7.3 won't start when hot - Diesel Forum - TheDieselStop.com
Power Strokes 1994-1997 General Technical discussion of topics related to vehicles powered by the Power Stroke engine in 1994 through 1997 models.

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post #1 of 8 (permalink) Old 11-09-2008, 07:28 PM Thread Starter
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7.3 won't start when hot

hey there, can anyone help me here? I have a 96 7.3 that will not start when hot but it will fire right up if you compression start it
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post #2 of 8 (permalink) Old 11-09-2008, 08:40 PM
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I had same problem, ended up replacing the IPR. Also had to clean the chip and PCM service port contacts where the chip plugs in.

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post #3 of 8 (permalink) Old 11-09-2008, 09:54 PM
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No start when hot is usually an indication of bad IPR (injection pressure regulator) o-rings. You can try that first as it is a lot cheaper than replacing the entire IPR. Here's the part number:

IPR O-Ring Kit (for when IPR valve replacement is not required)
(Ford) F6TZ-9C977-AA
(International) 1825806C92


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post #4 of 8 (permalink) Old 11-09-2008, 10:58 PM Thread Starter
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thanks for the info. however the fact that it will bump start right away when hot tells me it is still getting fuel. I'm lost here.... why would it still bump start if the o rings are bad?
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post #5 of 8 (permalink) Old 11-09-2008, 11:20 PM
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The pcm needs to see 500 psi on the icp sensor before it will fire the injectors. If the ipr is faulty or the ipr 0-rings, or other items related to the high pressure oil system are faulty it might not be able to build adequate pressure from the rpms generated by the starter motor alone.
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post #6 of 8 (permalink) Old 11-10-2008, 07:48 AM
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That definitely sounds like the ipr o-ring issue. My son's 95 had the "won't start when hot" issue. I searched and searched the internet and everything pointed to IPR orings. I told him what it could be but he just had to take to a diesel performance shop. Keep in mind that my kid wants to be a diesel mechanic (he's 17). The owner of this shop hooked it up to his laptop and read a bunch of values and deetermined that the IDM was bad. So, by then the truck was already cooled off, so my son drove it home and commenced to switching IDMs from my 96. Meanwhile, I already called International and had the IPR reseal kit (large o-ring, small o-ring, split o-ring, spacer and nut) waiting on me. I got home and low and behold the 96 IDM had the same result. I handed him the kit, he pulled the IPR out and the small o-ring was split. Cleaned it all up, installed the kit and now she starts every time.
This is my first stop for anything related with any of my trucks. Take the majority consensus and it is usually right.
Just goes to show you that this forum has more knowledge than many believe.

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post #7 of 8 (permalink) Old 11-14-2008, 08:32 AM Thread Starter
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Thanks For The Info On The O Rings. I Pulled It Apart And Found That 1/4 Of The O Ring Was Missing. I Will Be Putting It Back Together Today, Hope That Fixed The Problem. Note To Anyone Who Tries This.... Make Sure You Remove The Entire Fuel Filter Assembly Or You Will Never Get The 1-1/8 Socket On The (ipr) Yes, I Found Out The Hard Way!
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post #8 of 8 (permalink) Old 11-14-2008, 09:43 AM
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I think you could use a wrench too. I did mine about a year ago and seems like that was how got it off. I ended up having to replace my entire ipr and I got a new one through blue ridge diesel which was about $100 cheaper than ford or ih. Even though my truck did run better afterwards, that did not fix my problem though as I tested further and found I had an injector o-ring blown out that I had to replace. Just for anyone else who has to go that route.

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Last edited by sdan27; 11-14-2008 at 09:46 AM.
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