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Discussion Starter #1
School me about it . I thought that as load goes up ( throttle input) the duty cycle would go up ? I'm getting a maximum of 39% at full throttle at 4th gear at 3300rpm . School me please .


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You need to monitor your icp also. But if your icp is at the desired pressure the ipr won't get any higher.
 

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Discussion Starter #3
The icp was pretty steady at 2400psi . I noticed the voltage on the icp was not stable , that and along with oil in the icp connector means the icp needs replaced . I did notice a hiccup where the icp dropped to 2000 psi momentarily, but I wonder if it's just the icp failing rather then an actual loss of pressure


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I don't think I've ever seen IPR% go above the low-mid 40s even pushing up a hill at full throttle. Mostly stock truck, not towing. As said, the PCM pushes the IPR duty cycle only up to what it needs to produce sufficient injection pressure (ICP) to do the job. Still, if you've got oil in the connector and unstable ICP readings, it's wise to replace it.
 

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Discussion Starter #5
Yeah for whatever reason I thought that duty cycle spiked real high then as the rpms built it would slowly move down . I'm trying to get all avenues sorted before I pull the trigger on a set of injectors. $$$$


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IPR % is how far the IPR valve is open, the higher the number, the more open the valve is.

If it was at 80%, then it would be dumping almost all of the oil pressure back into the reservoir, and the HPOP wouldn't build ANY pressure.
So under higher RPMS, where there is more demand, the IPR % should be lower right?

Or do I have that wrong?
 

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You have it backwards. Ipr % is how much it's closed.
 

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Discussion Starter #8
Thanks for the clarification. It would seem that with 270k on the truck the injection system is in good shape . The injectors all pass a buzz test and a power balance test . I suppose the oil is bypassing the poppets at higher load / rpm . Swamps will be getting some of my money tax time next year .


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That percentage is not a percentage of how FAR the valve is open/closed, but how much of the TIME. So within, say, 1 millisecond, a 30% IPR means the IPR is closed for 300 microseconds and open for 700 microseconds. That's why it's called IPR duty cycle %. And if I recall, the more it's closed, the higher the pressure builds (because it's basically a relief/release valve).
 
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