Truck seems to be falling off at WOT between 75-78 MPH on up...the idle Fuel Pres. is 61psi. from a roll at 35 to 100mph it falls down to as low as 50 and climbs no higher than 55 through-out the run up to 100-110mph. everything else seems to be reading normal Timing during the run falls back to 9 deg. run was done at 50 deg. ambient, boost was running 7.6 lbs. Truck pulls VERY hard up to about 70-75 or so. Can anyone tell me if the fuel pres. is within spec.

Thank You
Mark

 

It should never go any lower than 58 psi.

 

moregrip,
it never got over 55, would 3 lbs to 8 lbs make a big differance. Also this is the fuel pump that came with the Radix kit which only has a couple thousand miles on it.
Mark

 

When is the last time you changed the fuel filter? First place I would look.

Jody

 

Do you have a "Z" in your vin? My pressure never goes over 62 and drops to 48-52 at idle. I have the inline 255lph pump as well. The "Z" would mean you have a flex fuel truck, the fuel systems in those are all screwed up.

 

1slow, No "Z" My fuel pressure is 61 at idle and than drops down under WOT.

Fuel filter was change when the Radix was installed, about 2000 to 3000 miles ago. I would have to check my records.

I guess I will have to call Brian On Monday, or maybe he will chime in on the forum.
Thanks guys for you input.
Mark

 

Maybe swap the FPR. They are pretty cheap and easy to swap. I hear they can go bad for no reason, just go bad.....
Is this a recent issue or has it been this way since the radix install?

 

1Slow, Sorry I have to ask What is a FPR? fuel pressure regulator? Where is it located?
It started after Radix install. I was doing other Mods when this problem started so I thought the problem was caused by them, until somebody suggested I do a fuel pressure test. For a couple of months I kept telling him it can't be the fuel pump its updated and brand new. Finally he said just because it is new doesn't mean it is working properly. So that leaves me to where I am today.
Thanks
Mark

 

Yes the fuel pressure reg. Should be on the drivers side, rear part of the Radix. It will be bronze/gold colored and have may have a vacuum line attached to it. Some years are vac/boost referenced and some are not.

 

Is there a way to tell if it is bad or should I just replace it. So you think this is something I should do before I drop my tank and replace fuel pump.Also If I replace the FPR would I just go to the parts store and ask for one for my year and make of truck or is it differant because of the Radix? I heard you can get an adjustable one. Is that a good Idea?
EDIT: I have nothing located where yours is I don't have that bronze or gold thing where yours is.
Thanks for your help 1slow
Mark