2004 6.0 will not start hot - Ford Powerstroke Diesel Forum
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Old 04-24-2013, 07:33 AM
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2004 6.0 will not start hot

Hello, I have a 2004 (build date 08/03) 6.0 and I am having hot (warm) start issues. When the engine is up to temp starting is difficult but possible. After running a bit longer it will not start again until it cools down.
4 months ago I did an EGR cooler delete, new oil cooler, new ICP sensor, bluespring fuel pump mod, turbo recondition, cat delete, pink coolant and sinister coolant bypass.
Then truck runs good other than a brief warm up period.
I have read several posts relating to ICP sensors and IPR sensors.
The IPC I replaced during the mod had oil in the connector housing so I decided to replace it at the time. It was replaced 40K miles prior by the dealer.
Both IPR and ICP are located on the HPOP so acess to them will be a joy.
Perhaps removing the degass bottle and FICM?
I also read about unplugging the ICP and see it it starts.
Will this definately confirm a faulty ICP or just fool the FICM via IPR?
If this is doable them would I be OK unplugging it while cool then warm it up and verify that it will start?
Any ideas or troubleshooting clues much appreaciated.
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Old 04-24-2013, 07:41 AM
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no codes or external leaks.
Truck has lost bit of power prior to this also.
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Old 04-24-2013, 10:54 AM
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If the ICP is reporting bad or no signals, then disconnecting it will allow the truck to start, because the ECM will assume the truck is at 500psi and allow it fire off. Your hot, no start is most likely related to a HPO leak or weak HPOP. Read what the ICP and IPR readings are when the engine is cold, as it warms up, and when its at operating temp. I'd almost bet that when its hot the IPR is at 70% or higher and the ICP reading is less than 550psi. Some 03's and 04's had issues with the HPOP discharge tube rubbing the cover and causing leaks. Mine did. If the HPOP hasn't ever been replaced then I would say its starting to fail on you. Heres some good reading on hot, no starts:

No start issue? Look here.
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Old 04-24-2013, 11:44 AM
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I see, so by unplugging the ICP doesn't necessarily prove a bad sensor. Only the likelihood of a pressure loss somewhere within the system.
I did notice a loss of power when towing my camper approx 8000lbs. where it would normally tow in 5th @ 2000 rpm it was having to drop a gear. Would the loss of power be proportional to the oil viscosity? How idle with Diablo tuner diagnositcs shows 641rpm, 100% fuel pump, .97V inj ctrl press, 4.41 MPA inj ctrl press, 1.056mS inj pulse width. I didnt try to read while cranking no do I know if it is possible with this programmer.
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Old 04-24-2013, 11:45 AM
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*hot idle prior to shutting down and attempting to re-start
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Old 04-24-2013, 11:59 AM
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Yours is showing the same signs mine did, pulling a trailer too. It all ended up being a weak HPOP. I dont know if a Diablo will show IPR and ICP readings, but to be 100% sure whats going on, we have to find out what they are.
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Old 04-24-2013, 12:10 PM
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OK Thanks. I looked back on a few pics I took of the live diagnostics both hot and cold.
cold 1.19V ICP volts verses .97 hot
cold 5.56 MPA ICP verses 4.41 hot
1.216mS Inj pulse width verses 1.056mS hot
would all hot readings drop from a lack of oil pressure?
Also I have read conflicting values for ICP pressure required to start. One 600 and the other 800.
Reading the ICP voltage to pressure chart .97 would be borderline low if 600 and too low if 800.
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Old 04-24-2013, 12:32 PM
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OK I just read a chart stating 1.0 Volt/580psi 4 MPA minimum required at engine cranking speed 100 RPM.
With full load pressure signal at 3.22 volts.
I do see the ICP voltage increase as throttle does so it sure points to the HPOP being weak. Suppose weak HPOP pressure would translate in weak injector duty therefore the power loss.
I will take it for a spin and check full range ICP voltage to verify both cold and hot.
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Old 04-24-2013, 03:45 PM
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I don't know much about 6.0s but I had an issue with my one of my 7.3 trucks where it wouldn't start hot. I replaced the injector O-rings and it fixed it.
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Old 04-26-2013, 05:08 PM
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We now know the ICP is reading well, now we need to know what the IPR is cold and hot. On a healthy system the IPR should be around 28% when fully warmed up. Anything say over 35 % when hot is telling you that its having to work harder to try and maintain the desired ICP reading. For instance, an IPR at idle when warm should be around 28%, this will create around 650psi +- 50 at the ICP. If the pressure starts falling from a leak or weak pump, the IPR will try to compensate by closing more to make more pressure. Once the IPR gets to around 85% it basically stays closed trying to create the desired pressure. When our trucks experience this, the pressure will eventually fall off enough to cause the engine to stall, because there's not enough pressure to fire the injectors.
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