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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29442
Experience:  GM Grand Master Technician 2007. 14 years experience.
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I need someone's help on a 2011 duramax 2500hd lml.. Fuel

Customer Question

I need someone's help on a 2011 duramax 2500hd lml.. Fuel pressure relief valve staying open and fuel go into the return line, which is making it lose fuel pressure and causing a extended start
Submitted: 1 year ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 1 year ago.

Hi there, I am Cam. Are you testing return flow from the fuel pressure regulator #2 in the front of the drivers side fuel rail or overall return flow?

Customer: replied 1 year ago.
The FPRV #2
Expert:  GM Tech (Cam) replied 1 year ago.

OK, do you have any codes set?

Customer: replied 1 year ago.
No codes set. I ran a test and The FPRV 2 is staying open
Expert:  GM Tech (Cam) replied 1 year ago.

OK, That is also a regulator. So with it running and at 1800 rpm, what is the amount of fuel returned through that line at WHILE at 1800 RPM for 15 seconds?

Expert:  GM Tech (Cam) replied 1 year ago.

I guess the long and short of this is that if no codes are set and that valve is returning too much then it needs to be replaced. Are you sure this is not covered by diesel warranty?

Customer: replied 1 year ago.
I been reading and studying duramax fuel system top to bottom over and over, so I decided to run a test on it.. I hooked everything up to my fass lift pump that I put on my truck, it only puts out like 14 psi and I checked everything and it was allowing fuel to leak out of the return nipple where the rubber hose is at.. I pulled the starter relay and jumped it across the relay to spin the motor over and it was really blowing a lot of fuel out then
Customer: replied 1 year ago.
I have already replaced the FPRV #2 and it still did the same thing
Customer: replied 1 year ago.
But now here is where it gets tricky. With the key turned on, no dtc, lift pump running and putting out 14 psi, if I unplug it or the FPS or the FRPR #1 it will set off a dtc and say reduced engine power but now I when I plug the FRPR #2 back in I can hear and feel it click and close.. And with the lift pump still running it quits leaking fuel.. But some as I either crank my truck or clear dtc it opens back up
Expert:  GM Tech (Cam) replied 1 year ago.

OK,m you are aware that by its design, there is ALWAYS some return flow from the injectors and that fusel flow is the result of the injection system using a bit of fuel to open the injectors?

And to be sure, you replaced the regulator in the end of the fuel rail? IF so, then did you remove the fuel regulator in the pump and inspect for debris there? I have a bulletin that may interest you.

Customer: replied 1 year ago.
I replaced the FPRV at the end of the rail and plugged the FPRV on top of the injector pump and there was no debris or metal shavings or anything. I understand that there is always fuel returning, but the FPRV on the fuel rail shouldn't stay open on the time. How can it build or hold pressure the the FPRV is open?
Expert:  GM Tech (Cam) replied 1 year ago.

Tell me how much fuel you measured over how long of cranking time?

Customer: replied 1 year ago.
I haven't measured it yet but it was a steady flow... Just the lift pump At 14psi you can see fuel coming out..
Customer: replied 1 year ago.
On the electrical plug that plug into the FRPR #2 there is 2 wires, are they both ground or hot or one hot and one ground? What kinda of voltage should they be reading?
Expert:  GM Tech (Cam) replied 1 year ago.

Without your lift pump though. These don't use a lift pump normally so you supplying fuel all the time, it has to go somewhere. The systems uses amperage on that to control it. With the engine running at idle, it should be reading .2-.7 amps dc. More than this indicates a leak. IT may require the whole fuel rail not just the valve replacement.

Customer: replied 1 year ago.
With my truck running if I plug my FPRV 2 the truck dies, same way with the FPS
Customer: replied 1 year ago.
I'm gonna try to do a video or some pictures for you
Customer: replied 1 year ago.
If I unplug my FPRV 1 what should happen?
Customer: replied 1 year ago.
Okay I did a test, at idle I'm getting about 85ml and at 1800 rpm I'm not getting anything.
Customer: replied 1 year ago.
Are you not interested in this anymore? Do I need to get another tech?
Customer: replied 1 year ago.
I would like a different expert, thanks