No power at top end if lugged at low end

[kjames]

I have a 1997 Dodge with a Cummins Diesel and a five speed. If I lug the RPMs below 600 RPM, when I let the clutch up, the exhaust will smoke severely until I reach about 1000 RPM. Then between 2000 and 2500 RPM, there is very, very little power and very little smoke at all. If I slip the clutch when taking off (not letting the RPMs drop below normal idle), there will be very little smoke and a lot of power between 2000 and 2500 RPM. The engine did not use to act like this and it has not been tampered with. What is wrong with this engine?

 

[SLang]

What color smoke?



If it's black then your engine is running fine, you just need to change your driving habits. First off you should never "floor" it at RPM's below 1500. This is just a waste and hurting your truck. The exhaust air is not moving fast enough. The cylinders may be overheated and the pyro still shows in the "green". Also below 1500 RPM is way below peak torque (1800-1900 RPM) and really is doing nothing to motivate the truck. Unless you are abusing your truck (drags, pulls, etc. ) then you have no reason to even do this. Try listening to the boost and following it with fuel input.



If the smoke is white and does not go away wwhen your engine is at operating temp then your timing may have slipped. This is a semi-common occurance with the P-pumps.



Scott

 

[Cooker]

I can't help much given your description. I would suggest you check your fuel pressure. Just a thought.



-Ryan

 

[kjames]

The engine is only lugged for one or two seconds to get the truck rolling. The smoke is very black, but the important thing that I want to know is why there is no power above 2000 RPM if it smoked in the beginning, it happens every time. If you take off without any lugging, it runs fine. And has lots of power, it has nothing to do with driving habits because this has just started.

 

[SLang]

How about boost and EGT #'s? This will tell a lot about what's going on.

 

[kjames]

I do not know my EGT numbers or my boost. I bought the gauge a year ago, but have not be able to install it yet.

 

[PHaller]

Is your 97 an EGR equipped model? If so, they are notorious for no power at higher RPM because of intake restriction. I can't answer to no power after lugging though...

-Paul R. Haller-

 

[kjames]

No egr

 

[Steve Roseman]

I know it would be almost impossible to tell, but it almost sounds as if your not getting full throttle movement after lugging it.

Does it get kind of jerky when you lug it? Could it be binding up the linkage somehow? Just a thought. Good Luck!

 

[MY6EATSV8'S]

its the governor. I used to do this on perpose before I figured out how to make it do it right. If you lug it low the gov kicks in to keep it running but it also does somthing to not let the fuel advance. If you let off the gas it again it will act normal.

 

[kjames]

Exactly... does your truck pour out black smoke through the lower half of the rpm range if you lug it for a second to get it rolling? Then, do you have no power or smoke over 2000 rpm unless you let off the throttle a bit. Then you have all your power back? I have not modified the engine and the engine has never acted like this before. Thanks for your help.



~KJames~

 

[Strick-9]

There is something in your pump called a rocker. It moves forward and rides along your camplate when the AFC is forward enough and the governor is allowing it. This rocker also moves upward as RPM increase.



What you describe is a textbook case of the rocker being adjusted too low. See, at LOW rpm the rocker moves forward and goes under the plate before the rpm increase enough to move it upward and onto the plate properly. The rocker is spring loaded to prevent damage in nearly every direction. So basically, it goes under the camplate and wedges as it tries to move upward.



Once you let off the throttle the rocker can return and get unstuck. Then when you get back into the throttle at higher rpm is moves all the way forward onto the camplate as it was designed.



Go to Pier's website and look for the directions for "secret governor level adjustment. "



http://www.piersdiesel.com



Good luck,

Chris

 

[kjames]

Thank you. I appreciate your expertise. I wonder if this repair would be covered under the 100, 000 mile warranty.

 

[Strick-9]

Well, I help when I can.



If you don't feel comfortable making this adjustment, there's something else you can try.



You have obviously loosened the starwheel off quite a bit if you get a ton of smoke at 600 RPM.



If you tighten up on the starwheel a bit, it might cover up this problem. If the AFC can restrict fueling until the RPM comes up then the rocker can't get hung up and you won't have a problem.



Obviously, you'll lose the responsiveness you have now.



Always a trade off!

-Chris

 

[kjames]

I think the right thing to do is adjust the rocker, I just didn't want to brake any seals while I am still under warranty. But I may have to and I don't know if the inj. pump is covered anyway. Thank you, kjames

 

[ADSmith]

Mine did this too, until I ground off the point at the very bottom of the cam plate and just made that part flat. That keeps the rocker from sticking under the point and causing the low power you described. Grinding it off is a whole lot easier than adjusting the rocker, and seems to produce the same results.