I've searched and don't see this anywhere so I'm asking. I have a 02 Cummins 3500 with 4" exhaust, quadzilla blue tooth adrenaline tuner and airdog 2 pump and a big line kit. I have the fuel pressure set at 19 psi at idle, although I may need to bump it up a little since it drops when the fuel consumption is high. It has the stock air filter box and filter and all the rest of the motor is stock. It has 72,000 miles.


I don't know what the fuel pressure should be set to. I still have the stock filter in place, but installed a Vulcan big line kit after it to the fuel pump. I installed the Quadzilla fuel pressure sensor and am reading it off of the Bluetooth gauges.


The boost pressure seems to jump around some at lower readings. For instance when looking at the digital readout, it'll be 7, then 4, then 6, then 3 then 7, all while running at steady RPM. I don't know if this is a function of wherever the sensor is reading the airflow and turbulence in the intake or if I have an air pressure leak. How do you check for boost leaks?


The quadzilla seems to bump your power setting down if it doesn't like something. For instance, if you have the EGT limiter set for 1300 F and are running power setting 8, if you really get on it, it'll drop back to power setting 6 or so momentarily if the EGT gets into the high 1100s. I think it does this so you don't get close to your setting. I have also seen it do this when the fuel pressure dips below 10. However, I've also seen it do it for no apparent reason. It's not giving a yellow light on any of the readouts so I don't know what it's doing it for.


Lastly, any recommendations for a custom tune for towing? I've been playing with 1400 stretch and 6 deg timing. I'm towing a 34' 5th wheel camper that weighs 10,000 lbs. I usually pull on power setting 4 or less. I was wondering if higher fuel stretch (like 1600) would help things, but I don't want to overheat the engine. Should the minimums be set to 0 or to 30? I'm not sure I follow why you'd want one over the other.


Any help is appreciated. I'm enjoying messing with this thing. I've built several hot gas motors over the years and pretty much know what to do with them (including a 408 stroker in a Ram SS/T). I've owned several diesels also, but haven't gotten into the programming as much. I had tunes put on my two VW's, but there's nothing to change. I had a 7.3 and 6.0 PSD, but I am a dodge man at heart.

 

I got good advice from the man at quadzilla. Also, I replaced the stock fuel filter and the spin on filter on the airdog. This seemed to help some, but it'll still drop the fuel pressure from 18 down to 10 when I get on it. I don't know why it is dropping this much. Do most folks eliminate the stock fuel filter when doing an airdog and big line kit? The man at quadzilla recommended 18 psi for the fuel pressure set point. Should I go higher?

 

Did you get your Fuel Pressure issues resolved? It almost sounds like your lift pump isn't able to keep up with the demand of fuel the VP is commanding. How old is your AirDog you are using?

 

It's an air dog 2 and it was installed brand new two months ago. He put a sump in and I removed the stock fuel filter. The fuel filter didn't have any change whatsoever, but it did make a lot more room under the hood and is one less $35 filter to change. I still will drop fuel pressure pretty low from 19 to 10 psi under WOT with the programmer turned up over setting 5. I have not changed the strainer yet, so I'm going to do that and see what that gets me.

 

Installed a fuel sump and the issue isn't as bad if you fill up at 1/4 tank (indicated). I think they bent the fuel level sender, because 1/4 tank sure takes more to fill up than it used to. And it'll run for 150 miles before you ever get to 3/4 tank.