fuel pressure spec

So i hqve another post that i have code p0171 well today i went to check my fuel pressure and key on engine off it was 35psi and running at any speed in park it was a steady 25 psi. this seems low but i can not find the spec qnywhere on this board. im thinking it is way to low and replaced the fuel filter with no chnage and stqrting to think i may need a fuel pump soon!

Not sure about the Riviera but 25 does indeed seem very low. have you tried measuring fuel pressure with the vacuum line disconnected from the fuel pressure regulator ?

my my my my you must have a 96 buddy this is our year I see and ... im fighting the same code are you currently having any other codes

Yea i tried both connected and disconected. it stayed about the same which i would think would be normal as less vac would drop the pressure even more and im assuming the pressure isnt there to begin with but i may be wrong

Johnny5 wrote:

my my my my you must have a 96 buddy this is our year I see and ... im fighting the same code are you currently having any other codes

this currently is the only code i did have a camshaft positioning sensor code but that was fixed by replacing a broken wire and pin

and you haven't done nothing else to your car no mods ... have you changed any of the fuel filters?

Johnny5 wrote:

and you haven't done nothing else to your car no mods ... have you changed any of the fuel filters?

nope car is completly stock only things done are new radiator oil pan tensioner serp belts and replace broken wire to pcm but nothing performance wise also i did replace the inline filter near the compressor but didnt touch the screans on the pump

Less vacuum should increase fuel pressure, and positive pressure ( boost ) should increase it even more.

only thing I can think of is the quick fixes its a filter under the car and the one on the pump in the tank and a vuccum line that runs to the regulator

96_Juggernaut wrote:

Less vacuum should increase fuel pressure, and positive pressure ( boost ) should increase it even more.

do you have a T on the front of the supercharger or you have a single line ran str8 to the MAP

but p0171 is a lean code some extra air is coming in from somewhere you have to check the lines

Johnny5 wrote:

only thing I can think of is the quick fixes its a filter under the car and the one on the pump in the tank and a vuccum line that runs to the regulator

thats what i was thinking im leaning towards pump have you ever replaced just the pump and not the whole sending unit i found just a pump and strainer for 48 to save cash but idk if its best off replacing the whole thing

Johnny5 wrote:

but p0171 is a lean code some extra air is coming in from somewhere you have to check the lines

wouldnt too little fuel do the same?

I think a leak in a vacuum line is more common ( and cheaper ) than a faulty fuel pump. always check the cheapest fixes first

I have heard of it done but I have never seen it and not on the riv ... but look for a vacuum first

Johnny5 wrote:

96_Juggernaut wrote:

Less vacuum should increase fuel pressure, and positive pressure ( boost ) should increase it even more.

do you have a T on the front of the supercharger or you have a single line ran str8 to the MAP

the map goes to a t that has a factory plug and then anothe line going to the intake manifold

I just seen the p0171 code you put down. reason is because its having to take in more air from a vacuum line, lower intake leaking

Johnny5 wrote:

I just seen the p0171 code you put down. reason is because its having to take in more air from a vacuum line, lower intake leaking

that was my original guess but still wondering if fuel pressure has somthing to do with it 25 at idle just dont seem healty and i did try taking a can of carb cleaner and spraying around the intake and all the vac lines with no change in how its running

its not going to change how its running but you will hear an increase in engine idle it will spike that's a tricky code mines haven't came back but im spraying more gas than usual and its killing me in the pockets

Johnny5 wrote:

its not going to change how its running but you will hear an increase in engine idle it will spike that's a tricky code mines haven't came back but im spraying more gas than usual and its killing me in the pockets

thats what i should have said but there was no change in idle def is a pita code been chasing my tail the last couple weeks lol

did you spray around the lower intake and the egr valve and its piping something its under the hood if the car is starting fine

Johnny5 wrote:

did you spray around the lower intake and the egr valve and its piping something its under the hood if the car is starting fine

yea tried spraying that as well went through almos a whole can of carb cleaner lol. and it idles really nice and smooth around 500 rpm runs like a dream just the code

New update i checked fuel pressure again today and now its at almost 50 key on engine off and at idle its around 35 but the guage bounces real bad that i cant read it which seems to me to be pointing again to a fuel pump as its prolly going down when the injectors open and the fp isnt keeping up. i did also put a vac guage on the reg and it held vac and with key on engine off the fuel pressure went down with vac applied to the regulator so i know the reg is good still thinking fuel pump i thi.k im going to try to replace just the pump in the sendong unit in the next few weeks!

Find a old one in the junk yard n experiment first so u dont have no long down time in the process

If it's hitting 50 with the key off, try changing your fuel filter before you replace the pump.