Power Stroke Cold Starts

Frequently Asked Questions - 6.0-L and 7.3-L Power Stroke Cold Starts

Here are some answers to frequently-asked questions on HEUI fuel injection, fuel injector stiction and its causes, spool valves, Power Stroke performance injectors, Ford Power Stroke injector systems, and resulting high oil pressure problems, and more.

  1. Q. What is a HEUI fuel injection system?
  2. A. "HEUI" stands for Hydraulic Electric Unit Injector. It is a fuel injection method that uses the oil in the motor to pressurize the fuel inside the fuel injector by means of a separate high-pressure oil pump within the engine. This high-pressure oil pump outputs 500-4000 psi of oil pressure into the fuel injectors. It puts huge stress on any motor oil (whether it's synthetic or conventional), it doesn't matter.
  3. Q. What are the symptoms of fuel injector stiction?
  4. A. Fuel injection stiction most commonly occurs when a cold engine is started. Symptoms appear worse as the weather gets colder. On start-up, uneven engine idling, cylinder misfiring, and an engine non-responsive to acceleration are most recognizable. However, fuel injector stiction symptoms, including cylinder misfires, can continue even after engine warm-up.
Cold Ford truck with engine stiction issues
  1. Q. What is fuel injector stiction?
  2. A. Basically, stiction is the inability of the highly pressurized motor oil to flow correctly through the spool valves, which regulate the oil pressure in and out of the fuel injector's high-pressure oil circuitry. The spool valves are controlled by two 48-V coils inside the injector and move side-to-side and back-and-forth. When functioning properly, fuel is pushed to the cylinders (ON) and back to the crankcase (OFF). When the spool valves encounter friction or "stick," "fuel injector stiction" results.
  3. Q. What causes the spool valves to stick?
  4. A. The movement of properly functioning spool valves is minimal, for example, in a 6.0-L Power Stroke engine, the spool valves move only 0.43 mm in their side-to-side, back-and-forth motion. Thus, even the slightest hindrance, caused by wear on the spool valves and/or engine oil contaminates within the spool valve bore or orifice, greatly affect their proper function, or, causes them to 'stick.'
  5. Q. Can stiction be fixed? What is the best way to fix stiction? Are there added benefits?
  6. A. Although it is important for Powerstroke diesel owners to adhere to a strict maintenance schedule, with oil changes at no more than every 5,000 mile intervals with a good diesel-rated motor oil, it is not enough in most cases. Especially with the 6.0-L and 7.3-L Power Stroke engines, even use of the thinner-grade synthetic 5W40 motor oil is not sufficient. A proven method to fix stiction is use of Archoil's AR9100 motor oil additive, and yes, there are added benefits:
  • Very severely worn spool valves or injectors that have a worn fuel delivery pintle on the fuel side of the injector will usually require injector replacement, but before this costly step, try adding 16 oz of AR9100 into your Power Stroke's motor oil; not only does it have a high success rate (>90%) for solving stiction problems, it contributes much more to the efficient function of your engine. AR9100 cleans and frees contaminated or worn injector spool valves. In most cases injector stiction symptoms completely disappear, even at −20°F. This can happen nearly immediately after adding AR9100 or very shortly thereafter. As such, better performance is noticed quickly, but other positive effects can be observed over the life of your engine.
  • The high pressure of the oil will shear 40W down to 30W as it moves through the injectors. As the injectors shear the viscosity index polymers, the extra protection of a 40W grade oil in high-load conditions is lost. AR9100 compensates for this with its added anti-wear and load protection qualities.
  • The anti-wear and load protection qualities of AR9100 make cold starts quiet and smooth, and the engine runs very smooth and much quieter; driving down the highway you might notice that the engine sounds like a gas engine, the difference is that dramatic. To maintain these results, use AR9100 at every oil drain.
  • AR9100 is the extra additive package that makes HEUI-powered Power Stroke engines perform like they should. AR9100 enables smooth-running, quicker turbo spool-up, excellent injector and high-pressure oil pump performance, and excellent overall engine protection and performance. Don't run your Power Stroke without it.

With thanks to Harry Johnson

Mercedes Benz USA master certified diagnostic technician

ASE master and L1 certified advanced engine performance specialist

WA State certified diesel emission specialist

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