I just run a little Marvel in mine.

 

Sounds like the CP3 is out of time...

 

There is no specific timing on the CP3 pumps.

 

This may be a long shot, but check the bolts holding the flex plate to the converter. While you're there, inspect it as best you can for cracks. A cracked neck on the converter will also make that noise. Hopefully for your sake it's neither.

"Apparently the CP3 injection pump can be re-timed by moving the position of the gear in relation to the drive gear in the engine and that helps a lot of people get rid of the knock."

^--not so.. If you'll look at your CP3, you'll see that it's belt drive, not gear drive. Timing and duration are controlled by the computer.

 

Please show me this drive belt...I want to see it in the 3rd gen FSM...if one exists, why is there no replacement interval???

The CP3 in the cummins is directly driven by a timing gear by the gear drive on the front of the engine. Mine is, there is no belt.

And while they don't have specifications on timing, they can cause noise if the CP3's drive gear "slaps" the rest of the gear drive. There have been many, including myself, that have had the noise eliminated by retiming the CP3...which involves nothing more than removing its drive gear and reinstalling it at a different clocking. It stems from the pump coming off a pressure stroke with slack in the timing gear assembly.

---AutoMerged DoublePost---



This diagram is directly from the 2004FSM, and although it is low resolution, there is NO belt.

Attach C3428B, or L4407A (or equivalent) gear puller (Fig. 11) to pump drive gear with 2 bolts, and separate gear from pump (a keyway is not used on this particular injection pump). Leave drive gear hanging loose within timing gear cover.

Since the gear has no keyway, this allows the user to have infinite adjustment to that gear. And again, while there is no actual pump timing like the VP44 equipped trucks, the pumps stroke in relation to timing gear slack can, and does, cause a "rapping" noise from the timing gear cover.

 

why do you suggest that one should not use ATF as an additive?

 

The general thought is that ATF is not designed to burn (its a transmission fluid), the newer stuff is partially synthetic (may not burn), and it has friction modifiers (may actually reduce lubrication).

I know a lot of guys swear by it, and have a lot of miles with it. I would have liked to have seen them compare/analyze it during the fuel additive lubricity study.

One additional point is that it might be "worse" in the common rail because of the elevated injection pressures.

 

could b an injector does it hard start