Fuel pressure...Got issues.

[Paul Workman]

Last fall, I baselined my Z before doing any mods. At that time I had them run an Air Fuel chart as well, and it showed initial AF was around 12.8 up to about 3500 where it began ramping up to about 5000 (from memory) where it leveled off at 14.0:jawdrop:

So, with a top end porting done, before I ran it on the dyno again, I wanted to check out the leaning phenomenon. Sure enough, when I monitored FP at WOT, it went from 44#(?) at idle, would initially jump to 50# as I got into the accelerator, and like the AF graph predicted, the pressure began to fall off until it reached 40# where it seemed to remain steady from ~5000 to red line.

If the drop off was linear, I would say "obstruction", but the leveling off suggests (to me) some intervention is going on; regulator? fuel pump fluctuations? what?

So, the consensus of the meeting with the FBI yesterday seemed logical to me: changing the filter (easy) and work my way thru the pumps and finally the regulator. I'll letcha know what I find.:thumbsup:

One thing I don't know is what is normal for FP over rpm at WOT? Should it remain rock steady, or is there some normal fluctuation, and if so how much and what would be considered acceptable? Any more thoughts?

P.

[A26B]

Try pinching off the vacuum line to the fuel pressure regulator. It should go to max capable mechanical (fuel pump) pressure with no vacuum to the regulator.

[jonszr1]

i ck with corey on your issue and he said the following, you should have 50-55 lbs of pressure at WOT. if its less you may have a filter problem or your pumps might be getting weak, most likely the secondary pump from his experience .also ck the rubber fuel lines at the tank for cracking and sealing. hope this helps

[Paul Workman]

The trick is to keep one eye on the road, one eye on the fuel pressure gauge, and one eye on the tach...That's one too many eyes!

http://i185.photobucket.com/albums/x220/6PPC_bucket/Vettes/FPtest.jpg

I decided to push ahead; try to resolve my FP issue AND bolt on the headers this w/e. Wish me luck!

P.

[XfireZ51]

Should stay steady into the 50's at WOT.

[Jeffvette]

Change the filter. Most people forget there is one even there. Pressure should come right up. If it was a serious issue, you would be setting a fuel lean monitor code as well.