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steeler

After treatment fuel pressure problem

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Hey guys I've got a 2015 lei that is throwing a p20de00 after treatment fuel pressure sensor circuit range/performance fault.

I've run through the diagnostics with tech tool with exception of the final test because I don't have the special tool to do it, but everything checks good. 

The afp runs about the same as engine pressure when the shutoff valve activates, then runs about 45 lbs deactivated. Engine fuel pressure is steady at about 58-60.

Any ideas?

 

Forgot to add that I replaced the doser module. 

Edited by steeler

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Aftertreatment fuel psi should be what.... 90ish psi? What test is it that you can not perform that requires a special tool?

 

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13 hours ago, turckster said:

Aftertreatment fuel psi should be what.... 90ish psi? What test is it that you can not perform that requires a special tool?

 

I was wrong on that test, all it was was checking the fuel pressure to the shutoff valve, which is the same as the engine pressure. That was the last test, so it just told me "no fault found". 

I hooked up another truck of the same year just to compare pressures. That one had an after treatment fuel pressure of 90 psi when the shutoff valve opens, then dropped to zero with the valve closed. Mine stays at about 45 with the valve closed. I'm going to run regulated shop air to the shutoff valve at 32 psi just to see if anything changes.

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Ok hooked shop air to the shutoff valve, that didn't change anything. So if my test vehicle has after treatment fuel pressure of 90, with engine fuel pressure at 60, what "ups" that pressure? I thought after treatment fuel pressure would be equal to engine fuel pressure?

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There is a fuel pump mounted behind the module, small little electric pump. When activated it boosts engine fuel psi to 90ish to help atomize fuel at the nozzel. 2007 emission non-catylized engines have the same pump but they are mounted inside the right frame rail mid-chassis. 

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Mine does not have the separate pump for after treatment, but I found the problem. The 7th injector was plugged up. Mack needs to fix some issues with the guided diagnostics in tech tool, it never mentioned anything about that as a possibility for the code I had. Oh well all good now. Thanks.

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