LB7 FPRV Shim Mod ???

[MACKIN]

I think there is some confusing info here or maybe I'm confused.

I believe it's a FRPCV which is a Fuel Rail Pressure Control Valve which is what this topic is about that pops on a LB7 that is located on the driverside fuel rail. There is no shimming that I'm aware of except they are plugged.

I had mine pop and they don't throw a code but they sure make a mess.

The FPCV is located on the CP3.

I believe the whole shimming thing came about on the LLY motors of FRPCV . No?

 

[Mike_S]

For simplicity's sake, I generally refer to the solenoid as the FCA, or fuel control actuator (I believe this is how Bosch refers to it as well) and the mechanical relief valve as the FRPRV or fuel rail pressure relief valve. But thats just how I keep it straight in my head...LOL! That being said, what are you guys opinions on plugging VS shimming for a weekend warrior/partial daily driver? I'm leaning more towards shimming just for safety's sake, but...to plug it and take away a possible weak point in the fueling system is very attractive...

 

[05smoker]

For simplicity's sake, I generally refer to the solenoid as the FCA, or fuel control actuator (I believe this is how Bosch refers to it as well) and the mechanical relief valve as the FRPRV or fuel rail pressure relief valve. But thats just how I keep it straight in my head...LOL! That being said, what are you guys opinions on plugging VS shimming for a weekend warrior/partial daily driver? I'm leaning more towards shimming just for safety's sake, but...to plug it and take away a possible weak point in the fueling system is very attractive...

I for one am not a fan of plugging on an LB7. Injector bodies are too fragile IMO.

 

[Mike_S]

I for one am not a fan of plugging on an LB7. Injector bodies are too fragile IMO.

ooo, that is a very good point...Thats just what we need is a cracked injector body.

 

[MACKIN]

Mine isn't plugged but I recall the early LB7's had issue with them popping. From what I remember you could just get in there and tighten it back up I believe. I believe GM came out with a updated one as mine was replaced under warranty years ago. I do know that if you ran a early Pressure Box they were almost guaranteed to pop.

Nonetheless I believe there is nothing to gain there anyway on a LB7. It was the Lilly's where all this came about if I recall. On a heavily modified truck LB7 perhaps something has to be done,say a plug. Only the big dogs can answer that.

 

[DIESELMAFIAPER.LB7]

bottle test is much easier than trying to shim it to see if thats your problem ya know

Did that :thumb: a balance test an replaced every seal an bolt in the return side probably just need a bigger cp3 :rofl:

 

[Mike]

The lb7 and lly's needed because they would pop when rail pressure of much over 24,000 was created. The lbz and lmm already had facory pressure of 26,000+ so the earlier two needed help with shims.

 

[DIESELMAFIAPER.LB7]

Think ill plug it anyone got the size or should I just use some lbz shims as I have those available at anytime

 

[SDP]

I just tig'd the end of the banjo bolt shut, no issues so far.

 

[Vrabel]

I was told by a reputable source not to shim the LB7's. That it has an opposite effect to the LLY's and LBZ's. Thats why kit is not available.

 

[MACKIN]

I don't believe it's necessary unless you ramp up fuel pressure as Mike stated. Theres nothing to gain. If you have a early 01 although you'll have to address it as they have been known to pop even with out ramping up the fuel pressure. Been there done that


Rereading the original poster sounds like he has to address it

 

[S Phinney]

So far I've ran up to 27k and haven't popped mine yet. If you decide to modify it you would tap the end and install a plug then reinstall it. The return fuel can still go into the return line then. CP3's return fuel so it is necessary for it to work properly.

 

[Mike]

I was told by a reputable source not to shim the LB7's. That it has an opposite effect to the LLY's and LBZ's. Thats why kit is not available.

What's the opposite effect?

 

[ZeroGravity58]

What are you plugging? Are you putting a plug in the banjo bolt are in the fprv? I've been thinking about this for awhile since I started having problems holding rail pressure even when I had dual cp3s. My injectors passed the bottle test so I'm leaning toward the fprv not holding.

 

[Vrabel]

What's the opposite effect?

Maybe I understood wrong, but when you shim it it raises pop off press. The way I understood explanation was shimming a LB7 lowers pop off press. and was told to remove the washers
that were installed installed.

 

[joeracer01]

Adding shims (washers) will compress the spring mechanically and make it harder for the fuel to compress the spring from the needle side.
This means more fuel pressure will be needed to make it release / open.

 

[Vrabel]

I know that. That's why I couldn't understand why I was told it wouldn't' work on LB7

 

[ZeroGravity58]

It should work if you shim the spring on it. ive decieded im going to plug it i ust have to find out the plug size. if no one knows i will have to find one myself this weekend.

 

[S Phinney]

I think its a 1/2" allen head pipe thread plug. I got some from tractor supply and was going to plug it but never did.

 

[Vasbinder]

How do you know if it pops?