The 7.3 IPR valve — Injection Pressure Regulator sensor — works together with the high pressure oil pump to "create" oil pressure.
Your 7.3 Powerstroke HPOP provides the oil volume and the 7.3 IPR actually physically "plunges" and produces the psi — pressure.
The ICP - Injection Control Pressure sensor sends the current pressure reading to the PCM which in turn signals the 7.3 IPR to add or reduce pressure.
Ideally, the four of them provide enough oil pressure to the injectors so that when you press on the accelerator, your injectors actuate and your diesel engine gets fuel and the cylinders fire.
So just where is the IP valve located on a 7.3 powerstroke anyway?
Your 7.3 Powerstroke's IPR is located in the center of the engine compartment, screwed into the lower right rear of your high pressure oil pump—HPOP. And the 7.3 HPOP is located under the fuel filter housing.
Here's a detailed diagram of all the parts on a 7.3 Injection pressure regulator.
Is a thin sheet metal retaining nut designed to hold the 7.3 Injection Pressure Regulator solenoid in Place. The Tinnerman, or "tin nut" as it's commonly called, is a 1/2" x 20 fine threaded nut.
Allows the IPR to have its required length. Holds the solenoid in place.
When the IPR is screwed into the HPOP this forms the seal between the 7.3 IPR and the 7.3 HPOP. NOTE: This is a 7.3 Common Leak Location and one of the first places to check if your 7.3 HPOP is leaking.
Seals the IPR valve body to the oil channel, holding the pressure in the HPOP.
Helps Seal in IPR valve body created HPOP oil pressure.
In short, the 7.3 Powerstroke Injection Pressure Regulator controls the high-pressure oil pump’s outlet pressure. It's a valve that interprets electrical signals from the PCM and turns them into actual physical hydraulic pressure in the 7.3 diesel's high-pressure HEUI oil system.
This then operates the fuel injectors. The amount of pressure is controlled by the ICP - Injection Control Pressure sensor and the PCM - Powertrain Control Module - varying ICP pressure by adjusting the IPR duty cycle—add pressure or dump pressure.
So, even simpler... And believe me I've had a tough time understanding it until I boiled it down for myself:
Here's a great video that explains the function of the 7.3 Powerstroke IPR and its relationship to the ICP and PCM (ECM).
Careful though, many 7.3 Powerstroke IPR symptoms cause the same bad behavior in your diesel as a failing ICP, a leaking 7.3 HPOP, bad valve cover harnesses and even a bad IPR or ICP pigtail.
Your 7.3 diesel will start sometimes and not others. When your truck does start, you'll be able to rev the engine and then idle okay for a few minutes. Then your 7.3 diesel engine will start idling roughly and then it'll shut off with no warning.
Your 7.3 Powerstroke won't sputter to a stop, it'll just shut down and won't start again unless you apply a lot of throttle. Once your engine does restart, it'll run and then idle until it shuts down.
Yet another specific symptom is a result of the Tinnerman nut coming loose. If that happens the spacer and 7.3 IPR Solenoid will come off and your diesel engine will die.
If your 7.3 Powerstroke engine has any of the above-mentioned symptoms, you'll need a way to troubleshoot it.
Obviously, a visual inspection of the 7.3 IPR where it screws into the HPOP would be in order. Check to make sure no oil is seeping from around the IPR, signaling that your 7.3's IPR o-ring may have failed.
If you have a basic scan tool that will check the ICP pressure when you are starting your engine, make sure it generates the minimum pressure—500psi. If not, your problem is in your high pressure oil system.
You can also remove the HPOP Reservoir inspection plug/fill port and check the oil level. If the oil is close to the top, the problem could be a bad or failing 7.3 IPR.
There's a handy tool you can use to check if your 7.3 IPR is bad or if it's another component in your 7.3 HPOP or high pressure oil delivery system. However, it's geared more toward professional mechanics than us driveway guys and by the time you pay for it, you could get a new IPR and test to see if it was the culprit.
When there's no signal from the ICP - Injection Control Pressure sensor - the PCM will use a default signal. So if you're experiencing rough idle or no start conditions, try unplugging the IPC sensor harness. If your diesel engine starts and/or the idle gets better, your problem's most likely a bad ICP sensor not your 7.3 IPR valve.
1 1/8" or 29mm extended deep well socket (a standard 3" extended won't clear the end of the IPR valve)
After you reseal or rebuild your 7.3 IPR, you'll want to reverse the above procedure to put it back into your HPOP.
A 7.3 IPR rebuild kit is pretty simple. You get a new Tinnerman nut, IPR spacer, and o-rings to reseal both the 7.3 IPR valve itself as well as an o-ring to reseal the IPR to the HPOP.
Here's the one I used from Amazon - 7.3 IPR rebuild kit.
Pay particular attention to the direction of the tiny pin at timecode 7:56 - The small end of the pin should point toward the HPOP in reassembly.
Technically it's called a 7.3 IPR VGT Solenoid Connector Pigtail. And it's a 2-prong electrical connector with a wire retaining bail to keep it affixed to the IPR connector.
7.3 IPR Part Numbers by model year:
IPR 7.3 Part numbers for model years 1998.5-2003.5 - Engine Serial Numbers - 661,496 to 2,030,402 (f81Z-9C968-AB, CM5013)
1996-1998.5 - Engine Serial Numbers - 187,100 to 661,495 (2C3Z-9C968-BA, CM-5112)1
1994-1996 - Engine Serial Numbers - 501 to 187,099 (F81Z-9C968-AB, CM-5013)
Injection Pressure Regulator - 47 Nm (35 - 37 lb/ft).
Injection Pressure Regullator solenoid tin nut - 6 Nm (53 lb/in)