I have a question for all of the fuel experts. I have been reading in all the forums and iam sure that it is in here somewhere but have not found it yet. I hear everyone talking about replaceing, shimming, etc. the fuel pressure regulator. I have the books on the truck but the only regulator I have found is the one on the cp3 pump. The guys here talk about it being on the driver side firewall side, and talk like its not a big job to do, so there must be another regulator or its called something else in the books. Does anyone have any pictures of this regulator and the shim mod, I do have the dreaded problem of the lost power and have not had a chance to do any troubleshooting other than some forum searching. Also where you plug into to test for the fuel pressure/vaccum. Thanks for any information.
mydmax05
It's actually the FPRV(fuel pressure relief valve) on the back of the fuel rail. If your mechanically inclined it's not a real difficult job but I wouldn't call it easy. You need a 6pt wrench, I forget what mm, think it's a 18. I pulled mine and shimmed it but it only worked a year or so. I ended up getting lift pumps and replaced my FPRV with a new one(not shimmed) and had no more issues.
Correct, or you can save the trouble and install a race valve. Much easier! 
http://www.hdiesel.com/C/CommonRailComponents/288
http://www.hdiesel.com/C/CommonRailComponents/288
I shimmed mine a couple months ago. Other than being in there tighter than *%&()# its not a hard job. Getting access and having the wrench fit correctly is the key, I ground flat a boxed end wrench (took off taper on wrench) to ensure full engagement on the valve.
I haven't messed with this since I sold my LLY. I haven't ran any tunes in my LMM's. But shimming the FPRV makes it harder to open but it "will open" if needed.A race valve will not open under any circumstance, correct? Which may not be necessary ???
It is way more expensive, but in my experience(several years ago) it was better to bite the bullet and add a lift pump/s. Shims/race valves are a band-aid. Like eveything else with these trucks, you got to pay to play...... when it gets down to it ! Better on your system to go ahead and do it to begin with IMHO(seeing as how I ran a much bigger tune and never had an issue with a stock FPRV while running lift pumps).
It is way more expensive, but in my experience(several years ago) it was better to bite the bullet and add a lift pump/s. Shims/race valves are a band-aid. Like eveything else with these trucks, you got to pay to play...... when it gets down to it ! Better on your system to go ahead and do it to begin with IMHO(seeing as how I ran a much bigger tune and never had an issue with a stock FPRV while running lift pumps).
Is there a way if you had the fprv removed, can it be bench checked for condition. Thanks also for the informatio from all of you.
Another question about fuel, can you replace the fprv with a newer modle and what would the diffence be, and can fuel injectors be replaced with newer modles, would it make the truck quieter also. Ya I know I need to fix one thing at a time.
Another question about fuel, can you replace the fprv with a newer modle and what would the diffence be, and can fuel injectors be replaced with newer modles, would it make the truck quieter also. Ya I know I need to fix one thing at a time.
The FPRV is meant to open. The shim kit I bought had 3 washers I believe. One was supposed to be sufficient but two recommended, I did two. I could not have told you the difference from stock. Don't know about injectors. But when I started having trouble with my FPRV after it was shimmed, I bought a race valve and it still 1093'd on me. Now I don't know if it was tight enough, but I know it was not leaking. I still ended up doing lift pumps and got a new FPRV. JK of Kennedy diesel told me early on that I would need to do this but I tried skirting around it and a year or so later, I did it the right way.
When you are shimming the spring you are increasing the pressure needed to open. How much depends on the thickness of the shim. From what I have seen, the shims are thick enough to bind up the spring and therefore rendering it a plug. If the shim is too thin it could come apart with the high pressures that are there and erode causing debris which the injectors will not approve of. Injector spring shims are expensive. If you want to have a working valve use the one for the LBZ, which is the one we sell. The opening pressure is higher and it has fewer failures than the LLY.
Thanks for the info. ! I knew it wasn't necessarily supposed to open but it is made to be able to as an emergency measure. I never did a bottle test on my LLY.
Like I said, I haven't messed with this stuff since I sold my LLY. The FPRV problems and rebuilding an Allison(unplanned), was enough for me to quit throwing tuners on my trucks.
Like I said, I haven't messed with this stuff since I sold my LLY. The FPRV problems and rebuilding an Allison(unplanned), was enough for me to quit throwing tuners on my trucks.
Thanks for all the input, I will be changing the fuel filter first this weekend , if that does not do the trick then I will do the bottle trick. Note: this did seem to come on about the same time that I changed my fuel filter head assy. (cracked/with wicks filter) so not sure if its just a coinsidence or not.
Well guys I thought I was going to get on here and tell you that I had it fixed, but after changing the fuel filter and after about 50 miles it did it again, and it was not under hard acceleration. I reset code and got on it a few times with no issues, I also noted that my fuel light was on and refueled, it was after I refueled that I got on it with no faults. Is it possible that the tank could have some crud in it. I ran it to work this morning with no issues, also why did this do this again after 50 miles when befoer I changed my filter it did it all the time. Guess I still need to do the bottle test dont I ?
I finally got around to doing the bottle test tonight and the results are in, it dumped about 1/4 of a 2 litre bottle. That sucks, guess I need a fuel pressure regulator? Dont quite get it though wished I had a scematic of the fuel system, when I removed the fuel line from the rail the end to plug, fuel came out , so doesnt this mean that fuel would be present anyway, is the line that I plugged going back to the fuel tank, and the one that I hosed under pressure. Still dont see the fuel pressure regulator though, any pictures anyone has or another thread with pics would help, thanks again.
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