Dan Marino

Got my truck finally running tonight after pretty much modifying every portion of the kit except the electronics to the dual pump kit.

One thing that I noticed was a different sound coming from the engine. Its hard to explain but it sounds like a sucking noise from the top of the motor. Above the head where valves are positioned. Its in pulses. I have checked everything that i know of - but everything is tight and where it should be. I was wondering if the rail is fed by the high pressure line in pulses or is it a constant flow through the high feed lines? The high pressure line comming from top CP3 that feeds rail has a pulse type of feeling going through it when you hold your hand on it...and the pulse hits the same time as the sucking noise.

Also -I was seeing 7500 on rail pressure at idle with stage II pump and Air dog - then tonight (before we sprung a leak on the rail pressure sensor) the rail presure was only 5000 at idle. What is normal rail pressure with dual pumps at idle? I figured it would stay around 7-7500.

lmills

03 motors should idle around 5500-5800 PSI

Dan Marino

so why did I see 7500 before?

lmills

sometimes, they do run a little higher when cold, or the return line could be restricted and not returning enough fuel, or the fuel inlet pressure could be too high. All these will cause that issue

Dan Marino

I have to rework fuel pressure gauge because of new airdog - so not sure about it yet. as far as return we have a fairly large sweep in the 3/8 line from top cp3 to the rail - so I am pretty sure its not that. Other return is the stock return that was always used.

Anyway, do you know if the rail is fed by the pumps in pulses -rather than a constant flow?

ramtd02

the pumps are a piston pump.....so yes the rail will be fed in pulses. There are 3 pistons per cp3. What is probably happening now with the duals is both pumps are pumping at the exact same moment amplifying the pulse sound?

Dan Marino

I thought this was the case but didnt know for sure. When I put my hand on the metal high pressure feed line - I can feel a pulse going through it and the 'new noise' is in time with it. It was startling at first becasue I had never heard anything like it before. Another poster named Jared900rr who posts on here just installed dual pumps and he said he has no 'new noises'. So I am a little concerned.