Originally Posted by bismic

The 6.0L injectors are totally reliant on two electromagnets to shuttle the spool and control the oil to the injectors. The 7.3`s use an electromagnet also but they also have a spring to return the poppet to the closed position. Obviously the spring will work much better to "cut" through the thick oil and close the oil flow.

The small spool valve in the top of the injector that controls the flow of high oil pressure fed to the intensifier piston in the fuel injector only moves .017", back and forth, on and off every time the injector fires. Many factors play in to how well that valve works such as, oil temp, oil quality, normal wear, ambient temp, and many others. As this valve ages it polishes itself inside the bore of the spool valve and as the spool valve slams back and forth it can set up the condition like a suction cup, hanging the valve to one side or the other. This uncommanded uncontrollable condition is called stiction or also called oil latching. Mostly its a rough run cold condition but in severe cases it can be a no start or pretty harsh misfire condition. Not only will running oil with too thick of a viscosity cause rough starts, but this also will interrupt the shuttle action of the spool causing injection timing to be retarded causing poor performance and decreased mileage until the oil is up to full operating temperature. It can also cause poor combustion and coking in the EGR components and the turbo.

Oil that stays inside the spool valve on a hot engine shutdown and is allowed to cool slowly in the injector can aggravate the condition on restart, so the newest reflash (calibration update to your truck's computer(s) uses inductive heat (remember your FICM is a DC-DC comvertere that steps up your 12V electrical supply to 48V) after shutdown to keep the oil warm, keep its viscosity low, and maximize the oil flowability to purge the oil from them. It has worked very well. It is an excellent preventative measure. The newest flashes addresses improved troubleshooting of FICM and related components, but also include some adjustments to "ease" the electical strain produced on the FICM.