FPR problems - need some advice

[soldave]

Have been trying to diagnose a rich idle problem this evening and I worked my way to my Sard FPR. Checked vacuum lines for any tears or cuts (didn't see any from first glance), and then set to work on checking the fuel pressure. Pulled the vacuum line off and surprisingly the fuel pressure jumped up to about 50psi (it should be 42.5psi on the early Evos). Thought I'd found my problem so I blocked the vacuum line with my thumb, loosened the locking nut and turned the adjusting nut anticlockwise. Pressure dropped to 45psi, but then wouldn't drop any further. I even removed the top elbow fitting that the vacuum line would go into and it still wouldn't drop below 45psi.

So I thought "What the hell..." and decided 45psi was good for now, so I tightened up the locking nut. Put the vacuum hose on and watched for the fuel pressure to drop as it should do. But there was absolutely no movement in the fuel pressure needle when the hose was connected.

Any ideas? Am thinking either the FPR has a problem with it or I'm just inept and there's a big vacuum leak somewhere along the line.

 

[carbide]

Sounds like your AFPR can only go down so far! I would suggest getting a different one that can actually turn down the fuel pressure, like an Aeromotive! On my 1G, under vaccum its at roughly 28psi at idle (which is like 36 without vaccum).

 

[BlueTurboSpyder]

I agree that its sounds like your fpr is bad. It's not unheard of for the diaphrams in some brands go bad fairly easily but I'm not too familiar with that particular brand. I had a fpr that refused to be turned down past 55 psi once and I had to purchase a new one. Go with an aeromotive or fuel lab fpr if you have the funds and you'll never have that problem again. If you don't have the money right now but have something like a piggyback and a logger in your car than you could also tune it out. Good luck.

 

[luv2rallye]

Pulled the vacuum line off and surprisingly the fuel pressure jumped up to about 50psi

fpr w/o vacuum line is supposed to raise fp to avoid vapor lock on starts (this normally done by fuel pressure solinoid): http://www.dsmtuners.com/forums/problem-diagnosis/217349-vapor-lock-hot-start.html

 

[qnz]

fpr without vac is supposed to be lower.

I have a sard FPR as well. It does not read below 50psi. I was told I have the intake and return lines backwards, from a sales rep. That the fuel in should be on the bottom and return is the port on the front.

I swapped them to check and still not change. It does not go lower than 50 still and when raising the pressure, it jumped from 53 to 100 so im pretty sure the fuel in is not on the bottom.

Also, I thought the sard FPR was supposedto be a rising rate FPR. In boost, my fuel pressure does not fluctuate more than 2 psi, if at all.