The 6.0 Powerstroke engine, like the 7.3 its predecessor, uses Hydraulic Electronic Unit Diesel Injectors (HEUI), which receive energy to open from engine lube oil that’s pressurized by a gear-driven high-pressure pump.
The PCM communicates to the Fuel Injection Control Module (FICM) that it’s time to fire the injector. When that happens, an electrical signal is sent from the FICM to the electrical coils. The signal magnetizes the coils one at a time. Next, the spool valve is pulled to the apply side, and high-pressure oil is allowed to flow past the spool and push on the intensifier piston. Then, the intensifier piston travels down on the fuel plunger, delivering fuel to the nozzle area. The fuel achieves the “crack” pressure, lifting the pintle from its seat and delivering the fuel to the combustion chamber.
When the PCM decides it is time to release the injector, an electrical signal is sent to the magnetic coil, pulling the spool valve in the opposite direction. The spool valve moves to the release side, and the contained high-pressure oil is allowed to flow past the spool upward and exit out of the vent port. The intensifier piston travels upward from spring pressure, allowing the fuel chamber to recharge with fuel for the next injection cycle.
A faulty injector fwill cause the engine to smoke or run rough. Using a scan tool that’s capable of performing a power balance test, you can identify the cylinder with the faulty injector. But considering the amount of work required to disassemble the engine to the point of injector replacement, most technicians will replace all of the injectors at the same time.
When performing this job, remember to perform these important steps at the same time:
The high-pressure oil is delivered to the oil manifold via a standpipe. Each rail has a plug, as well. A common problem is seals that warp under the heat and pressure, leading to a high-pressure oil leak that causes loss of injector control. There are updated plugs and standpipes available, and they should be used when replacing injectors.
Before removing the retaining bolt for the injector, properly release the connector pigtail from the cylinder head using a suitable tool such as the OTC6766.
The bolt that secures the injector hold-down bracket requires a long shank T40. If a short shank T40 is used, the injector solenoids can be damaged. When the injector clamp bolt is loosened, the injector will lift up and be released from the cylinder head. Be very careful not to drop the clamp and bolt into the engine.
Prior to installing the injector, it is critical to remove any oil or debris that may have fallen into the threaded injector clamp hole in the cylinder head. Failure to do so can cause the injector not to be fully seated, which can lead to compression leakage in the fuel system and catastrophic damage.
Once removed, be sure the compression seal on the injector tip comes out with the injector. Also, check for any signs of fuel contamination at the injector fuel inlet screen. If contamination is found, the source must be located or the replacement injectors will be sure to fail.
To install the fuel injector, assemble the clamp and bolt to the injector, being careful to note the orientation notch. Lubricate the O-rings with engine oil, install them in the cylinder head, and torque to specifications.
The last step before installing the valve cover is to snap the PCM injector wiring to the injector pigtails. The pigtail’s plastic lip doesn’t always seat securely. When trying to make the connection, the pigtail may get pushed back into the cylinder head. If you’ve already installed the valve cover, you will now have to remove it again.
Fuel Pressure Regulator Update
To help prevent premature injector failure, an updated spring is available that boosts the fuel pump pressure an additional 10 psi. The added pressure ensures that there is adequate fuel in the injectors at all times. The fuel acts as a cushion for the injector’s internal components. Pockets in the fuel system can cause the injector end to break.
Bleeding and Run In
With the engine back together, the oil and fuel system must be bled before trying to start it back up. Use the starter wiring connector on the passenger-side fender to crank the engine over for one minute with the ignition key off.
Cycle the ignition on and off five times. Each time, allow the fuel pump to run for the full 30 seconds before the PCM turns it off. Now it’s time to start the engine!
It is critical not to rev the engine until all of the remaining air in the oil system is purged. The presence of air can create erratic pressure pulses that damage the screen on the injection pressure regulator (IPR) and contaminate the system.
Allow the engine to idle until it reaches operating temperature. Then take it out for a test drive, being careful not to be hard on the throttle until the truck has driven a couple of miles.