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Discussion Starter · #1 ·
2003 7.3 300,000 miles
Dies when warm and won’t restart until it sits a bit.
I have so far changed cps with my spare Ford oem one. No change
I have unplugged icp pigtail when it would only crank. No change I swapped icp with a known good on other 7.3 - no change
My auto enguinuity numbers are as follows
When running at idle-icp volts-.82/ icp duty cycle 9.37/icp psi 480-500 /
At 2000 rpm as follows-icp volts1.6/ icp duty cycle 19.92/ icp psi 1160
And when it dies and won’t restart the numbers are rpm 180/icp volts .42 /icp duty cycle 64.84/icp psi 150
Tin nut on ipr is tight and the wire connector appears solid. I’m lost as to my next move.??? And help is appreciated thanks in advance
 

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ICP is too low in the last set of numbers (I assume that is cranking when the engine won't start). The IPR solenoid is sometimes known to not work so well when it is hot. The next time it dies or does not start, pour some water on the IPR solenoid to cool it off, then try to start the engine. If it starts, you've found your problem. The engine is not starting due to low pressure in the high pressure oil system. It is also possible that you have one or more injector o-rings leaking by (oil pressure stays higher when cold since the oil is thicker and less likely to leak past an o-ring). Have the o-rings ever been replaced or have they been in there for 300,000 miles?
 

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Discussion Starter · #3 ·
The orings have been in the truck since I bought it with 124,000 miles. HPOP was rebuilt at that same mileage due to a leak when I bought . To clarify for my understanding ... the ipr could be sticking open and not able to build pressure ??
I will try the water /cooling trick and dial into the ipr a bit better..
Is there no other test for the ipr itself ? Thanks for your help .
 

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The orings have been in the truck since I bought it with 124,000 miles. HPOP was rebuilt at that same mileage due to a leak when I bought . To clarify for my understanding ... the ipr could be sticking open and not able to build pressure ??
I will try the water /cooling trick and dial into the ipr a bit better..
Is there no other test for the ipr itself ? Thanks for your help .
When the IPR solenoid stops working the regulated IP hoes to it's default, zero psi and the injectors stop working and engine shuts down. The IPR valve itself rarely goes bad, but the electrical solenoid on it working cold but shutting the engine down hot is common on a IPR with some age and miles on it, it's a hot spot for an electric magnet to last. One can often just change the solenoid, however I don't know of a place that sells just the solenoid solo, so one has to buy the entire IPR assembly to get a solenoid, get an OEM quality part, usually from 140 to 160 bucks. Changing a solenoid only takes me about 15 minutes, changing an IPR assembly an hour, because there is more cleaning up oil that comes out and care to take not getting dirt in the open orifice.
 

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The IPR is normally open to dump pressure. When the solenoid energizes, it closes the IPR so that pressure can build. If the solenoid fails or is weak, the IPR remains open and the pressure stays low. Duty cycle ranges from 0% to 65%. 65% indicates that the PCM is trying to keep the IPR closed longer so that pressure can rise. If the IPR is not responding, I would expect to see maximum duty cycle (which is what you are seeing while cranking) and very low pressure (also what you are seeing while cranking). Since your engine starts fine when it is cold and the IPR regulates pressure correctly under those conditions but not while hot, that is what leads me to think your solenoid is failing.

Resistance in an electrical conductor increases as temperature rises. This causes current flow to drop. Since the IPR solenoid is nothing more than a coil of wire, the increased temperature under the hood when the engine is hot (or natural temperature rise in the coil from carrying current) is causing increased resistance in the IPR solenoid coil. This causes the current flow to drop which weakens the magnetic field generated by the solenoid. The magnetic field is what moves the plunger in the IPR, so a weak magnetic field means there is insufficient force to move the plunger, so the IPR remains open and dumps oil which causes the loss of pressure.

There are not really many tests you can do on the IPR. Duty cycle and pressure and indications of IPR operation or failure to respond when commanded. The water trick that I mentioned is the easiest way to determine if heat is affecting operation of the IPR.

Duty cycle while cranking should stay down around 20% and pressure should be about 500 psig. The idle and 2000 rpm numbers you listed for a cold engine look fine. Your hot cranking numbers are definitely way off.

Here's a link to more IPR information. It talks about testing the IPR, but the tests are limited to monitoring ICP & duty cycle and ensuring that the HPOP reservoir has oil in it.
7.3 IPR Valve / Sensor – Injection Pressure Regulator | Dead Head Diesel

As mentioned by Oneof6, you could just buy a new IPR and install the solenoid on your existing IPR since mechanical function of the valve seems fine. I'm pretty sure you won't be able to buy just the solenoid. Removing the IPR takes an extra deep socket (which you most likely won't find) or a special IPR removal tool due to the stem that sticks out from the valve. If you need to remove the IPR, you can make your own tool pretty cheaply. You'll need a 3/4" drive 1-1/8" shallow socket and a 3/8" drive 9/16" deep socket. Hammer the 9/16" socket into the 3/4" square opening of the 1-1/8" socket. The distortion of the 9/16" socket in the square hole should give plenty of grabbing power to keep it from spinning, so you should not need to weld the two sockets together. Changing just the solenoid is easy - unplug it, remove the tin nut, remove the solenoid, and reverse those steps for the new one.
 

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Discussion Starter · #6 ·
Ok that’s makeing more sense to me now.. thank you
Headed to go get parts and hope. I’ll post back results. Thanks again for your time and knowledge .
 

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Discussion Starter · #7 ·
Changed ipr and ran truck up to temp and more.
For the hot starts icp psi instantly jumps to over 700. The only odd indication is when I removed old ipr approximately two tablespoons of oil came out. I seem to recall on doing hpops prior, when I would not suck out oil, the entire valley would be flooded. Now this was on a cold Motor that has been sitting over night so there may well be some leakage internally in HPOP reservoir . Or is this normal amount for just changing the ipr??
Thanks to greg03 and oneof6 spot on diagnosis .. thanks again work truck is running again
 

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A couple tablespoons of oil when removing the IPR isn't unusual on a cold engine. The IPR discharge is into the front cover and the oil in the HPOP reservoir has to go thru the pump to get to the IPR, and close clearances restrict that.

I'm glad for you that the IPR fixed your issue. I would have suspected injector o-ring leakage. I have experienced that, and barely got home after a stop off on the way. It took a very long time cranking to get it running after that stop. I wound up replacing the injector o-rings after doing some diagnosis.
 
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