when does shimmed rail "pop open"

[x MadMAX DIESEL]

i put in 3 washers when i shimmmed my relief valve. at WOT the truck demands 25000 psi but im getting 20000 MAX then fades off to about 18000. i think my valve is popping open and releasing the rest of the fuel. when SHOULD one of these pop open? 24000, 26000, etc. etc.

 

[JoshH]

Do a bottle test.

 

[MMLMM]

Do you have a lift pump?

EDIT: I dont know how I missed that in your sig.

As said try a bottle test, see if it is in fact getting by the FPRV

 

[x MadMAX DIESEL]

Do you have a lift pump?

EDIT: I dont know how I missed that in your sig.

As said try a bottle test, see if it is in fact getting by the FPRV

dont have a clue how to do a bottle test... guess i can ask my teacher about it and maybe i can bring the truck to school and test it out.. but idk what else it could be, ive got my lift pump probably pushing more fuel than half the guys on the site and i still cant get over 28 PSI of boost, and the truck lays on its ass when running the 135 tune still.

 

[Kat]

http://www.duramaxdiesels.com/forum/showthread.php?t=1995&highlight=bottle+test

 

[stacks04]

10 pounds of lift pump pressure should be more than enough for you needs. second a rail valve open should show on a log. you'll max pressure and then it drops quickly and significantly. a bottle test will show you the best though. do a search for it and it is actually simple. with 3 washers in it it should not pop unless you have a knick or bur on the housing. again bottle test will show it though.

28 psi boost isnt bad for a stock turbo but you can easily attain 32. how are you measuring it? what are your egt's like?

 

[JoshH]

dont have a clue how to do a bottle test... guess i can ask my teacher about it and maybe i can bring the truck to school and test it out.. but idk what else it could be, ive got my lift pump probably pushing more fuel than half the guys on the site and i still cant get over 28 PSI of boost, and the truck lays on its ass when running the 135 tune still.

Unless the valve was damaged when it was shimmed, I doubt it's getting past it.

 

[x MadMAX DIESEL]

second a rail valve open should show on a log.
28 psi boost isnt bad for a stock turbo but you can easily attain 32. how are you measuring it? what are your egt's like?

i dont have live so idk if i can "log" a run. im just going off my quad live data scanning.... i measure boost with a mechanical autometer gauge tapped on the aluminum intake between the grid heater and the intercooler boot.
no idea on the egts either as i only have the one boost gauge as of now. i will be getting a pyrometer and fuel pressure gauge in the near future...

since i dont have a fuel pressure gauge now i have my lift pump turned up enough that there is almost 1/2 inch of threads visible on the adjstment screw (bad idea maybe)... i only have this up that much because i was stumped that i could only get 28 psi boost and tryed pushing more fuel to help it out

 

[Big Block 88]

Do you guys have a Tech II at your school? I would hok it up and check your readings.

 

[x MadMAX DIESEL]

not sure, im guessing we do. what do you suggest i check on the tech II though?

 

[Big Block 88]

How do you know your comanded and actual psi? Does the quad do that? I was missed that your post somehow.

I'll just say X5 for the bottle test then.

 

[x MadMAX DIESEL]

How do you know your comanded and actual psi? Does the quad do that? I was missed that your post somehow.

I'll just say X5 for the bottle test then.

yes, the quad can do that... and im about to bottle test now. well see in just a second

 

[x MadMAX DIESEL]

having big trouble getting the dang U connection hose off the rail

 

[Burn Down]

Long curved needle nose pliers, pull the hose and the clip off together. The hump on the fittings is a PITA to get the clamps to slip over. It worked good for me.

 

[x MadMAX DIESEL]

i got the clamp off but no luck getting the actual hose off. ill try again tomorrow

 

[JoshH]

Try putting a pair of needle nose pliers on the hose behind the nipple and twisting it to break it loose from being stuck on there. Should help it come off a little easier.

 

[WICKED DIESELS]

Once the rail relief valve blows open a couple of times, the spring gets weak as the fuel passing through such a small restiction becomes super heated. When this happens it keeps blowing open, until the spring becomes so weak the truck won't start. The seat can also erode from the high pressure, just as a water jet cuts metal.

 

[stacks04]

as far as scanner readings go you want to log main rate mm3, actual fuel rail vs desired rail pressure. this will tell you exactly. not sure on the quads tuning but it takes a decent shot of fuel to run down the rail pressure with a lift pump. i would stop by a dealer or maybe even your school has one, but get the vacuum/pressure gauge that taps into the port on the engine. then you can see what your lift pump pressure is to set it right. 7-8 lbs is plenty.

 

[x MadMAX DIESEL]

just took a spin, felt okay actually. tryed to watch the road and quad at the same time...pretty dang hard actually at full throttle lol. anyways fuel rate was about 47-48 and act psi was 22000 and commaned was 26. just got new battteries today maybe my pump wasnt getting all the power it should have been gettting?

 

[stacks04]

full throttle the main rate should be 99-100 not 47-48. but i digress, wait for one of the lbz guys to chime in on the pressures. 21k is about the min on the lly,lb7 where max is 23k. going on the same logic the 22k seems a little low. if it is maintaining it though then it is not the relief popping.