7.3L Powerstroke Glossary

CPS – camshaft position sensor

EBPV – exhaust back pressure valve

GPR – glow plug relay, controlled circuit component connects truck battery to energize glow plugs. CA factory emissions has a shunt.

HEUI – hydraulically actuated, electronically controlled, unit injection, fuel system http://www.trucktrend.com/how-to/expert-advice/1304dp-heui-how-high-pressure-oil-injection-systems-work

HPOP – high pressure oil pump

HPOP, part 1:We will begin this series, yes, series because there is way too much to cover in a single post, with a general outline of hydraulic systems and pumps.

There are four different kinds of pumps on the 7.3 engine so we will begin with some generic knowledge. All fluid power is referred to as hydraulics whether the fluid (and believe it or not, air is also called a fluid but we are not including or the turbo here) is water, motor oil, PS fluid or refrigerant.

The water pump is nothing more than a centrifugal impeller pump, probably the simplest type of pump we have on the engine. The impeller spins and forced fluid to the outside where the pressure rises to push fluid through the engine.

The PS pump is a slipper pump, very similar to a vane pump. It works by rotating a round center with slots containing canes or slippers with springs behind them inside of an eccentric housing to build pressure.

The LPOP that sits directly behind the harmonic balancer is a gear rotor pump.

Finally, there are two swash plate pumps on these engines.

One cooks the cab; it is the AC compressor.

The other is the HPOP. A swash plate pump works by rotating a cylinder filled with pistons in a radial circle against a plate with a fixed angle. As the cylinder revolves, the pistons move in a linear motion in and out much like pistons move up and down in the engine. The portion furthest away slows the piston to draw fluid into its cylinder but as it rotates to the portion closest it drives the piston deeper into the cylinder to force the fluid out. The angle of the plate determines how much oil will flow.

Think of it as an engine with a normal crankshaft versus an engine that has been “stroked”. In the stroked engine, the diameter of the cylinder remains the same but the stroke is increased thereby creating a larger engine. With performance HPOPs, they simply change the angle of the plate to “create a larger displacement” pump. It is done by increasing the stroke of the pump.

Credit: Gary McClenny (Facebook Group: 7.3 Powerstroke Technical Page)

ICP – injector control pressure

IPR – injection pressure regulator

Transducer that converts pressure into a linear electrical signal. Pressure of the oil in the rails acts against a diaphragm inside the sensor. That diaphragm has a very strong spring on the opposite side of the diaphragm from the oil that opposes movement. It is precisely calibrated in PSI.

On the “dry side” is an electrical variable capacitor attached to the diaphragm. A variable capacitor is always a 3-wire circuit. In this case, it is a 5 bolt DC circuit that originates in the PCM. IT MUST HAVE a positive and a negative terminal in the PCM. This is only the reference voltage against which we compare the signal voltage.
I have made a drawing of a variable resistor circuit showing the 3 wires. We have what we will call the hot, the ground and the signal.
The signal voltage varies with pressure so our transducer converts variable pressure into variable voltage in proportion to the pressure.
The PCM does not look at or care about actual pressure. It only sees the voltage and used that voltage as an input (along with other inputs) to determine how much output voltage is needed to actuate the IPR to the value required to make the engine produce the power calculated through the compilation of PIDs (parameter IDs) it is looking at.
If the diaphragm ruptures, oil will be present in the connector body on the ICP and may even flood the valley if bad enough. The problem with a leaking or ruptured diaphragm is that the electrical voltage is no longer proportional to the oil pressure because some of the pressure is leaking off.
Another common failure of the ICP is an electrical internal ground that does not allow the signal to return to the PCM. This failure typically shuts the engine down immediately and without warning. The easiest way to check for this issue on a no start condition is to simply unplug the ICP connector. If a faulted ICP is the root cause of the shutdown, the engine will start and run using previously created PIDs held in the KAM (keep alive memory) as long as battery voltage is not interrupted (removing voltage from the KAM will erase the memory as it is simply a RAM system.

Credit: Gary McClenny (Facebook Group: 7.3 Powerstroke Technical Page)

PSD – Powerstroke Diesel, trademark ™️

%d bloggers like this: