not always

 

The injector has to be cooled and lubed,too. The bypassing diesel lubricates and cools down the injector. Modern VP pumps and injectors have (like the VW Phaeton) an own cooling circuitry with an own diesel-to-coolant heat exchanger, a seperate coolant pump and a additional front mounted cooler. All to make sure heat is out of the diesel.

Actually the amount of fuel that is pumped is way bigger then injected. But it has to be this way to make sure there is always a sufficient amount of fuel under all conditions of driving.
Smoke is not that cool. It only shows there is a huge amount of useless fuel which could be burned with more air, resulting in morrre powerrrrr

 

me and a buddy decided to plug off the return line on his pulling truck and we ended up blowing apart a brannew berry grant fuel pump