Usually radio playing loud enough to drown out all engine noises but heard a strange noise I hope is normal. Approx 75-80 mph cruising up a slight hill engine made a constant loud knock till I got over the top and started down. If I let off the accel slightly noise gone. Get back into the throttle at that special zone and engine sounds like going to come apart. Seems I went approx 1/4 mile with the constant loud knocking. Only happens in that special RPM range with engine having to strain. Is this normal????http://www.dieselplace.com/forum/images/smilies/confused.gif Only seems to happen on the fwy.
Thanks for the advice.

sure its not 2400+ rpms with the pilot injection shutting off?

sure its not 2400+ rpms with the pilot injection shutting off?
Forgive my ignorance, not sure what that means???

When you get your engine above 2400 RPM (which im sure you have) the engine shuts off the pilot enjection in order to make more power. The purpose of pilot enjection is to make the engine quieter and more effient. When it stops the pilot injection around 2400RPMs it may sound scarry if your not farmilliar with it, but its perfectly normal. Since you were going higher speeds and working the engine harder your RPMs were probably in that range for the engine to shut off the pilot enjection.

When you get your engine above 2400 RPM (which im sure you have) the engine shuts off the pilot enjection in order to make more power. The purpose of pilot enjection is to make the engine quieter and more effient. When it stops the pilot injection around 2400RPMs it may sound scarry if your not farmilliar with it, but its perfectly normal. Since you were going higher speeds and working the engine harder your RPMs were probably in that range for the engine to shut off the pilot enjection.
Thanks for the info. Maybe that is what is happening. Hitting the fwy today, I will check my rpms when this engine knocking occurs. Get back with my results. Hopefully that is all this is.

on mine, it seems to cut off the pilot injector at approx 2700 RPM..

And yes, it greatly increases the noise level of the Diesel

Yeah, I think it is 2700 rpm when the pilot injection turns off.

It gets turned off because beyond 2700 rpm the engine is turning too fast for it to be effective. I think the way it works is it gives a little 'pre-squirt' of fuel at the right time before top dead center before the 'main-squirt' and it quiets the engine down. Once you are beyond 2700 rpm the window of time gets too small for the 'pre-squirt' so it is too hard to coordinate.

Mine does the same thing at about 80 MPH (approx 2500 RPM). Good to hear it is a normal thing. 3500 miles on my truck.

I was getting a faint little occasional knocking, at "special" RPM's too. It really wasn't so RPM dependent as throttle dependent. Kind of just as you barely ease back on the throttle. If you nail it, it doesn't happen.
I'm not too worried about it, but I did just notice it last night.



Gar

I was getting a faint little occasional knocking, at "special" RPM's too. It really wasn't so RPM dependent as throttle dependent. Kind of just as you barely ease back on the throttle. If you nail it, it doesn't happen.
I'm not too worried about it, but I did just notice it last night.
Gar

i believe thats the injectors, if you have the drivers information steering wheel buttons set it to instant fuel economy and youll notice that you get the best fuel mileage when you here that little knock.