Loss of fuel pressure

[DarrenKling]

2012 6.7 loss of fuel pressure after truck warms up. Sent injectors in had tested on 2 different benches one being a bosch bench passed,reinstalled with new injector feed tube all torqued to spec. Replaced cp3 (high pressure pump) with FCA,fuel filter and lift pump test done by volume and pressure readings. Im still losing fuel pressure any help would be great!

 

[AH64ID]

What are the indications of a loss of fuel pressure?

 

[DarrenKling]

What are the indications of lose fuel pressure?

Loss of power and watching pressure drop on my snap on verus scanner

 

[AH64ID]

Have you verified the pressure sender is operational?

 

[DarrenKling]

yes also fuel rail and sensor and pressure relief replaced

 

[AH64ID]

Is it throwing a code with the loss of pressure/power?

Can your scanner show rail pressure actual vs rail pressure demanded?

 

[DarrenKling]

Yes p0087 fuel rail pressure low

 

[DarrenKling]

Yes it shows demand and actual and it cant match demand pressure

 

[EDankievitch]

Bad blow off valve on fuel rail?

 

[DarrenKling]

Earlier post with replaced fuel pressure relief valve (blow off valve) has been changed already

 

[sag2]

Wow, since you have replaced virtually everything that is related I would try the following diagnosis instead of replacing parts. Get three injector cap off tools and a fitting to tee into the high pressure fuel pump feed line between the filter and high pressure pump.
Start by watching the fuel pressure feeding the CP3 pump while the rail pressure begins to drop on the scan tool. Just trying to verify the lift pump isn't failing when everything is hot. Since you already know the PRV is not leaking, but to be sure, get a Miller 9012 fitting to put in place of the banjo so you can actually measure the flow (or lack of) when the rail pressure drops. If that tests good, cap off two or three injectors at a time to confirm a leak on the high pressure side. If your capping three at a time it is best to cap every other cylinder in the firing order.
By that time you have to have it narrowed down.

 

[DarrenKling]

Sorry i forgot i put my lift pump pressure gauge on average 12-13 psi at idle and not ever below 6 while driving, lift pump pressure hasnt dropped when rail pressure starts to drop,rail pressure stays good until coolant temp hits around 195-200 then pressure tanks

 

[sag2]

Ok, you need to focus on capping off injectors.
The other thing you could do is monitor the fuel return from the injectors as the temp comes up.