Cylinder Contribution Test - PowerStrokeNation : Ford Powerstroke Diesel Forum
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post #1 of 14 (permalink) Old 11-16-2007, 03:34 AM Thread Starter
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Cylinder Contribution Test

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.

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post #2 of 14 (permalink) Old 11-16-2007, 03:36 AM
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Re: Cylinder Contribution Test

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.

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post #3 of 14 (permalink) Old 11-16-2007, 03:38 AM
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Re: Cylinder Contribution Test

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.
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post #4 of 14 (permalink) Old 11-16-2007, 03:44 AM Thread Starter
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Re: Cylinder Contribution Test

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.

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post #5 of 14 (permalink) Old 11-16-2007, 03:46 AM
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Re: Cylinder Contribution Test

White smoke is indicating unburnt fuel. It's atomized diesel that has not even attempted to ignite.

TAG II, Exhaust Air Guide, K&N FIPK, Hood insulation delete, foil delete, SX and A1000 pumps, door dinger delete, COMPOUND trans coolers and a Banks Stinger+++ with the Banks TransCommand and Chrome curb Feelers.

248.9HP 4ft/lbs @ 3,400 RPM (don't forget to divide by 1,002 and carry the 5).

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post #6 of 14 (permalink) Old 11-16-2007, 03:51 AM
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Re: Cylinder Contribution Test

Yeah I have it too on startup.

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post #7 of 14 (permalink) Old 11-16-2007, 03:54 AM Thread Starter
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Re: Cylinder Contribution Test

Well I guess I can crack open the VC and check it out.

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post #8 of 14 (permalink) Old 11-16-2007, 04:00 AM
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Re: Cylinder Contribution Test

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...

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post #9 of 14 (permalink) Old 11-16-2007, 04:18 AM Thread Starter
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Re: Cylinder Contribution Test

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Originally Posted by CSIPSD View Post
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...
No I didn't have an AE, I used my buddies Snap-on scanner. The truck also was not warmed up, I had just started it.

I might run back down to the shop tommorrow and clear codes again the re-do the cylinder test. The truck seems to be running fine however

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post #10 of 14 (permalink) Old 11-16-2007, 04:19 AM
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Re: Cylinder Contribution Test

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Originally Posted by Deputydog View Post
No I didn't have an AE, I used my buddies Snap-on scanner. The truck also was not warmed up, I had just started it.

I might run back down to the shop tommorrow and clear codes again the re-do the cylinder test. The truck seems to be running fine however

Needs to be at operating temp when you run the tests...

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