We have a bus at work with a t444e 7.3 that won't start when its hot. The only code stored in the ecm is back pressure above/below desired level and a icp pres code. The guys working on it think that replacing the back pressure sensor and the ebpv valve with solve it. I have always heard the bad ipr or injector o-rings cause this,am I right? Btw it is a '96 and has 250K+ on it. This may not be the right place for this but its the same engine as a obs except for the stuff bolted to it.

 

No warm start is usually an IPR o-ring problem.

the EBPV valve wont solve the no-start issue.

Cleaning the EBP tube could help though as well. I doubt the sensor is bad though. The tubes tend to get sooted up.

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Seeing as its giving an ICP code, Unplug the ICP and try starting it. Thats a good way to get the ICP being bad outa the way.
It will default the pressure desired for start.

Though, its probably an IPR problem.

 

Exhaust back pressure would have nothing to do with a no start condition. None. You can completely remove that entire system and the truck will fire.

Need to get it hooked up to some kind of a scanner. Check the ICP pressure and duty cycle while cranking.

Need min of 400psi before the IDM will even fire the injectors.

 

Unplugging the ICP defaults the system to call for 700PSI. (600 or 700, cant rememeber)

 

I understand that, but that will not tell you much.

The correct way to do it is to scan the truck. Rather then start unhooking things...

 

I understand that. I was adding what unhooking it does.

 

Thanks for the info. What about injector o-rings would they do the same thing. I'm somewhat familiar with how these motors work ( I used to have a '96 f250) but I don't get to work on them much as im just preventive maintenance. The guys who do work on them have been gasser mechanics their entire lives and don't understand how a diesel works. Nice guys but they have no understanding on how these operate, just parts changers to be quite honest.