What is HEUI fuel injection? An engine oil

HEUI Fuel Injection
Failure and Solution
The Documented Problem
• Engines prone to stiction issues are the
PowerStroke 7.3 engine from 1994 to 2003,
the 6.0 from 2003 to 2007, the Navistar
T444E and especially the VT365 which was
manufactured from 2003 to 2007.
• Q:What is stiction?
• A:A conjunctive form of Static Friction
• As it relates to injectors, it is simply pistons
which stick in their bore, to a level which
retards the initial movement.
• The 6.0L runs the high pressure engine oil
system much higher than it was in 7.3 L
• “4000 psi” causes shearing of oil polymers
reducing a 15W40 viscosity oil to a 30
weight in as little as 1,000 miles
• Can result in increased exposure to wear
because of reduced lubrication protection
6.0L Facts
• Contains extreme high-pressure engine oil
• High-pressured oil pump is used - HPOP
• Pump used to pressurize the fuel within
the fuel injector for proper atomization and
direct injection into the cylinders
In Summary…
Fuel injector "spool valve" is trying to move back and
forth inside the injector
• In a 6.0L this is achieved with two 48v coils on each end of
the spool valve while trying to overcome anywhere from
500-4000 psi oil pressures being generated
• Spool valve bore needs to be contaminate free and
unrestricted for proper fuel injector operation
• Carbon contaminates, Varnish build up, or Wear will cause
the spool valve to stick, especially when the oil is cold &
thicker and isn't flowing as easily, even with thinner grade
Fuel Management System
There are injector
stiction issues on
Ford 6.0L & 7.3L
PowerStrokes with
the HEUI fuel
injection system.
(Hydraulic Electronic Unit Injection)
What is HEUI fuel injection?
• An engine oil pressurized fuel injection system
• Uses crankcase motor oil to pressurize the fuel inside the
fuel injector via a separate high-pressure oil pump within
the engine.
• High-pressure oil pump puts out anywhere from 5004000psi oil pressure
•Very hard on any motor oil, synthetic or conventional
What are the symptoms of fuel injector stiction?
• Romping uneven engine idle
• Hard starting & Cylinder misfiring
• Unable to accelerate until the engine warms up
• Loss of performance means lower MPG
What causes fuel injector stiction?
An inability for the high-pressurized motor oil to flow
correctly through the fuel injector
1. "stiction" comes from sticking spool valves inside the fuel
injector’s high-pressure oil circuitry
2. The spool valve allows oil pressure in and out of the fuel injector
3. It is controlled by two 48v coils inside the injector and moves
side to side back and forth.
4. When ON, it allows oil pressure to push the fuel into the
5. When OFF, it bypasses the oil back to the crankcase.
What causes these spool valves to stick?
Worn spool valves and or engine oil contaminates within the
spool valve bore or orifice and varnish build up
• Spool valve only moves 0.43mm in a 6.0L PowerStroke
• Less than a half a millimeter for high-pressurized
motor oil to flow
What can be done about the spool valves sticking?
Add Archoil AR9100 into your motor oil
-This will liquefy all deposits in the fluid system
free up contaminated injector spool valves
-Injector stiction symptoms completely disappear, even at -20F
-Normally happens shortly after application
-If spool valves are severely worn or injectors have worn fuel delivery
pintles or nozzles, it usually indicates injector needs replacing
AR9100 has a high 90%+ success rate, but it also does
much more.
Contributing Technician
Harry Johnson
Mercedes Benz USA master certified
diagnostic technician
ASE master and L1 certified advanced engine
performance specialist
WA State certified diesel emission specialist
For more information go to

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