Here is a little info on what our trucks use for the control of the fuel system. If anyone else has any good imput it would be great. I myself am fault finding to figure out why I have poor fuel milage, sluggish response, surging after driveing for an hour or more. Hope thi sbit of info may help others.

1. The stock lift pump is suppose to push out at MIN 11.5 PSI. All the books says for the GPH is that the flow is sufficient to supply the injector pump. It draws 5 amps at max flow and is 100% duty cycle.

2. Fuel heater if not wroking properly can cause wax build up (unlikely unless in very extreme cold weather ie -30 cels or below), or may cause blue and or white smoke.If the fuel is below 45 F +/- 8 F the fuel heater will turn on and then turn off once the fuel temp in the element reaches 75 F +/- 8 F. Cold Fuel will cause white smoke. Interesting. I truly wonder what the reflashes are from DC to fix these symptoms. Are all they doing is changing the heaters parameters to preheat the fuel?

3. FCA fuel control actuator. It's job is to control the amount of fuel entering the low pressure side of your injector pump. It is a solnoid operated valve located on the bottom driver side of your pump. The ECM controls the action of this valve. Fully open and it has full fow of fuel into the High pressure side of the pump. closed and it will shut off the fuel supply.. Why is this important? After talking to a few mechanics about some issues one thing that was brought up about the FCA and it having premature wear on it. This casuing it to not work properly. If the ECM is demanding that fuel be stopped and it is getting by the FCA then this is casuing to much fuel to enter the high pressure chambers, this in turn will cause to much fuel to be routed to your injector rail. At the end of the day how does this effect a person. To high of a pressure and the end result is leaking injectors. because the fuel pressure is to great with in the rail system.

4. The over flow valve is another problem area that seems to be casuing a few problems with in some of the newer trucks. If this valve gets dirty and cannot open then fuel pressure cannot bleed off and you will get a pressure spike. Although this is unlikely.
If the opposite happens and the valve will not close properly then you will have a loss of pressure with in the Injector rail system. this in turn will result in poor fuel economy, loss of power and also a incomplete burn as the injectors will not be able to give the proper amount of fuel into the chamber.

5. Next is the Fuel Pressure sensor. It controls when the over flow valve will open and close. both the sensor and the over flow valve are mounted on the fuel rail. If this sensor fails then your truck will go into limp mode or wont run at all. The sensors are pretty reliable but they are the key to the whole system.

6. The fuel filter. Still not sure as to the actual micron it filters down to. I beleive it is 10mic's. A few of the dealerships have stated that injector wear is being casued by poor fuel filtration. Yet non of them have been able to state what level of filtration is needed to keep this wear from happening.( cant blame them neither can DC). One thing I do know is that three out of 4 dealerships said that Shell has the best fuel additive package for Diesel fuel. Since they hve been using them they have noticed a difference in power and economy.
kinda makes a guy wonder if it is the actual dirt in the fuel or if it is the amount of water in the fuel. Water at pressures of 20,000psi can cut steel. So if water does get by the filter system can and is this causing the problems with some of these trucks? Not sure would be good to find out.

Not sure if this helps any one out at all. I have been told to look at the FCA and also over flow valve for signs of wear. If found then bring into the dealership to have them investigate further.

Cheers