[gchavez]

Hello, I recently purchased AE Scan Tool to help keep my Fords in proper working order. I have been learning a little bit each day. One thing that can help me understand is by learning what exactly happens during the cylinder contribution test. I presume that each injector is measured somehow but I am not sure what is happening exactly.

Can someone explain what is happening when the AE runs a contribution test?

Thanks for taking the time to explain things to a learner.

EDIT: I forgot to mention. I am attempting to run the contribution test on a 7.3 liter PowerStroke.

Thanks.

[ChuckD]

The PCM will shut off each injector in order and adjusts fuel delivery from the remaining injectors as it attempts to maintain engine RPM. 97 and older engines miss during this test, 98.5 and newer do not.

[907DAVE]

In the OBS the PCM will kill injectors, one by one, and measure the percent of RPM drop for each cylinder and compare. Basically if they are all contributing equally the RPM drop for each will be the same.

Dont know how the SD does it, but it sure doesn't feel like it's cutting fuel injectors, wish I knew thought.

[gchavez]

Thank you for the information. I was under the belief that the IDM in '99 and later PowerStrokes is not able to cut out specific injectors. Is this correct?

If the IDM can cut out injectors individually, then wouldn't the AE software have some way for the user to turn specific injectors off and on?

Thanks again for the comments. They are very helpful.

[gchavez]

Originally Posted by 907dave

In the OBS the PCM will kill injectors, one by one, and measure the percent of RPM drop for each cylinder and compare. Basically if they are all contributing equally the RPM drop for each will be the same.

Dont know how the SD does it, but it sure doesn't feel like it's cutting fuel injectors, wish I knew thought.

For the last couple of weeks I have been giving this issue some thought and I am convinced that the CCT in SD trucks is nothing more than the software looking at the Cylinder Rotational Velocities and giving back some sort of result.

The KOER on demand test seems to give things a work out though....I like that one.

[ChuckD]

Originally Posted by gchavez

For the last couple of weeks I have been giving this issue some thought and I am convinced that the CCT in SD trucks is nothing more than the software looking at the Cylinder Rotational Velocities and giving back some sort of result.

The KOER on demand test seems to give things a work out though....I like that one.

Thats PERDEL

[bud48fla]

On a 97' 7.3 is the cylinder contribution test, testing 1-2-3-4-5-6-7-8 in that order or firing order?

[907DAVE]

The "Buzz Test" will fire the injectors (solenoids) all at once, then fire cylinders 1-8 in order.

[bud48fla]

Thanks. I new the buzz test buzzed all at once, then 1-8 in that order. What I needed to know was the cylinder contribution test, does it do the cylinders in firing order?

[907DAVE]

Not sure.........why do you ask?