LBZ P0087 Low Rail Pressure

[AZBio]

Please Help! Truck loses power and throws the Low Rail Pressure Code around 2000 rpm's. Truck runs great under 2000 rpm's. I gain fuel pressure all the way up to 12k psi, but as the rpm's get higher and the commanded pressure increases the fuel pressure drops drammatically to 7k when commanded is asking for 30k+ psi. Any ideas?

Thanks!

 

[AZBio]

Forgot to mention, the check engine light usually turns on in third gear. It isn't 2k rpm limp either as I can still get the rpm's over 2k, the truck just doesn't seam to react.

 

[DmaxHawk]

When was the last time you changed your filters?

 

[x MadMAX DIESEL]

shimmed the fprv?

 

[JoshH]

Your truck should never command 30k+ PSI. The stock sensor is only good to just over 29k PSI. Stock rail pressure is a max of right at 26k PSI.

You should try to get a gauge on it to make sure the Air Dog is putting out pressure. If it isn't running, it can cause a restriction, but it shouldn't be enough to cause that serious of a rail pressure drop unless you are really getting on it. How many miles are on the truck?

 

[AZBio]

When was the last time you changed your filters?

I have changed them already thinking that was the issue, but it didnt fix it. It is not the filter housing either.

 

[AZBio]

shimmed the fprv?

No, But I was thinking about ordering the PPE race valve.

 

[AZBio]

Your truck should never command 30k+ PSI. The stock sensor is only good to just over 29k PSI. Stock rail pressure is a max of right at 26k PSI.

You should try to get a gauge on it to make sure the Air Dog is putting out pressure. If it isn't running, it can cause a restriction, but it shouldn't be enough to cause that serious of a rail pressure drop unless you are really getting on it. How many miles are on the truck?

This is my brothers truck, but it has all the same equipment on it as my signature. It has 114K miles on it. We have checked the airdog and it is definatly moving fuel.

 

[lotsofmiles]

grab ahold of your fuel lines into and out of the filter.

then do the same on the flexible lines from the tank to the filter.

my lines were soft and cracked, into and out of the filter, allowing them to pinch closed

edit, oh now i see air dog...

 

[x MadMAX DIESEL]

Still sounds like its starving for fuel, you should really put a gauge on the airdog... Did you actually test that it was moving fuel, or just hear it running? I've had pumps die before but the motor still worked.

 

[AZBio]

Still sounds like its starving for fuel, you should really put a gauge on the airdog... Did you actually test that it was moving fuel, or just hear it running? I've had pumps die before but the motor still worked.

We had the same thing hapen last year. Pump on the airdog was running but not moving fuel. If I hit the schrader valve next to the alternator while the airdog is running, it sprays fuel over the core support.

 

[dirttymaxx]

grab ahold of your fuel lines into and out of the filter.

my lines were soft and cracked, into and out of the filter, allowing them to pinch closed

x2
found this a few trucks

also if you,used rubber line to plume in the air dog check them as well.

 

[AZBio]

Does an injection pump slowly wear out? Or is it one of those "it either works or it doesn't"? I have checked for leaks in the fuel lines, to which I couldn't find any. I am leaning more toward the FPRV or Injection Pump. The truck also has a slight knock and has trouble starting when hot. Starts great in the mornings, but after driving it it sometimes takes cranking it for a minute or two to start.

 

[DIESELJEFF]

did you ever get the truck fixed?? im having identical issues .

 

[blackdirtymax]

Cp3 pumps can get weak and not maintain rail pressure


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