Yes I meant the actual pump itself. I do agree with you that after the fuel leaves the pump other mods would definately affect fuel rail pressure. I should have worded that a little different, but you make a very good point. Not to hi-jack this thread, but has anyone had problems with the fuel rail leaking while using a pressure box? This is the second time I have had to take my truck back in because the fuel rail is leaking.

 

It is possible that the increased pressure with the pressure box is more likely to find weak spots and areas that are not sealed 100%

As for the pressure being the same with or without modded injectors, then you would be refering to dead-head pressure? Where you would be checking to see what max pressures would be that it could obtain?

 

Thank you.

 

I'm not sure some of you guys are getting this. The ONLY comparable number would be flow rate of the cp3. You cannot compare a stage 1 to a stage 3 by rail pressure. You can, however, monitor rail pressure to determine if you need a larger flow rate. So here is a scenario...

Stock truck
Checking rail pressure I find max pressure to be 22kpsi.
Now I add some type of programmer or box.
Checking rail pressure I find max pressure to be 17kpsi.
The truck is still calling for at least 22kpsi (maybe more depending on the box)
Therefore, my stock pump does not flow enough fuel to meet the demand.
I add a stage 1 pump.
The stage 1 pump flows enough fuel that now my rail pressure is back to 22kpsi - what the truck is calling for.
I decide I want to make my stage 1 a stage 3. My rail pressure stays at 22kpsi - why? Because that's all the truck is calling for. It doesn't matter if the flow rate of the stage 3 is more, whatever is not needed is bypassed.
So now let's say that I have a box with pressure that calls for 25kpsi. If I have a pump that flows "x" and that will only sustain 24kpsi, and now I add injectors what happens? The flow rate of the pump did not change, it is still "x". The hole size in the injector nozzle has changed, however, and now the same amount of fuel (flow "x") is passing through less of a restriction. My rail pressure is now lower than before simply because of the injectors.

So the boxes/downloaders/injectors/lift pumps/etc. do play a part in rail pressure. I promise that not everyone with a stage 2 II pump has the same rail pressure. The only comparable number is the flow rate. The only way to know what flow rate you require is to know your mods, know your rail pressure, and take the advice of someone that knows these pumps inside and out and what kind of flow might be needed to support your mods.

 

Yes that is what I am thinking also. I would like to know the different flow rates that the pumps produce in the different stages say versus the DIY mod and compare them all to a stock cp3 pump. Any mod you do to the engine is going to change "fuel rail" pressure but it will not change the flow characteristics of the cp3. That pump is going to produce the same amount of flow whether you have Stage I or III sticks in that motor or a box that ups fuel pressure or changes duration. I know we need more fuel to keep fuel rail pressure up, but it seems like a lot of money for something that only flows 20-30% more than stock. Oh well, you play, you pay I am sure when I go to replace my cp3 I will be getting a modded one I just have to get the truck paid for first, then I can start spending money on mods LOL.

 

Good info.

First, I defer to your last sentence.

Then re: rail pressure,.... demand is 19.7k with my setup and with sticks and one downloader. Actual to support the 19.7k demand is 16.8k. That varied by only 5k psi on the same type of run but without the downloader and just the sticks,... not much difference in my view. My actual dropped to 5k psi twice on each run whether with or without the downloader and one of those times was the infamous defueling but the other crash and burn the demand was still at 19.7k when the rail pressure came crashing down to 5k psi!! It's hard for a non expert on cp3s like myself to think that this is suppose to happen. Further,.... why on any run with any poweradder is the actual at least 2k below the demand on a modded pump? That too doesn't seem to be right to me.

Thoughts,... anyone?????????

 

Does anybody know if the line going into the fuel rail from the pump has a seal or washer where it attaches to the fuel rail? Just curious, I would fix it myself if I knew I could just replace a seal. It looks like just a brass nut. I broke it loose and retightened it but it is still leaking. I hate taking it to the dealership, sometimes i think they do more damage than good.

 

lmills, yes you are correct, I was referring to the dead head pressure of the cp3 unit itself.

 

Got my response. Customer Service is alive and well unfortunately not with the company who sold me the lvl 2 cp3. I got a phone call from their competitor and we had a long detailed discussion. They agree, "there is a problem". It most probably is a bad fca. They are going to test it and tear it down and repair as necessary. Happy ending.

Tks to you all who have assisted.

 

Sometimes I just want to bang my head into a bridge abutment!!

 

OT - in response to your original query, the stock CP3 on my '05 develops 5-7K psi at idle, and 22.5K psi max at WOT - all with stock fueling.

Everyone remember that it's neither a matter of only pressure or flow rate.
The relationship is: Pressure X Velocity = Volume

I think it would be great if the manufacturers would publish the actual volume of fuel delivered by the modded pumps, rated at so many GPH at a certain RPM. Doesn't the FSM have those specs listed for diagnostic purposes?

 

OT...

pm me sometime about the pump.

Thanks.

 

Done. Ck your PMs.