OK, I have been researching and researching this, but still can't get a straight and simple...should I shim the FP valve? I'm not getting any codes or having any issues, but I haven't really started messing with LiLY yet.....I've read some guys sayin its a great mod and some who say they started getting codes AFTER they shimmed...so with. Any ideas fellas?
FPRV....to shim or not to shim
- Thread starter mattv
- Start date
Ive always had good luck shimming the fprv. If you do it wrong and don't get it straight you stand the chance of ruining the fuel rail/fprv. Most people will do a race valve as its a remove old install new and your done. If your not getting any codes or reduced performance then you are probably fine., least for now. Some fprv's seem to be weaker/fail sooner than others. What do you plan on doing with the truck?
Search "Bottle test" ~ http://www.duramaxdiesels.com/forum/showthread.php?t=1995&highlight=Bottle+test ~
This will tell you if you need to shim your FPRV.
Search "Race Valve", This will tell you to not install a Rave Valve unless it's a race truck.
If some guys get low rail pressure codes from installing a shim kit, they more than likely installed it wrong.
Your straight answer........ If in doubt, shim it out.
Yeah I've read about the bottle test, and I could see how a guy could screw up installing those shims. Not gonna do a race valve as its a daily driver. I plan on building the truck up to about 450 rwhp...so nothing to extreme. I just see a lot of guys shim as one of the "standard" LiLY fixes.
If you run any kind of power, the LLY almost requires a shim because with a big pulse width, the rail pressure will spike on a shift and blow open the valve. It isn't usually a problem on smaller tunes though. I haven't seen it to be a problem with the LBZ or LMM though. They obviously changed that part when they raised the rail pressure in 2006. Maybe you should get a valve from an LBZ or LMM and just install that instead of shimming your stock one if you're worried about screwing up the shim job.
It's a pretty simple job, yet it can easily be screwed up....
Some tuners will straight up recommend it when running a built trans tune, some guys say to wait till it pops for the first time....
I waited for it to pop, happened while I was passing a car...
Personally, if you are going to be running a "big" tune, or something like a race tune from a built trans efi live file, it's probably a good precautionary measure, if you're going to be running stock trans efi live tuning it shouldn't be necessary.
You should bottle test the fuel rail if you're having issues, but it's not going to tell you anything in regards as to whether or not you should shim the rail, the bottle test will just show you if the FRPRV is functioning properly, the shim just increases the resistance of the spring that regulates pop off pressure and if installed properly the shim kit modification won't throw any codes, typically you'd get them before the mod
There's other less intrusive little "helps" for the LLY's fuel system, LBZ replacement parts for the FRPRV and pressure regulator for the CP3 are popular "upgrades" to echo what JoshH said...
Some tuners will straight up recommend it when running a built trans tune, some guys say to wait till it pops for the first time....
I waited for it to pop, happened while I was passing a car...
Personally, if you are going to be running a "big" tune, or something like a race tune from a built trans efi live file, it's probably a good precautionary measure, if you're going to be running stock trans efi live tuning it shouldn't be necessary.
You should bottle test the fuel rail if you're having issues, but it's not going to tell you anything in regards as to whether or not you should shim the rail, the bottle test will just show you if the FRPRV is functioning properly, the shim just increases the resistance of the spring that regulates pop off pressure and if installed properly the shim kit modification won't throw any codes, typically you'd get them before the mod
There's other less intrusive little "helps" for the LLY's fuel system, LBZ replacement parts for the FRPRV and pressure regulator for the CP3 are popular "upgrades" to echo what JoshH said...
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Shim kit is on the bench waiting to be installed on my LBZ. May not need it but I've been known to throw a low rail code occasionally and I already rebuilt the F2F head. Can't hurt.
Sent from my SCH-I535
Sent from my SCH-I535
I shimmed mine before it popped. Used 2 shims. If it had an aftermarket cp3 I might have used 3.
I've never heard much problems out of the race valve. I got a low rail about 2 years ago with my ppe. Installed the race valve at that time and daily drive my truck. Never had an issue after that. There's a tone of threads arguing back and forth. Mines been fine and it a hell of a lot easier to just pop the old one out and put the new one in. It is a pain to take out though
When I put my dual fuelers back on, I couldn't get the dqmn fprv out of the rail. I tried every tool combo I had with no luck. I have removed and installed it myself a hand full of times between installing a shim kit, race valves, and dual pumps before with no problems. I ended up having to take the entire rail out of the truck and using a vise.
That's why I haven't done it yet. I started to and about an hour into the job back and forth to the tool box to find the RIGHT tool and I decided a day when I had more patience would be a better choice.
Sent from my SCH-I535
Put the boxed end of a wrench on the FPRV, have a buddy hold it on there, jump to the passenger side of the engine and push with the heel of your foot. Lots easier than pulling by hand.
Don't think it is possible on an LMM. Firewall and cowling stick out and hangover a lot more then the previous years
If the valve is leaking past then I would go with a race valve since your spring in your valve is already weakened and you will just be wasting your time shimming it. Been there done that. If the valve is in good shape then your will probably have good luck shimming it. I would never buy a new valve, have you checked the price of them?
