For common rail diesel engines you can use a solvent that recommended by manufacturer and directly connect it to the high pressure diesel pump and run the engine for 45 -60 minutes
First check fuel pressure with a gauge. There is a valve on fuel rail. If check engine light is on have codes read since engine is managed by many sensors. Start there.
Usually white smoke is the result of a cold engine. After the engine warms up, the white smoke should disappear. Faulty injector spray patterns are another common problem.
It is up in the driver's side frame rail behind the cab, close to were the transmission cross member bolts to the frame. You will have to slide up under the truck and look up in the frame rail to see it.
The amount of gas it takes to start up a pickup truck depends on what type of truck and its engine. The amount used to start up the engine is not significant.
To maintain fuel pressure at the fuel rail, for fast start up.
If you will look at the back of the engine on the driverside between the firewall and driver side head, where the intake and head goes together, you will see 2 silver medal lines coming up from the back of engine side by side and going up to the center of the intake. That is called the fuel rail.
It is up in the driver side frame rail back where the transmission crossmember is.
The filter is located in the frame rail
engine will idle high at start up same as a gas engine will. contrary to what most say, the newer diesels have same application on them as a choke. once engine has warmed up it will idle normally
if you have efi engine take the rails apart and clean the whole system it got wet and radiator fluid has some light oil
it will be your valve lifters common problem for the Mazda 626 engine when they start to get up in the milage