FPR vacuum line
 

Could hooking up the vacuum line from the Fuel pressure regulator to the UIM on one of the nipples by the brake booster cause the FPR to act up and not regulate fuel properly, versus having it hooked up behidn the uim by the throttle body?

should be hook up anywhere after the TB

there a specific nipple for it on the lim

i used this source

https://www.rx7club.com/attachment.p...d=109066&stc=1

works fine for me

I doubt that's you problem, you might need a new FPR, they can go bad, you can get a FP gauge for test purposes though.

mine went bad, and had minor leak under boost only.

There is a specific nipple on the LIM to hook it up to. There are some other nipples that will work, but there are also quite a few that won't. Best to use the right one.

Dale

hmm on the LIM? i thought the stock one went to one of those right by the throttle body...guess not. I know theres a nipple on the LIM but i didnt know that went straight to the fpr.

I think this NEW fpr probably went bad cause its not releasing pressure. Like...i tried adjusting the screw on the back to let it release as much pressure as possible so its not over 80-100. and it goes down to about 40-60 and hte needle on the gauge bounces from 40 to 60. And after running my car, the too high of pressure burst the oring seals that go around the lower injectors, so they just start leaking into the motor. its happend 2 times now. I wish i saved the first o ring, the high pressure split the oring right in itself so i had 2 o rings.

do you guys think the needle bouncing is from where the vacuum line is hooked up to the uim. or from the FPR being a piece of shit. Its a SARD adjustable btw

Just a theory. I know this may sound dumb, may not. The car has been sitting for almost a year now...and...the fuel filter had about 8,000k miles on it. And it was a kragen whatever parts replacement not a mazda one.

Im thinking...maybe the fuel pressure is being released by the FPR but its going to the fuel filter which may be clogged? so its not getting back into the tank easily? so the pressure stays high. thats why the gauge is going back and forth, cause some of the pressure is making it through the fuel filter? I dont know just a thought

NM on that, i thought the return goes through the filter, my bad, but im gonna replace that anyways before i start boosting anything

40-60 psi isn't insane high pressure. The fuel injector O-rings should be able to handle that, unless the O-rings were nicked or damaged on installation.

Dale

before adjusting the pressure, at one time it shot up to 100

you are setting the base press with the vac line off right?

hmm. nooo i didnt kno that

fpr
 

I used the vacume line off of the stock secondary fuel rail for my fpr.

i think its the fpr just not letting any pressure through and letting it build up, til it burst the orings, and then the pressure drops cause its just rushing into the motor

K guys think i could have found a prob, my friend hooked up the FPR and quite possibly he could have hooked up the lines wrong...Think this could be the culprit as to why its not regulating pressure? The instructions are in jap so i have nothing to check this against, but i was reading another thread max cooper wrote and it said,

"c. stock FPR replaced with fitting on secondary rail out, flows into side port of SX FPR, second side port on SX FPR plugged
d. bottom port on SX FPR to fuel return hard pipe... continuing back to tank"

How its hooked up on mine, is the line on the right is coming off of the fuel rail, and the line on the left is the return line. Is that incorrect?

bump for anyone that uses a fpr and can tell me

fpr
 

That would be the problem. Good luck

i feel like shooting myself, cause now where do i buy the orings for the injectors!!! AHHHH i busted all 4 that i had and the dealership wants 16$ a piece for an oring

This may be of no help but the purpose of the vacuum line is to reduce fuel pressure at light loads or idle.

The vacuum pulls on the fuel pump regulator diaphram, reduces spring tension and lowers fuel pressure. You do want to make sure you are tapped in someplace where you are getting good vacuum, of course after the throttle.

When you open it up, vacuum drops, the vacuum pressure put on the regulator spring is removed, the system closes down and it lets the pump push harder, boosting your fuel pressure.

So... i should set the base with the vacuum line off to like... say 40 - 45 psi?

The book says 38psi base, I left mine at 40. Yes do this with vacuum ref line off.

Don't remember off the top of my head which line is the feed (from the tank) and which is the return fuel lines. The FSM can tell you though.

Good Luck, gald you're getting somewhere finally.

Thanks!

BTW you don't want to leave your gauge where it is currently and just swap the fuel lines to correct it. The reason is the gauge is located on the return side, not the pressure side that you want. So make sure you put the gauge on the side port too!