should perhaps pull that injector and inspect it? My truck seems to run really well, but still have a lot of white smoke on startup and it clears up after afew minutes. Don't notice it going down the road.
Are you using AE? You can pull up a Cylinder rotational value... Pull up all 8 and see if there all reading the same or close to the same percentage. If #7 is looking differant then the others then I would look at it.
Also was the truck warm when you did the CCT? Run it several times and see if you get the same one too... Sometimes they will just throw a code for no reason...
Also was the truck warm when you did the CCT? Run it several times and see if you get the same one too... Sometimes they will just throw a code for no reason...
FWIW, if the truck seems to be running fine, and you do not have access to a flowbench you should just leave it be because knowing that an injector is low will only frustrate you without a bench to see how much, and to zero it back in.
Don't forget, you could easily have it not running fine if you're not carefull. And again, without a flowbench to see what's going on you'll be chasing your tail big time and pulling injectors all the while over and over and over again.
Now if you think you have a real issue, like with the smoking or similar, that's different. But if your issue is failing the cont test and you think it's running fine, leave it be if you can't flow em.
Two Cents.
Don't forget, you could easily have it not running fine if you're not carefull. And again, without a flowbench to see what's going on you'll be chasing your tail big time and pulling injectors all the while over and over and over again.
Now if you think you have a real issue, like with the smoking or similar, that's different. But if your issue is failing the cont test and you think it's running fine, leave it be if you can't flow em.
Two Cents.
I know with AE you cant kill one cylinder like that, but maybe other scaners have that ablity? You could also build an injector breakout box...
I have 1999.5 F350 with 7.3 and have been having trouble with rough idle when cold and rough start in the winter, no start if Truck sits out in the cold several days, has to be plugged in for it to start then. Started to upgrade and change equipment starting last year. New CPS, new IDM, glow plugs and gasket and wiring. Truck still had rough idle issues when cold, problem went away when it got warm. Bought a computer test system and buzzed the injectors and 7 and 8 sounded totally different than others. Additives helped the rough idle a bit but did not get rid of the problem. Finally just purchased a set of rebuilt injectors (7 AD and 1 AE) and just had them installed. Truck seemed to run OK without any load on it, finally just did 300 miles with my cab over camper on the truck. At around 150 miles the truck started to run like hell at low RPM and at idle, almost wanting to stall. Made it home another 150 miles and right around then when in town started to run like hell again.
Took truck to the shop and they can not nail anything down, checked the wiring which they had done when the glow plugs were changed and supposedly all wiring is good. I have tested the truck and only code is the Cylinder Contribution code for #8. The Cylinder Change in Rotational Velocity also shows 0 to less than 1 for all cylinders except about 5 for #8. The AE injector in number 8 is recommended for these trucks, the buzz test sound the same to me for all cylinders before 7&8 were totally different. I have purchased an AD injector to put in number 8 but I don't think that will solve the big problem, it may get rid of the code for number 8. The check engine light is not on and the code related to Cylinder 8 may be normal since the difference between the AE and AD injectors. Without the load on the truck it seems to be running OK, going to put the cab back on and run it for some miles. Trying to see what is going on, need a reliable truck, the rough running was really bad and again seem to come on after running some miles with a heavy load. These injectors are totally rebuilt and are tested by the shop but again don't know if some of the issues would show up under such tests. Right now leaning toward buying all new injectors and having all replaced, unfortunately nothing is returnable even though they have warranty. Trying to see how we can nail this down and figure out what is going on. I have purchased the computer system for testing the truck so can look at most data. Don't understand why there is no miss fire count for any of the cylinders even when the truck is running like crap. Any ideas is appreciated.
Don
Took truck to the shop and they can not nail anything down, checked the wiring which they had done when the glow plugs were changed and supposedly all wiring is good. I have tested the truck and only code is the Cylinder Contribution code for #8. The Cylinder Change in Rotational Velocity also shows 0 to less than 1 for all cylinders except about 5 for #8. The AE injector in number 8 is recommended for these trucks, the buzz test sound the same to me for all cylinders before 7&8 were totally different. I have purchased an AD injector to put in number 8 but I don't think that will solve the big problem, it may get rid of the code for number 8. The check engine light is not on and the code related to Cylinder 8 may be normal since the difference between the AE and AD injectors. Without the load on the truck it seems to be running OK, going to put the cab back on and run it for some miles. Trying to see what is going on, need a reliable truck, the rough running was really bad and again seem to come on after running some miles with a heavy load. These injectors are totally rebuilt and are tested by the shop but again don't know if some of the issues would show up under such tests. Right now leaning toward buying all new injectors and having all replaced, unfortunately nothing is returnable even though they have warranty. Trying to see how we can nail this down and figure out what is going on. I have purchased the computer system for testing the truck so can look at most data. Don't understand why there is no miss fire count for any of the cylinders even when the truck is running like crap. Any ideas is appreciated.
Don
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