Found the below thread on another site, searched here for any reference to "CP3 Timing", and found none. If this is common knowledge already, my apologies for the post... This thread doesn't actually refer to timing the CP3, as there is no way to do that (per DC manual) - but it provides instruction on removing gear lash on the CP3 drive gear. I did this, and the clatter/knock at idle I had is gone, and what I thought was injector rattle at low throttle is greatly diminished (~80%).

http://www.cumminsforum.com/forum/3r...g-results.html

Rather than plagiarize, I figured I'd let the original authors speak for themselves. One of the board members from Wicked Diesels also verifies this action and result in another thread.

 

This isn't skepticism, but I do have a question.

My knowledge of combustion engines is not extensive, but I feel I know more than the average Joe. As I understand it, the engine is making compression nearly 100% of the time, if not continuously, based on different pistons within the engine being in different stages of the combustion stroke. That being said, how in Hades do you align the CP3's compression stroke with the engine's, since based on my theory, it already is?

If I am confused, please tell me. But this just doesn't make sense to me.

 

A 4 stroke engine cylinder only makes power on one stroke. Now, most of the time, cylinders make there compression on different strokes. So in that aspect, yes it is making compression all of the time, but on different cylinders. The strokes sequence goes like this, intake ( suck) ,compression ( squeeze) ,ignition( bang ), exhaust ( blow ) . The names in ( ) made it easy to understand and remember for most! Suck, Squeeze, Bang, Blow

Hope that helps!

 

Yes, that's exactly what I was talking about. But my question still stands.

 

The gear lash would in effect lessen the fuel being moved by the pump, so the pump is not supplying a constant fuel pressure or amount of fuel. You could think of it like an intermittant state of delivery. There is still fuel pressure/delivery but it becomes a bit variable, ie the knock. As the engine moves on a continuous cycle of cylinder fire, this would rotate that lash effect throughout all the cylinders in their firing order. So maybe you rhythm of knock is really about every fourth cylinder firing getting a little less fuel in the combustion cycle. Modding or adjusting the pump to eliminate the lash would take the slight fuel intermittance out of the picture, knock decreased or gone. All diesels have what is perceived as knock normally, but the knock may actually have to do with fuel delivery quantity at combustion. It is much similar to low octane knock in a gasser. Effectively whether it is low octane (gasser) or a momentary decrease in fuel (diesel pump pressure) it affects combustion.

CD

 

I think what he is saying is to get the pump in the middle of some of the compression strokes instead of maybe being in synch with one or more. It is all a harmonics thing. There are good harmonics and bad. Evidently he is claiming that have the engine and the CP3 synched or out of synch can make more or less noise. I would have to say it is "plausable".

 

The noise in question is a metallic ping at the front of the engine , not your typical injection knock. It's caused by backlash in the drive gears, harmonics is a good way to put it. The harmonics of the piston pump get out of time with the harmonics of the engine and cause the gears to get slack between the teeth and then come back together and knock. It works "if that is the problem". It was the problem in my engine and I'm seeing more reports that it has fixed other peoples annoying knocks since I posted that on the other forum.

 

Kry to answer your question in a 360 degree rotation the engine only goes into compression with 3 pistons, and exhaust with the other 3 the vibrations you feel from the engine are caused by the engine having a power stroke(combustion) free wheel then start to slow then another combustion stroke.... if the engine is slowing down or speeding up at a different time in relation to the cp3's compression stroke it can cause the gears to develop slack.

 

What size nut is on the gear? Is it a 1 1/8 or a 1 1/16?????

For some reason, my Floor It Stage II has started to fluctuate the RP and at idle, the truck has a VERY LOUD intermitent rattle, and I can only hit 23K psi at WOT. This is on the second FCA. The first FCA that came with my pump at a surging you could feel and hear in the turbo. This FCA seems not to build enough pressure???

 

...So who else has done this and is happy with the results? Any pictures?

 

This should be covered under warranty, am I right? My cp3 started sounding like a jack hammer a few days ago. I could do the fix myself but i only have 1500 miles on the truck and don't want to break anything in the process. Looks like back to the dealer it goes.

 

the engine is 6 cylinders, the cp3 is 3. so like stated above, there will be different harmonics.