What up with this?

Reply Subscribe

Thread Tools

Search this Thread

Jul 5, 2009 | 05:26 PM

#31

74baja

Elder User

Joined: Oct 2007

Posts: 672

Likes: 0

From: NJ

I have a question. What exactly does a contribution test measure?

Jul 15, 2009 | 04:46 PM

#32

fifthwheel01

Senior User

Joined: Apr 2009

Posts: 395

Likes: 1

From: Texas

the stealerships payroll fund.

Jul 15, 2009 | 04:56 PM

#33

superduty4x4

Hotshot

Joined: Jul 2003

Posts: 12,177

Likes: 40

From: Newport, WA

Quote:

Originally Posted by 74baja

I have a question. What exactly does a contribution test measure?

I don't have a technical explanation, but basically its a test to make sure that each cylinder is contributing equally to the running of the engine. If one cylinder is really high or really low, it indicates a problem on that cylinder.

Jul 15, 2009 | 06:56 PM

#34

Kwikkordead

Fleet Owner

Joined: Jun 2004

Posts: 25,090

Likes: 1,112

From: Rio Rico, AZ.

Quote:

Originally Posted by 74baja

I have a question. What exactly does a contribution test measure?

Quote:

Originally Posted by superduty4x4

I'll explain this in a little more detail.
The cylinder contribution test is a measurement of each cylinders contribution to the running of the engine.
It measures the amount in percentage of rpm drop per cylinder per ignition event.
If all eight are pulling thier weight evenly you will have zero % on each cylinder.
If you have an injector that is going south then will have a percentage reading for that cylinder.
You can start to feel anything above 5% or so.
It starts to rock the engine at around 15%.
I don't know what percentage a dead miss will be, but the momentum of the flywheel will prevent a reading of 100%, but I hope this explanation helps.

Jul 16, 2009 | 12:33 AM

#35

Visseroth

Posting Guru

Joined: Apr 2009

Posts: 2,447

Likes: 1

From: Northern Idaho

Thank you, this is good information. I didn't know what it was so I thought it to be a good question as well.

Jul 16, 2009 | 04:41 PM

#36

MSB6

Thread Starter

Junior User

Joined: Dec 2006

Posts: 54

Likes: 0

What are the symptoms if an injector is starting to go bad? It seems to run good on the highway above 1500 rpm but below that in stop and go traffic, mainly at lower rpms, it feels like a miss. My fuel mileage has dropped 3-4 mpg and it has started using some oil. Approx 3 qts per 5000 miles.

Jul 17, 2009 | 08:48 PM

#37

74baja

Elder User

Joined: Oct 2007

Posts: 672

Likes: 0

From: NJ

Awesome explanation Dan! I totally get it now. So, if one cylinder is not producing as much HP as the average of the others, it will actually slow the engine down, so they can measure the RPM at each ignition to find which cylinder is slowing things down. Cool. I guess it would be good to do this in conjunction with a compression test to make sure that things aren't just weak all around, or to help diagnose why the contribution is off.

Jul 17, 2009 | 11:59 PM

#38

Kwikkordead

Fleet Owner

Joined: Jun 2004

Posts: 25,090

Likes: 1,112

From: Rio Rico, AZ.

Quote:

Originally Posted by 74baja

Awesome explanation Dan! I totally get it now. So, if one cylinder is not producing as much HP as the average of the others, it will actually slow the engine down, so they can measure the RPM at each ignition to find which cylinder is slowing things down. Cool. I guess it would be good to do this in conjunction with a compression test to make sure that things aren't just weak all around, or to help diagnose why the contribution is off.

That's it right there.