Defueling lly please help

[Salemn2010]

I have a 2005 lly that has a defuel problem. During hard acceleration(pedal to the floor) I will drop fuel pressure it only does it when full throttle any other time it is just fine. The trans dosent limp. And no trouble codes are set. During full throttle my rail pressure is around 25-26kpsi and it defuels to just under 10k. If I slow down to near 45 mph an let completely off the throttle it will go back to normal.

If anyone can please help me with this if you have any ideas of what it could be. I wanna get it to a shop. Just seeing if I can figure it out with some help of others first.

Efi live, raptor 150 gph lift pump, pcv reroute, cold side intercooler piping, egr delete, turbo resonator delete, lbz mouth piece, 4" down pipe 5" exhaust no mufflers or cats, 8" tip, edge cts insight

 

[Hoosier]

I'd try a PPE Race valve first. Am I wrong?

 

[Salemn2010]

I'm pretty new to the diesel word. What is a race valve? Does it just allow more fuel?

 

[03spoolindmax]

I wouldn't get a race valve. Just get a shim kit. The FPRV (fuel pressure relief valve) spring gets weak and bleeds off rail pressure. Search bottle test and it'll explain more. The race valve is just a plug that deletes the valve but isn't fail safe. The shim kit Retains the FPRV but puts more pressure on the spring to stop it from opening prematurely. It'll still bleed off if to much rail pressure occurs. The race valve being a plug will never bleed off pressure. You can get a shim kit for around $10 and the race valve is around $35. Do some research on here. There's lot of info on this site that'll help you decide.

 

[Salemn2010]

Thanks for the help. I'll look into it and see what I come up with.

 

[S Phinney]

Does it set any codes? Does it go into fail safe limp where it will only turn 2000 rpms?

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[WI Huck]

I wouldn't get a race valve. Just get a shim kit. The FPRV (fuel pressure relief valve) spring gets weak and bleeds off rail pressure. Search bottle test and it'll explain more. The race valve is just a plug that deletes the valve but isn't fail safe. The shim kit Retains the FPRV but puts more pressure on the spring to stop it from opening prematurely. It'll still bleed off if to much rail pressure occurs. The race valve being a plug will never bleed off pressure. You can get a shim kit for around $10 and the race valve is around $35. Do some research on here. There's lot of info on this site that'll help you decide.

The shim kit turns the factory valve into a race valve. The spring is so stiff already, by adding the shim it does not move.

We have replacement LBZ valves (higher PSI than the LLY) and the race valve here http://www.hdiesel.com/C/CommonRailComponents/288 .

 

[quinton]

You can use the race valve. Nothing wrong with it. Millions use it and no problems. I've actually NEVER heard of anyone having a problems with it. I run it.

 

[Salemn2010]

No limp mode no codes and the truck will go to normal rpm range just a loss of rail pressure and power letting off the accelerate won't allow it to build pressure back up you have to slow down enough for the truck to idle down all the way then the rail pressure will build again. It's almost like it's something electronic not mechanical but it dosent set any codes

 

[WI Huck]

How many miles on it?

 

[TLyons90]

X2 on a shim kit. Race valve works as well but why take a chance with problems if the shim kit will do the exact same thing for cheaper?!

 

[quinton]

Why do you guys keep saying the race valve will cause problems? Do you personally know anyone that has had a problem with one or is this just what y'all have heard?

 

[TLyons90]

Why do you guys keep saying the race valve will cause problems? Do you personally know anyone that has had a problem with one or is this just what y'all have heard?

Its a chance! Why take a chance? Yes hearsay is that people have had issues but have never heard any issues from a shim kit that does the exact same thing.

 

[quinton]

Its a chance! Why take a chance? Yes hearsay is that people have had issues but have never heard any issues from a shim kit that does the exact same thing.

You say why take a chance? Your taking a chance with a tuned truck... But like I said. NOBODY you know personally or have a name to give has had a issue. Everyone goes off of "what they have heard" rather then what they have tested. Shim kit can still pop open. I had one on a customers truck and it didn't work. Still popped open put a plug in it boom fixed it. Still running fine after 3 years just like my truck and every other truck I've put one in. Not trying to start anything or be rude.

 

[TLyons90]

You say why take a chance? Your taking a chance with a tuned truck... But like I said. NOBODY you know personally or have a name to give has had a issue. Everyone goes off of "what they have heard" rather then what they have tested. Shim kit can still pop open. I had one on a customers truck and it didn't work. Still popped open put a plug in it boom fixed it. Still running fine after 3 years just like my truck and every other truck I've put one in. Not trying to start anything or be rude.

All good! Moral of the story either works depending on which way you prefer to go!

 

[WI Huck]

There are more potential problems with the shim kit. The shim kit is a few dollars less than a race valve, but you have a lot more time involved. If you want the protection buy the LBZ valve and sleep tight.

 

[quinton]

There are more potential problems with the shim kit. The shim kit is a few dollars less than a race valve, but you have a lot more time involved. If you want the protection buy the LBZ valve and sleep tight.

??? A stock Lbz relief valve???

 

[LWATSON]

I wouldn't do anything until I did the bottle test. Although the LLY relief valves are easier to pop off than LBZ and newer, allot of them have been shimmed or replaced with a race valve that didn't need to be.

 

[Andrew]

At the risk of sounding like an idiot, wouldnt the fprv popping off cause a low rail code since all the truck knows is its commanding x amount but only has y amount?

 

[PACougar]

This all sounds too dangerous to me, burn the truck to the ground to be safe and buy a new one.