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| 05-11-2018, 05:22 PM | #1 |
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Private
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Rep 74
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Low pressure fuel pump
I installed a jb4 tune for my 2012 550. When I push it disables cylinder 7&8. Code says fuel pressure below target. I checked my low fuel pump pressure with jb4 connect and it reads around 9psi. Sometimes it will go down to 5-6 and sometimes it’ll be at 20ish. Is this normal? Thanks
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| 05-11-2018, 05:59 PM | #2 |
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Major
 
801
Rep 1,214
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LPFP output should be in the 50-70PSI range.
The HPFP will draw a vacuum on the tank in on itself of 5ish PSI. Something is wrong, likely the means of measurement. |
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Appreciate
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