in diesel motors what is making that knocking sound and why are the older dodges knocking sound that much louder?

 

Injector pressures are very high, so naturally they are going to make alot of noise when they fire. Some are louder than others depending on the engine.

 

so the dodge has more pressure

 

I doubt it, I don't know about the cummins, esp older ones... But I believe the IDI 6.9/7.3 were around 500 psi max? A PSD goes from (might not be exact on the #'s) 500-21000 psi. I belive alot has to do with how the injector works vs engine design.

 

you are hearing the ignition fire. if that makes sense. ever heard a gasoline engine "deisel" when you shut it off? same principle. you are hearing the diesel fuel explode in the chambers. our injector solonoids are also very noisey. the common rail motors are quieter due to the more efficient injection system.