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c-mac

Loosing aftertreatment fuel pressure on regeneration

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I have a 2012 chu613 MP8 that as the duty cycle gets  to 10% or so, the A'treatment fuel pressure drops from 8 to 15 psi under engine fuel pressure which is running in the upper 60's. The exhaust temps never get higher than 750deg or so and wont complete the regeneration. This particular unit has a 7th injector with the "T" fitting on top where the air and fuel lines connect.  Just wondering if any of you have seen this and what you've done to correct it. I thinking it could be either the 7th injector, the shut off valve or the T fitting on top of the 7th injector. I've been working on a large fleet of these trucks from 08 t0 13 models for 8 years and haven't ran into this before.

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Dang! Thought someone would have seen this.

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Only time I've run into this problem was after the customer had replaced the fuel filter head and put the check valve fitting in the wrong port. 

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Never seen that particular situation. Is 10% the highest duty cycle the 7th injector gets or does it get higher? Is aftertreatment fuel psi low across the board?  I've had to replace the shut off valve because of low fuel psi. 

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On ‎1‎/‎27‎/‎2019 at 8:37 PM, steeler said:

Only time I've run into this problem was after the customer had replaced the fuel filter head and put the check valve fitting in the wrong port. 

I just cleaned the Tee on top of the seventh injector where the air and the fuel connect. Now its been on regen 45 mins and only reaching 768deg on outlet temp and the fuel pressures are both steady at around 68psi. and 12% duty cycle. Theses numbers have been the same for 10 mins. The adaptive factor is holding and 1000. I would think it should rise if the temps were not coming up.

Edited by c-mac

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On the old style water cooled 7th injectors. When flow testing them using Tech Tool, they should make a chirping noise. The dealers have a flow meter they hook to them and check actual flow. 

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Put a new 7th injector on and took care of the problem. thanks

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