Powerstroke Diesel Injection
Ford 7.3L and 6.0L Powerstroke Diesel engines use a unique injection system that allows for much greater fuel delivery control than sequential injection pump systems and was a forerunner to modern Common-Rail Diesel systems. Unlike Common-Rail, the Powerstroke system uses a common high-pressure oil supply to compress the fuel in each individual injector.
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The 1994-1997 7.3L Powerstroke uses a mechanical lift pump mounted in the engine valley, between the fuel/water separator housing and the turbocharger. This pump delivers low-pressure fuel (roughly 30-80PSI) to fuel galleries in the heads. Excess fuel flows from the fuel galleries to a regulator mounted on the side of the fuel/water separator housing. This regulator allows fuel to flow back into the filter housing, or back to the fuel tank depending on demand. The regulator also contains a small filter that requires regular service. The 1999 and later 7.3L and 6.0L Powerstrokes use a frame-mounted electric lift pump to deliver fuel to the fuel galleries. These galleries have slots open to the fuel injector ports, allowing the low-pressure fuel to enter the fuel injectors. Excess fuel delivered to the fuel galleries by the lift pump is returned to the fuel/water separator housing, where it is either returned to the fuel galleries or to the fuel tank, depending on demand. An in-tank pickup/regulator assembly pre-filters the fuel before being drawn out of the tank and regulates the fuel pressure by restricting return fuel flow back into the tank. The pre-filters in the pickup assembly can become clogged, and require regular service which usually requires removal of the fuel tank.
Injection Control Pressure System
The Injection Control Pressure System is the high-pressure oil system that does the work of compressing the fuel inside each fuel injector. A mechanical high-pressure oil pump is driven by the camshaft and delivers high-pressure oil to oil galleries in each of the cylinder heads. The oil galleries are above the fuel galleries, as this oil enters the top of the fuel injector through passages in the injector ports. The pressure of this oil varies greatly based on demand and can range between approximately 500PSI at startup to about 2,000PSI at wide open throttle in neutral. Injection Control Pressure can be higher during acceleration under load. The ICP system uses an Injection Pressure Regulator (IPR) to regulate the pressure generated by the high-pressure oil pump, and an Injection Control Pressure (ICP) Sensor to monitor it.
Fuel Injector Operation
The fuel injectors in a Powerstroke are part electronic fuel injector, part injection pump. The high-pressure oil supplied to the top of the injector is used to compress the low-pressure fuel supplied to the bottom of the injector. This occurs when the Injector Driver Module (IDM) applies an electrical current to one of two solenoids located on top of the injector. One solenoid is for low-volume, while the other is for high volume, and are actuated according to fuel demand, as determined by the Powertrain Control Module (PCM). While most gasoline engines have injector drivers located within the PCM, the fuel injectors in a Powerstroke require much more power to operate and therefore require a dedicated module which is actually larger than the PCM. When the solenoids in the fuel injector operate, the high-pressure oil is allowed to compress a plunger, which pressurizes the fuel below, opening a check valve in the injector nozzle, and spraying it into the combustion chamber. The PCM uses various sensors, such as Camshaft (CMP) and Crankshaft (CKP) Position Sensors, Boost Pressure (MAP) Sensor, Engine Coolant Temperature (ECT) Sensor, Accelerator Pedal Position (APP) Sensor, and other data to manage injector timing and fuel volume, in much the same way that the PCM in a gasoline-powered vehicle with manages fuel delivery.
Fuel acts as a critical lubricant inside the injectors, and fuel shortages caused by faulty regulators, weak lift pumps, clogged fuel/water separator filters, pickup/regulator filter screens, or running out of fuel, can cause severe injector damage. This means that it is critical that any low-power, smoke, misfire, or check engine light illumination be addressed immediately as these can all be indications of fuel shortages. Another cause of injector damage is fuel quality. It is very important that the fuel/water separator housing be drained of water frequently, as water will cause immediate injector damage. There is also a lot of confusion over the difference between biodiesel and vegetable oil. While processed bio-diesel mixes, available at some gas stations, are acceptable, vegetable oil can cause severe injector damage. The installation of vegetable oil supply systems often requires removal of the fuel/water separator filter and use of a less-effective filter, allowing contaminants and water in the fuel to enter the injectors.
The Ford 7.3L Powerstroke proved to be one of the most reliable engines ever produced. Despite some minor electronics issues with the 7.3L, and some largely owner-neglect or abuse-related issues with the 6.0L, the Ford Powerstroke continues to be one of the most celebrated, longest lasting and dependable power plants on the road. With proper maintenance, these Rob's Powerstroke Performance Center engines can commonly exceed 500,000 miles without requiring major engine repair.