IPR Signal question - Diesel Forum

Tim the 2Lman · 10-25-2009, 11:58 PM

Have a 94 DI that I picked up a few weeks ago. I have crank no start issue and had a question about the signal wave form going to the IPR. Does anyone know what the signal looks like with KOEO? I found an old thread on here that shows a 400hz sawtooth wave form going from 12vdc to ground. I watched mine on an oscilloscope today and noticed that my truck's signal is indeed a 400hz sawtooth wave but it only goes from 12vdc to about 6vdc. I'm not seeing sufficient oil pressure for the truck to enable the injectors. During cranking, the hpop is only producing aroung 400psi. I manually applied 12vdc and ground to the IPR and cranked it and almost imeditately saw 3000psi+ of oil pressure. This tells me that the hpop is probably not the problem. I have run continuity tests between the ECM and the IPR and it shows to have no resistance as it should. Any DI experts out there that are willing to give me some insight? I sure would appreciate it. It has a new IPR and I've tried two ECM's with the same result. Also had the IDM tested and watched it work perfectly in another truck.

**woodnthings8** · 10-26-2009, 09:16 AM

Is this the article you read? ECSD - Injection Pressure Regulator (IPR) - 1994-1997 Power Stroke FAQ

Tim the 2Lman · 10-26-2009, 09:39 AM

Yup. That would be it.

**woodnthings8** · 10-26-2009, 09:40 AM

Thought so, from your description.

Tim the 2Lman · 10-26-2009, 12:06 PM

The picture and the description don't actually say that the signal is 0-12vdc. I'm just concluding that myself. I was just curious if anyone knew for certain or if they had the equipment to look at it and let me know.

**action4478** · 10-26-2009, 12:41 PM

If you grounded the IPR & measured the pressure on a scan , it would see those pressures (full ground = 100duty cycle ) , actually 50-60 IPRDC% is about all you would see fully closed . You may need to check head pressures (isolated )with a gauge to see if you have an injector o ring issue ...

The 3000 psi is what the PCM expected to see full ground..

Have you tried unplugging the ICP connector & trying to start it ?..

Tim the 2Lman · 10-26-2009, 06:54 PM

Yeah. The pressures I'm giving on this post is dead headed. Passenger side line is plugged and the driver's side is plugged into a gauge. Did that to eliminate leaking o-rings as a potential cause.

**action4478** · 10-26-2009, 07:35 PM

Do both sides ....Block both for the IPR...

Tim the 2Lman · 10-26-2009, 10:07 PM

I did. Both are plugged off. One with a plug the other with the gauge. Neither line is connected to the heads.

**action4478** · 10-27-2009, 09:25 AM

With the HPOP dead headed , you are only getting 400 psi?...

Tim the 2Lman · 10-27-2009, 09:39 AM

With the signal as I've described from the ECM/PCM, yes about 400psi. If I operate the IPR simulating 100% then I get over 3000psi. That's why i'm trying to figure out what the signal should look like. If the signal is normal, then I would have to conclude that the hpop is weak. If the signal is not right (i.e. maybe it should go between 0-12vdc instead of 6-12vdc) then I need to be looking elsewhere. The wiring under the hood and under the dash has had some butching done to it so I don't want to rush off and spend big $$ on hpop and that not be the problem. There is only about 100-150psi difference between having the ipr plugged in and not having it plugged in. Hope this helps. Thanks

**action4478** · 10-27-2009, 10:03 AM

You did say the IPR was new .. Did you replace the magnet as well ?...

**action4478** · 10-27-2009, 12:33 PM

This may help also
Testing values for ICP sensor

You need a minimum of .83v for starting (that would be about 500 psi). At key on, you should get a .25v to .4v signal. Operational range for the sensor is .65v to 3.25v. Some approximate pressures compared to voltage signal would be:
500psi = about .85-.87v
1000psi = about 1.4v
1800psi = about 2.3v
2400psi = about 3v
3000psi = about 3.8v
If you hold the ICP connector looking into it with the latch on top, the left pin is Vref, center is ICP signal, and right is Signal return. The corresponding wire colors should be brown/white, dark blue/light green, and grey/red.

Tim the 2Lman · 10-27-2009, 12:52 PM

The ICP seems to follow suit with the pressure gauge. Beings I didn't know if I could trust the ICP and I wanted to make sure that injector orings weren't part of the problem, I bought a 0-4000psi oil filled gauge to install in place of on of the heads and a plug for the other. Yes the IPR is new and so is the coil. Both IPR's give me the same results.

**action4478** · 10-27-2009, 01:17 PM

What is confusing is the ICP of 3000 when not commanded by the PCM ..The pump is working in order to get that much pressure on the gauge. The ICP sensor reports to the PCM what it is seeing & the PCM adjusts IPR as needed , may be a biased ICP sensor ..

Did you try unplugging it yet ?..