Interesting findings after Dyno Days - Pressure Relief Valve Failures

[Tomeygun]

well i guess we need to get the part number off of the 8. 3 CP3 in a QSC 540 HP. Maybe somebody can go over to one of those marine website/forumns and see if you of those guys will get us a CPL # or a CP3 # of their 540 HP engine and then see if it will bolt up

Will it ever end? hehehe, I hope not...



Would that be the stuff? A CP3 from a 540 8. 3L HPCR cummins on a little ol' 5. 9

 

[jwilliams3]

I wonder if those are rear gear train?

If they are they wont work.

 

[Tomeygun]

I wonder if those are rear gear train?

If they are they wont work.

http://www.cmdmarine.com



I thought I saw a pic on there that showed the CP3 on front and turbo on rear... Heck I think I will have to see it in person to figure it out

 

[Scrappy]

http://www.cmdmarine.com



I thought I saw a pic on there that showed the CP3 on front and turbo on rear... Heck I think I will have to see it in person to figure it out

If the pic is representative, I saw a fwd geartrain on the QSC8. 3 in the marine brochure.

 

[nickleinonen]

4930441 425HP QSB injector around $275 each

??? plus core or what?? that doesn't seem all that bad for the injector price. .

 

[Tomeygun]

??? plus core or what?? that doesn't seem all that bad for the injector price. .

does anyone know the part# for our injectors? (cummins, not dodge)

 

[JStieger]

does anyone know the part# for our injectors? (cummins, not dodge)

For my engine number (305/555), Quickserve shows #3949913



I have a subscription for up to 5 ESN, with 3 used already (my 03 HO, a 04. 5, and a 12 valve) so if you give me your ESN , I can look it up for a SO.

 

[Reb.B]

Okay, here some more to mess with your mind. Cummins has out (SUPPOSEDLY) and will have in '07 trucks a 375 HP 750 TQ 6. 7 litre engine and it is supposed to have a 4 piston pump, CP4. Okay, who's next?

 

[JVolpe]

TG



Did the trucks showing low rail pressure have noticable symptoms of power loss or engine performance issues?? I really want to know if I need a relief valve or not.

 

[Tomeygun]

TG



Did the trucks showing low rail pressure have noticable symptoms of power loss or engine performance issues?? I really want to know if I need a relief valve or not.

100% yes, IMO... 3 trucks, all 66mm turbos, all with TST/EZ stack.



yet mine was highest at 524, one at 470ish, and one at a terrible 417hp...



all in 1:1 ratio in trans, but the two low HP ones had dl'ers at one time, and both had tried the TS ramifiers too. The truck with 417 only showed a high of 11k on the rail PSI monitored with a DRB3.







As for on the street performance, both owners had not throught they were losing that kuch power, so its hard to say if you can feel it from S. O. P

 

[jwilliams3]

Tom,

What year trucks?

 

[Tomeygun]

Tom,

What year trucks?

All 03 models - But mine was the only 250hp S. O. motor, the others were H. O 305hp models

 

[TCluff]

All 03 models - But mine was the only 250hp S. O. motor, the others were H. O 305hp models

i was expieriencing low rail pressure at one time, and found out it was not the rail relief, we had found it to be a leaking injector that was dumping the rail pressure back into the return line on the rear of the cylinder head, rail pressure loss can also be had with a bad connector tube not torqued properly, or not seating just right into the inj...

 

[strokerschmoker]

I too think that I have fallen victim to the relief valve. After dyno'ing on Saturday I found that the more fuel I demanded the lower the HP went. For example, I ran the TST at 7/7 and the ramifier about 65% and it made 402 HP, then TST at 7/7 and ramifier at 100% made around 370, and lastly, TST 9/9 and 100% ramifier made less HP then the two previous runs. I could not tell at all by the SOP that the valve was bleeding pressure off, but it is kind of hard to not believe the proof of the dyno. How involved is the precedure to change this valve?

 

[SRadke]

I too think that I have fallen victim to the relief valve. After dyno'ing on Saturday I found that the more fuel I demanded the lower the HP went. For example, I ran the TST at 7/7 and the ramifier about 65% and it made 402 HP, then TST at 7/7 and ramifier at 100% made around 370, and lastly, TST 9/9 and 100% ramifier made less HP then the two previous runs. I could not tell at all by the SOP that the valve was bleeding pressure off, but it is kind of hard to not believe the proof of the dyno. How involved is the precedure to change this valve?

You're probably tapped for rail pressure. Try leaving your Ramifier down around 40-50%. You should see better numbers.



-Scott

 

[jwilliams3]

Or try dynoing on level 6 or less.



Level six nets the most hp unless stacked with the crazy larry program.

At least from what I can tell.

 

[strokerschmoker]

no, i didn't try less than 6 on any run, but on one of them I ran at 7/7 and about 30% of ramifier and that is where i netted 802 lbs of torque but no additional HP.

 

[robertyoke]

your cp3 may just not keep up with the fuel your are asking for and your pressure valve may be fine. I would check pressure with scan tool before buying a valve.

-robert

 

[scotty1]

Not only the Pressure relief on the Common Rail but the Cascade inside the CP3 are sometimes not functioning within spec.

I kept getting low boost and lower power then what others where and I always had heated fuel in the tank... super heated from being pressurized and sent back to the tank because of these items being out of spec.

Superduty showed me how he did a by pass between the supply and return on the CP3 to maintain fuel supply... this is what lead me to finding a solution to my problem. Not only can a properly functioning pressure box make the symptoms worse, so can too high of pressure from an aftermarket lift pump.



I was testing an Essex pump and started at 20 psi at idle thinking I was getting lots of fuel... it was working against me... I lowered it to 15 and learned over time that the volume is what is needed, not a bunch of pressure and too much volume can make the out of spec parts show their problem even more.



The by pass that Superduty came up with makes sense because if your sending fuel back to the tank and the lift pump is working overtime to supply the demand for the engine, it now can take fuel from the by pass instead of trying to draw it all from the tank... heated. Heating fuel over and over can and will diminish its quality too.

The other way around applies too. If the lift pump is supplying too much pressure and/or fuel, it can dump through the by pass and return to the tank before it gets pressurized and heated.



Perhaps pressure boxes and/or high pressure pumps can cause this but I feel that the specs of the cascade and the pop off are weak in a lot of these trucks from new and the add on components although doing a good job at what they do are working against these issues.



Scotty

 

[Tomeygun]

I too think that I have fallen victim to the relief valve. After dyno'ing on Saturday I found that the more fuel I demanded the lower the HP went. For example, I ran the TST at 7/7 and the ramifier about 65% and it made 402 HP, then TST at 7/7 and ramifier at 100% made around 370, and lastly, TST 9/9 and 100% ramifier made less HP then the two previous runs. I could not tell at all by the SOP that the valve was bleeding pressure off, but it is kind of hard to not believe the proof of the dyno. How involved is the precedure to change this valve?

Did it get smokey'er and smokey'er the higher the power levels?