Injection pump timing.......

olypopper · **Posted:** Sun Mar 15, 2015 2:37 am

So, does anyone have any proof that these pumps need to actually be timed when replacing a timing belt?

I have quite a bit of cp3 experience on 5.9 and 6.7 Cummins and no timing is required on those.....and I'm pretty sure no timing is really required on the VM.

I will say that on a few occasions I've had to reposition the pump gear on some cummins due to noisy operation at idle due to internal pump phase being off slightly thus causing some gear train rattle. I just don't see how a common rail pump needs to be timed?

tomasnc · **Posted:** Sun Mar 15, 2015 3:03 am

I am in agreement with you. Getting ready to do the rocker arms . From my readings with the Bosch CRD system and the electronic side of this system. The pump sends high pressure fuel to the the injectors and the computer ECU takes it it from there. The old mechanical injection pumps with a unique line per injector requires timing. IMO, ours does not.

Sent from my iPad using Tapatalk

Billwill · **Posted:** Sun Mar 15, 2015 3:15 am

There have been endless posts on the timing of the CP3 pump and I remember one very intensive discussion where I believe Keith from GDE proved that timing does make a difference....the pump is a three cylinder pump with 120 degrees between pump actions being used on a 4 cylinder engine which has 90 degree cycles...maybe on a six cylinder engine it would make no difference.

You can do a search here on the CP3 timing but the general consensus is that is does no harm to mark the position of the pump.

flman · **Posted:** Sun Mar 15, 2015 8:43 am

The marks are there, but the FSM says it does not need to be timed, as well as VM Motori marine service manual. I have done timing belt change with alignment and with out, it made no difference.

papaindigo · **Posted:** Sun Mar 15, 2015 10:04 am

I have no opinion or facts one way or another but as I understand it the pump only "lines" up with the timing mark every 3 engine revolutions. How much that matters in doing the TB job I have no clue. That said two options 1) manually rotate the engine with the original TB installed until the 3 pins insert with the pump mark lined up (at least I assume that's possible) and go from there or 2) assume the factory did it right so mark (2 marks are good) the pump and adjacent cover and install the new TB with the marks lined up. I did the latter but will not the pump pulley is a bit cranky about getting things lined up, wants to slip 1 tooth width but it is doable.

WWDiesel · **Posted:** Sun Mar 15, 2015 11:51 am

From one of gmtcd's early posts back in 07 it was stated:

Quote:

The CP3 shaft is keyed to the drive gear and indexed such that timing can be set to coordinate the pressure waves of the pumping pulses with injection events *

Its a long read but very informative on the CP3 pump:
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=25047&hilit=CP3+timing+CP3+timing
:roll:

I do find it somewhat strange that when I did the timing belt job two years ago, I found the CP3 witness marks were aligned to the index mark from the factory before I removed the OEM belt. And yes, I know it was the OEM belt as I talked to the previous owner and he bought it new and had the dealer do all the service work. We even looked at the service record to see if they had ever replaced the belt. :roll:

thermorex · **Posted:** Sun Mar 15, 2015 12:16 pm

As Billwill, wwdiesel, Keith, gmctd and others stated, the timing mattersin delivering optimum pressure when the injectors open. Since is not a big deal to time it, I'd advise to time it, it only adds few more minutes in a 4 hours job, why wouldn't you time it?

olypopper · **Posted:** Sun Mar 15, 2015 4:09 pm

Thanks for the link WWDiesel! Good info

CATCRD · **Posted:** Mon Mar 16, 2015 12:28 am

thermorex wrote:

As Billwill, wwdiesel, Keith, gmctd and others stated, the timing mattersin delivering optimum pressure when the injectors open. Since is not a big deal to time it, I'd advise to time it, it only adds few more minutes in a 4 hours job, why wouldn't you time it?

x2

It takes almost no extra time to do it right, so just do it. Mine was timed this way from the factory. I noticed when I changed the belt and put it back how I found it.

gmctd · **Posted:** Mon Mar 16, 2015 3:27 pm

flman wrote:

The marks are there, but the FSM says it does not need to be timed, as well as VM Motori marine service manual. I have done timing belt change with alignment and with out, it made no difference.

FSM intent is to differentiate between CP3 with ECM injection timing off Crank Position Sensor and Cam Position Sensor versus indexed timing-gear position for injection timing of earlier P7800 and VP44 injection pumps

However, if CP3 is not pumping-impulse timed to injection event, can get some noisy response from the rail and injector pipes
- set gear index where you found it if first-time service
- unknown previous repair work, you're on your own, but still must be done

flman · **Posted:** Tue Mar 17, 2015 9:04 am

I am just wondering why when VM puts gears vs timing belt in the same engine for marine duty, they explicitly state, injection pump does not need to be timed, do they use a different CP3 pump? :?:

https://dl.dropboxusercontent.com/u/196 ... _UK_M_.pdf

olypopper · **Posted:** Tue Mar 17, 2015 10:04 am

Since this pump is similar to the pump that supplies fuel to the much larger Cummins and Duramax engines I find it unlikely that a situation could occur in which fuel demand could ever reduce pressure enough to cause problems. This pump is fully capable of 26k psi+ On 8 cylinder engines.

Since this new to me Jeep is not going to be a daily driver for quite some time, I'm actually going to try out "timed" vs non timed and see what the noise differences are.

The marine service manual seems to point towards an outcome of no difference.

gmctd · **Posted:** Tue Mar 17, 2015 10:08 am

flman wrote:

I am just wondering why when VM puts gears vs timing belt in the same engine for marine duty, they explicitly state, injection pump does not need to be timed, do they use a different CP3 pump? :?:

https://dl.dropboxusercontent.com/u/196 ... _UK_M_.pdf

Can't say for sure, that being taken out of context - probability exists that reverse-impulse feedback would not affect geartrain like it would affect flexible timing belt - or customer noise complaints - can you post link to entire manual?

gmctd · **Posted:** Tue Mar 17, 2015 10:31 am

olypopper wrote:

Since this pump is similar to the pump that supplies fuel to the much larger Cummins and Duramax engines I find it unlikely that a situation could occur in which fuel demand could ever reduce pressure enough to cause problems. This pump is fully capable of 26k psi+ On 8 cylinder engines.
Which one of the mentioned engines has a fiber-reinforced rubber timing belt on the CP3 injection pump?
Since this new to me Jeep is not going to be a daily driver for quite some time, I'm actually going to try out "timed" vs non timed and see what the noise differences are.

The marine service manual seems to point towards an outcome of no difference.

thermorex · **Posted:** Tue Mar 17, 2015 10:51 am

My question is still the same: considering the few minutes extra, why would somebody not time it? Regarding why should be timed, the explanations provided here make sense, if the math does not point to them being right is another question, I one would not waste my time to wonder.

flman · **Posted:** Tue Mar 17, 2015 11:01 am

gmctd wrote:

flman wrote:

I am just wondering why when VM puts gears vs timing belt in the same engine for marine duty, they explicitly state, injection pump does not need to be timed, do they use a different CP3 pump? :?:

https://dl.dropboxusercontent.com/u/196 ... _UK_M_.pdf

Can't say for sure, that being taken out of context - probability exists that reverse-impulse feedback would not affect geartrain like it would affect flexible timing belt - or customer noise complaints - can you post link to entire manual?

Here is 3 more pages of no timing on the pump https://dl.dropboxusercontent.com/u/196 ... 010_UK.pdf

Here is the entire manual, thanks to Ranger1 https://dl.dropboxusercontent.com/u/196 ... 0_UK_M.pdf

gmctd · **Posted:** Tue Mar 17, 2015 11:41 am

Thanks - this FSM explains much of the what and wheretofore that occured during executive decisions for our engine

First notable difference is the industrial\marine engine has only one camshaft, located in the engine block, and two pushrod-driven valves per cylinder, with a separate head per cylinder = four (count'em = 4) heads per block

Next is the timing geartrain, and that CP3 appears to have an indexed keyway, specific to a specific timing procedure

Next is the etc, etc, and etc

Not much to compare with or refer to as examples for servicing our version

I would intensely ignore any procedural references contained therein

flman · **Posted:** Tue Mar 17, 2015 4:09 pm

gmctd wrote:

Thanks - this FSM explains much of the what and wheretofore that occured during executive decisions for our engine

First notable difference is the industrial\marine engine has only one camshaft, located in the engine block, and two pushrod-driven valves per cylinder, with a separate head per cylinder = four (count'em = 4) heads per block

Next is the timing geartrain, and that CP3 appears to have an indexed keyway, specific to a specific timing procedure

Next is the etc, etc, and etc

Not much to compare with or refer to as examples for servicing our version

I would intensely ignore any procedural references contained therein

So a little bit of a different animal, I would think it would still want to fire the pump with the same timing as our KJs? I wonder if the pump turns at the same ratio on the KJ and Marine engine?

gmctd · **Posted:** Tue Mar 17, 2015 5:21 pm

You'd need some up-close and in-depth pics of the timing gears, so since that CP3 is driven off the cam gear:
- cam is driven 1/2 crank speed so you'd need crank tooth-count and cam tooth-count
- to get 1:1 crank speed CP3 would require gear with 1/2 timing gear tooth-count to equal number of crank-gear teeth
- and etc to interpolate for various ratios, as necessary to match KJ ratio

FYI: the CUMMINS CP3 is not keyed to the shaft, and replacement involves merely attaching a gear puller to the pump gear with the timing cover still in place, separating the gear from the shaft, inserting new CP3, torquing gear nut to spec, and driving away - no timing, no fuss, no muss

So, obviously, it seems to me, the difference in timing procedures is in the mechanical geared timing-train versus the belted timing-train -
gears can take more backlash than a rubber timing belt, 'n'est ci pa?

WWDiesel · **Posted:** Tue Mar 17, 2015 8:30 pm

I think this may be a bit of a witch hunt? No written evidence to prove it must be done; but some very sound phase angle reasoning and other findings to do it if you so desire.
To each his own, do it if you want to, or not if you do not want to....your choice!

I still find it extremely strange that the gear has a factory alignment dot and a corresponding alignment point if it is was not needed or intended to be used as such! :shock:

Again, mine was aligned from the factory to these two marks before I replaced the belt, so why did they build it that way????
Only VM knows.....

Injection pump timing.......

Who is online