LBZ: 200k mile LBZ low rail pressure

[diesel53]

Guys,

We have an LBZ with a fass 150 and under a load throws a low fuel rail pressure code.

Rail pressure w/edge juice on level 4:
-desired 26K
-Actual 19k

Rail pressure w/out edge stock tuned:
-desired 25K
-actual 18K

All injectors were within +-3, most around 2. Fuel rail fitting is modified to Ppe specs.

I don't think with only 200k miles the cp3 is weak but who knows. Anyone have any advice before we start throwing money at it?

Note: it only throws the code when the edge is installed but either way actual pressure is low.

 

[IOWA LLY]

The injectors are probably returning excessive amounts of fuel.

 

[Chevy1925]

Max race tune or stock tune?

 

[clrussell]

The injectors are probably returning excessive amounts of fuel.

This

 

[Awenta]

This

X3. Easy enough to check. If they in spec then check the cp3.


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[bbolden516]

Do you have a race plug or shimmed stock returned they can be difficult and not properly reseal completely once popped.

 

[diesel53]

Fuel rail fitting has been enlarged to Ppe specs.

When the edge was tested it was on level 4 which is the race tune I believe.

Injector return test "beaker test" was within spec but the accuracy is questionable.

 

[Awenta]

Test cp3 return


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[KyleC4]

What about ramping up rail pressure at idle? Command fuel pressure regulator all the way up at idle and what is actual vs desired. Only suggesting this cause I've had vehicles that could make commanded pressure at idle but not under load. Also have you put a vacuum/pressure gauge on test port and see what readings are while driving?

 

[Awenta]

I assume the pump is running and you've changed filters right?


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[diesel53]

Yes filters are new, pump is running.

What would testing the cp3 return troubleshoot exactly?

 

[Chevy1925]

Yes filters are new, pump is running.

What would testing the cp3 return troubleshoot exactly?

how worn it is.

if the injector return test is questionable, you need to rerun it so we know for sure. if they do come back good, CP3 time

 

[mebob2001]

Test the fuel.pressure releaf valve. If that's fine. Remove. Return lines carefully and should see less then 4ml of fuel in 15 seconds of idling. U can also just test each back all in one. To see if that is the issue. One return line goes right being the glow. Plug control module. Be very genital and do not bend of break the nipple off. U can remove without removing the module. Just unplug it. The passengers side if under the intake horn just in front of the egr valve.

I have seen trucks start and run even meet rail pressure bang on and return more then 16 ml of fuel per bank. They were 20ml plus. Anyways good luck


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[Brent@LDS]

I bet you find its injectors returning to much fuel. We see this problem weekly here!

 

[WVRigrat05]

Mine did the exact same thing when the returns were almost wide open.

I had a lift pump at 15 psi, race plug, and new lines turned out to be injectors.