injection pump timing

[BushWakr - RIP]

I would not advance it too much more (if at all) at this point.

You do have a possible issue with the reman nozzles though...

You can actually have a very large variation in pop off pressures, even with brand new ones... . someone once told me that even bosch can have as much as 8 bar variation.

I have not personally tested that theory, but you never know.

If I have any choice I buy new not reman nothing... it never fails that by the time you finish re-fixing, re-moving and re-installing you're further ahead to just go new right off the bat...



It may be a load of bad fuel, it may be a couple of "dribblers" among the injectors as well.

The only thing that really changes when putting the truck in gear is the RPM... on mine it likes to idle around 750 RPM in gear. If it gets a tad hazy, I shift to "N" and it goes away. This is caused by the cylinders cooling down and the raw fuel not being fully burned.

If you advance the timing too much cylinder pressures rise dramatically.

You VE pump is now trying to cram fuel thru a nozzle that is undergoing steep pressure spikes... basically it will (I would think) further stress the pump if pushed too far.

Generally you can run around 17*advance as an upper end with some decent reliability.

I'd run a health double dose of fuel additive designed for detergent, cetane, and lubricity thru it.

You can run Howe's Meaner Power Cleaner, Stanadyne, or Lubrication Engineers thru it.



Bob

 

[jbolt]

Buskwkr wrote:



The only thing that really changes when putting the truck in gear is the RPM... on mine it likes to idle around 750 RPM in gear. If it gets a tad hazy, I shift to "N" and it goes away. This is caused by the cylinders cooling down and the raw fuel not being fully burned.





Hey Bob- My thought on this, especially with the PODs AND the DTT trans, is that while idling in gear the tighter TC puts enough load on the engine to make the governor add a little more fuel thus creating the haze. Pop it in neutral and the load is gone along with the haze.



In gear at idle my EGTs are 400. In nuetral they drop below 300.



Make any sense???



Jay

 

[jaynes]

So i'm not going to advance the pump any further. I think I've done enough already. It's probably not bad fuel, because it's been doing this for over a year. it only smokes when it's in gear (at a stop). So i'm seeing the best advice to be putting it in neutral when I'm at a stop? I can handle that. I will also try some heavy duty additive and see what that does. Thanks!



jaynes

 

[BushWakr - RIP]

Hey Jay, you may have something there... . interesting... .

hmmmmmm... ... ... ... ... ... ... ... .



Curious in Canada... ... eh. .

 

[jaynes]

It's possible!

 

[BushWakr - RIP]

As I think about this a little more, I don't see the governor(s) being a factor.

The reason I say this is because there are two factors that trigger "governing".

One is engine RPM and the other is Load.

On the 'start' cycle the pump begins in "start" mode while supplying it's wide open, max fuel rate. Once the RPM reaches 150-300 RPM that "start" fueling rate/volume drops back to "idle" rate.

If the engine were to have much wider range of RPM change than just "N" RPM to "D" RPM then it may well start to govern itself, but not with such a small variation of 150-200 RPM.

At the "normal" idle range of RPM there is insufficient load or RPM to trigger the governor sytem(s).

To test that all you need to do is put your standard transmission dodge in gear, let out the clutch and apply the brake... . you will eventually stall it out. Now if Load and/or RPM governor systems were in play, you'd see the pump start to uprate its fueling in relation to the load change or RPM change...

Yes/No????



Pastor Bob...

 

[jbolt]

Forget the start cycle. The engine is already running.



In your manual trans scenario the engine stalls because the governor setting (throttle position) cannot overcome the load.



As for the auto trans. Say the idle setting (throttle position /governor spring tension) in neutral (no load) equals 800 rpms. In this state the governor weights and spring are at equilibrium. Drop it in "D" with the brake on (load) the rpm drops to 700. Since the throttle position (idle setting) has not changed the governor weights contract due to the lower rpm, causing the spring to pull the tensioning lever adding more fuel.



Well???



Jay

 

[jaynes]

Well I don't know. I do have an auto transmission though, not standard. I will tell you one thing though, I have tried to put my foot on the gas, just enough to knock up the idle A HAIR, while at a stop light, to see if that cured to smoke problem. Well it didn't. It does seem like it idles a little low while in gear, but I don't have a tack, so I wouldn't know. And if it were the idle problem causing the gov. to over fuel the engine at idle, wouldn't idling it up fix that problem? Becuase it didn't when I tried it!

 

[jbolt]

jaynes- did you apply throttle while in gear or in neutral? In gear upping the idle won't clear the smoke.



Maybe you have an injector that doesn't seat well or the pop-off pressures are wrong? Just guessing here.



Jay

 

[jaynes]

You know Jay, I have no idea. And you're right, it doesn't clear up the smoke if I up the idle while in gear. It was smoking before I replaced the injectors. Thats why I replaced them, thinking that was the problem. That didn't clear up the smoke either. It still does it. Advancing my timing didn't clear up the smoke either. I really have no idea why it still smokes. I'm thinking about taking it back to Cummins to have them look at it. But it's $60/h for labor, and who knows how long it could take them. Would the pop off pressures origionate from a problem with that particular injector at the injection pump?



jaynes