intake to fpr vacuum question

[eds56]

hello all,
hope this hasn't been answered somewhere else, i tried searching for it.

is the vacuum line from the intake to fpr supposed to be full engine vacuum? if i leave the line connected, it causes a severe idle fluctuation, almost to the point of stalling. if i disconnect the line, the idle stabilizes. i can't close-off this intake port vacuum without the engine stalling out completely. i also noticed the return line gets as hard as a rock when the vac line is connected. i disconnected the return line and blew through it. i had some resistance, but could hear the air entering the tank so it is not plugged. i have tested all of the other components as per the bentley manual. new fp, fpr, fuel filter, intake gasket. car does smell like it is running rich. struggling bad here, help please!!

'88 ix, 5sp

[Madhatter]

It needs a vacuum supply to move diaphragm inside and alter fuel pressure under load, it's normally from a hose run to the other side of the inlet manifold (one of the ports on the exhaust side). If it's causing idle issues when you connect up the vacuum line; 1) make sure it's actually vacuum. If you take the line off when running you should feel a little vacuum sucking on your finger when you place it over the hose; and 2) make sure the fuel reg isn't leaking. When they fail they often leak internally and send raw fuel through the vacuum line and into the manifold.

[eds56]

Hat,
thanks for the reply. i have the vac line connected to the factory intake port. i do have consderable vacuum there. my manometer pegged at -200inwc (about -.5 bar) is this too much? it sure seems like it to me.
i fabbed up a vacuum line breather tee arrangement and installed it in the line. the car runs much better with it in, i just don't want to drive it half-a$$ed like that. still looking for help.

[jlevie]

With the described symptoms. I'd suspect a bad FPR/

[eds56]

lev,
that was my initial thought also. i have 2 used ones that act the same way. i just put this engine in, so i have no database on how it acted in the donor vehicle.

[jlevie]

Get a brand new OE/OEM FPR. And run a rail pressure check with the engine running. With the vacuum line connected you should ~38psi with the throttle closed and ~43psi with the throttle open and the engine at or above 2500rpm.

[eds56]

PROBLEM SOLVED!!!
Good call on the rail pressure check Lev. Initial hook-up, engine running with vac line connected yielded 57psi!!! I then disconnected the return line and ran it into a gas can, voilia! Pressure dropped to 35psi.
I then disconnected the return line from the fpr and the tank and blew compressed air through it. Small pieces of debris came flying out. Lastly I blew a couple short bursts through the steel line on the tank(with gas cap off I might add) and reconnected all the lines.
Car runs perfect with 35psi at idle, 40psi @ 2500ish rpms!
Happy camper, thanks to all!