Ok fellas... so every road trip I have made lately I get low fuel pressure at high elevation.... here at home in LA I get 15 - 16psi ... i went up to the Rockies in Colorado... the whole time I was running 10- 12 psi...drove east towards iowa.... pressure started getting better...continued south gets better. When I get back to so. California I'm back up to 15psi... please rule out fuel filters because I had new FASS filters on it... what you all think??

very odd. 

 

Where you hauling something?  IE using more throttle to pull the long passes in CO?   Was fuel pressure lower at idle in CO? 

I've noticed that as well when I ran am airdog. It's odd and I haven't figured it out.

What kind of gauge?

wasnt pulling anything...  carrying maybe 800lbs worth of camping stuff.   my gauge is VP max .    Just idling or very low boost fuel pressure sucked...     i noticed this on two seperate trips now....    

i figured altitude had something to do with it...  but i know im not the only one up there with a FASS .....    i really need to figure this out before my next trip...  

very odd. 

 

Where you hauling something?  IE using more throttle to pull the long passes in CO?   Was fuel pressure lower at idle in CO? 

the whole time in Silverton area )south colorado  i wasnt much more than 12psi at idle  ...    fuel pressure picked up alittle once i got into iowa on I-80..  fuel pressure wasnt 100% normal til a day or two after i was home...   when i hit cali on I-10 i was back up to 13psi atleast..   i doubt fuel quality is an issue because i carried atleast 130 gallons of double filtered fuel.  

Edited August 1, 201510 yr by freedomisntfree

My guess is that the gauge and pump compensate for the altitude differently, and provided you with an indication issue.

Temperature is possible as fuel cools the pressure for electric pump typically goes down. Like start of the morning 48-55*F I show about 1 PSI lower typically. Now on my trip home from work after sitting in 105*-110*F temps the fuel pressure is about 1 PSI higher. As for altitude there is no effect on my ISSPro EV2 that I've seen.

Well I want to plug in a different gauge to rule out bad readings... maybe I can T off and install a another gauge ... i do t want to remove the one in the cab unless I have to.

Moparman... i agree with the lower temp lower pressure ... and I took that in consideration but the difference is way too much. Also the pressures were not much different while I was in Oklahoma City area 95deg. .. i will keep this thread updated. I will do another run soon... thnx for your input guys.

I would opt for a gauge check if you can see if the gauge is accurate. Air being sucked into the fuel stream might cause this issue as well.

why isn't the pressure act like it does for you engine oil start up cold higher pressure and decreases as the oil warms.