Rail pressure same as low pressure fuel

Aussieatlarge

New Member
Nov 11, 2021
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My rail pressure has been all over the place lately. Dropping under load and causing limp mode.
Tonight the railPressure dropped to be equal to the low pressure. It moves exactly with the low pressure, around 80psi. But the car still runs. How is this possible? If it requires 1500psi, how does it possibly run at 80 (albeit in limp mode). I assume the hpfp is toast, right? Can Indrive to work tomorrow?
 

Aussieatlarge

New Member
Nov 11, 2021
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Was just reading that the fuel control valve opens all the way in limp mode which explains the same fuel pressure in feed line and rail. It also probably confirms that the pump is dead because it is adding no pressure. Geez. That’s a mds80 6 coils and a hpfp in a few months. Just injectors and she will be like new, ok maybe vanis and lpfp
 

Aussieatlarge

New Member
Nov 11, 2021
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This was my low pressure and high pressure fuel pressure reading prior to the ecu going into full time limp mode. Are the low pressure oscillations causing the high pressure pump rail pressure to drop to 124psi or is the high pressure pump causing the low pressure signal to bounce around? Note that the low pressure is really smooth until the high pressure starts dropping. Chicken and egg
 

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