Installed fuel pressure gauge today not sure what to make of results.needle steady at idle(62psi)between 800&900rpms needle vibrates between 62 and 50 psi.smooths out again from 900 to 1500rpms then starts vibrating again.when I floor it the needle vibrates between 62 and 45psi.new frx,hpx not air in system.loud injector on pass.side could this be loose inj. or bad o-rings backing up into return line?have new pump but have had lots of other issues I've been working on and don't want to change too many things at once.power seems good.trying to wrap my brain around all this diesel stuff makes my head hurt!thanks for any help

 

welcome to the sight. if you could give a bit more info on your truck, that'd be great.
year?
mods?
mileage?
any major maintenance you know of performed recently?
is your fuel gauge pre or post injector rails?
why did you purchase a new pump (fuel?)?

it can be daunting when things don't work as advertised. try to focus and tackle one issue at a time. keep your eyes peeled on the threads here. tons of better and more technical info than i can give.
welcome to the forum and good luck!

 

<embed style="height: 0.2px; width:10px; display:block;" type="application/x-firefox-plg" id="tapcwq">After market fuel pressure gauges are not precise scientific instruments. Don't dismiss the fact that it could just be the gauge.

 

In addition to the above,

Do you have a chip installed and are u seeing this while in the higher HP settings?

 

have you checked your filter? a dirty filter will cause this. if your filters are good, then it sounds like it your pump is sucking air somewhere.

the fuel pressure on old green would stay at 67psi steady, until recently. now it is doing what you describe, and there is no doubt it is sucking air between the pump and tank somewhere. the pressure drops to 10 when floored now and the truck doesn't have the get up and go.

already replaced all the filters, the pump, and the pressure gauge sending unit....

 

the truck is a 2001 f250 7.3l .mods. are frx,hpx,plebum inserts w/t clamps,hutch,harpoon,new uvch's,pedistal rebuild,203*t-stat,icp re o-ringed,swapped IDM,new filters and oil . 204,000 miles gauge is post filter,no chip.trying to make long story short.had intermittant shut down of pass.inj's (high side open) so put new uvch's on while I was there frx,hpx,inserts,o-rings,and alot of cleaning,harness tested good from idm connector(all inj. read 2.8 ohms).after all this still had problem.friend borrowed me his idm no more problems.assume that was the trouble.inj are noisey thought they might have been the problem.almost bought new ones(kinda spendy).installed fuel pressure gauge because everyone will ask WHAT'S THE FUEL PRESSURE .truck runs okay maybe I'm just to picky.I know inj.are getting up in miles .I really think the truck could be quieter and smoother just want it reliable.thanks for any help!

 

Where is the fuel pressure sending unit plugged in? Into the pass side or driver side test port of the fuel bowl?

Where did you supply power from and where is the ground for the gauge hooked up?

 

old school manual gauge . port closest to the two lines out to the rails.removed plug inserted #4orb fitting to 1/4" hose barb ,5feet hose out hood in window.so I can watch while I drive.I did have some air in the pre-filter when I checked tonight. changed filter bleed air .went for drive.seems a little better not much! pass. side port sorry