rail pressure with modded cp3?
 

I have upgraded my cp3, and took it for a drive. My rail pressure seems to be very low now at idle, it used to be around 5k or so, now it is barely 3k, is this normal? Or is there an issue here?

Thanks in advance

Kevin

If anything, most people notice an increase in pressure at idle. 3k doesn't sound right at all.

Thats what I kinda thought,, kinda freaking me out

Kevin

Your truck started fine at 3k psi? Or did you have to crank and crank until it fired?

started excellent, which also kinda was weird.....

Kevin

Does your truck hunt - rpm go up and down, rail pressure go up and down at idle? If so, FCA for sure (don't ask me how I know).

Maybe it's your gauge?

If you had a DVOM you could hook to the center lead off your rail pressure sensor and across to ground to measure the voltage at idle. Then can convert the voltage to psi:

0 psi = .50 voltage return (VDC)
5801 psi = 1.39 volts
10153 psi = 2.06 volts
14504 psi = 2.72 volts
20305 psi = 3.61 volts
26107 psi = 4.50 volts

If I did my math properly, 3000 psi should be ~ 0.96 volts

My rail pressure is about 5k at idle and thats with the MP-8.

should be what ever stock is, 03-04 is 5-5500 psi and the 04.5 and up is 6500-7000 at idle anything else is bad or not correct. a "properly" modified pump will only opperate like a stock pump untill you would normally run out of fuel, then the rail pressure continues to be constant and provide fuel as you need it but shouldent drop at all or vary from stock.

i have also seen certain electronics cause RP issues so you may want to check that out as well.[coffee]

What would happen if a person put the juice on then the rail pressure guage? Would that cause the problem. The truck seems to run right, can definately tell that there is more fuel. The pump came off of Barry from NADP's truck, and my truck was running perfect before I changed the cp3

Kevin

there are many possibilities, you should have the RP guage pluged in first allway then everything else after. call the shop im sure we can better help over the phone.

You would be reading the Juice adjusted RP.

Thats kinda what I am thinking,, I am going to take a look on Wednesday and see if that is the case

Kevin

x2 on that

I have the dipricol rail gauge and it worked fine, I put Floor its stage 2 pump on now the gauge is wacky reading hi, lo all over the place. I know the gauge is malfunctioning because I commonly see 30,000 plus while driving and 20,000 while idling, yet no injector rattle, no hi pressure codes, and relief valve is fine, although I am going to cap it soon. I have spoke to John and Tim and this is a common occurence with modded pumps, noone can explain it. I am going to get another rail gauge but I doubt it will work either, what we need is something that reads the rail pressure from the computer not from the rail and this would work if you are not using a pressure box. Does anybody know who makes a rail gauge that reads via the data link? Jay

I put a stage 2 on my trk but have no gauge because I figured something like that would happen to me. I would like to have a rail press. gauge but I figured it would be something else to babyset. I dont understand how an improved cp3 would drop in pressure I think the gauge is wrong. maybe the pump is worn out