well this is a simple question that i hope will get my car back on the road

i need to know where the vacuum line is tht controls the fuel pressure regulator i have good fuel pressure (45psi) when the return line is clamped off and bad pressure (30-35psi) with the line free
i was talking to a friend of mine and he suggested the vacuum control line may be suspect but im not sure where it is

i have been geting SES light for a while with a code that says i have a vacuum leak so i want to check this out before i replace parts

as always thanks for all your help

quote Originally posted by serealport: i need to know where the vacuum line is tht controls the fuel pressure regulator

Do you presently not have a vacuum line running to the fuel pressure regulator?

In the factory setup, the vacuum line is connected to the forward side of the regulator (which is by the distributor).

quote Originally posted by serealport: ...i have good fuel pressure (45psi) when the return line is clamped off and bad pressure (30-35psi) with the line free

Is that with the engine stopped or running? Those are normal gauge pressures when the engine is running. The purpose of the fuel pressure regulator is to maintain a constant fuel pressure across the injectors, i.e. a constant pressure differential between pressurized fuel and manifold vacuum. Since a fuel pressure gauge measures pressure with respect to constant atmospheric pressure, the gauge pressure will fluctuate up and down with changes in manifold pressure.

If you're measuring only 30 to 35 psi with the engine not running, then there could be a problem with the pressure regulator or the pump itself, or the fuel filter could be partially clogged. I really recommend not clamping the fuel return line shut; besides possibly damaging the hose itself, it could also possibly cause damage to the fuel pump or pulsator (if one is still installed) due to overpressure.

[This message has been edited by Marvin McInnis (edited 06-18-2009).]

umm i dont know

i know that i have a vacuum line on the egr valve and i have vacuum lines on the red part (part that says fiero for v6) of the intake manifold near the dist. one near the fuel pressure reg. and one that is on the bottom of the black electrical thing (dont know what it is or does) near the fuel pressure reg.

jim said that if i pull the vacuum line off of the reg. (not sure which line that is) then it should let the pressure go up to 45 or so im not sure what he is talking about does this make sense to you guys

also i started the engine and let it run while i pulled of different tubes to see what happened the one on the egr valve didnt seem to affect the idle nor the ones near the pressure reg. but the one near the dist. cap on the manifold seemed to make the engine run at a higher rpm for about 5-10 seconds
and the car would not stay running it started good the dwindled and died(about 2min) . i started it again and it started off bad and then died (about 20 sec)

i read that the catalytic converter can clog and cause symptoms like this but i dont know enough about cars to tell if the cat is messed up it looks to have some pretty cruddy welds on it so i dont think it is original it also has a tube sticking out of it with a small hold (maybe 1/16") drilled in it and yellowish deposits very pale faint yellow

if any of this sound familiar to you please let me know im starting to miss my car =( thanks

The vacuum line for the fuel pressure regulator is the same one that connects the MAP sensor. There is a T in the line where one side goes to the MAP and one side goes to the FPR.

okay when i run the car i get about 35 psi when i take the vacuum line off i get about 40 psi but the car does not stay runing

The fuel vacuum line has nothing to do with the upper manifold vacuum line. The right vacuum line comes from the black dome thing with 6 torque screws that sits on the fuel rail. This is the fuel regulator shown in the picture above. The line then goes around to the thermostat side and enters a boot just off and below the map sensor- the black square/rectangle thing next to the thermostat housing.

I believe stock pressure for our cars is around 43psi. I'm not sure how you are reading the pressure because you need a gauge off the fuel rail. I have the holley adjustable fuel regulator on mine and it say to set the pressure with the vacuum line off which would be disconnected off the regulator and not the map sensor area. I had a check engine light come on when the vacuum line came off in the map area.. My pressure is set at 4o psi with no vacuum and when I do hook it back up to vacuum, my pressure goes to around 32 psi... I'm running a 3.4L block though..

try running the car, take the vacuum line off and plug the line once you remove it from the regulator.

ive been reading about cat converters and the symptoms sound like what my car is doing

if i have a clogged cat could that cause low fuel pressure?
EDIT:

quote Originally posted by greasemonke50613: try running the car, take the vacuum line off and plug the line once you remove it from the regulator.

i read your comment so i started the car and pulled the line from the manifold but not from FPR or MAP and coverd the line with my finger and the manifold with other finger and the pressure was up around 45 psi but the engine died anyway

dont know what this means but i hope it helps

[This message has been edited by serealport (edited 06-19-2009).]

quote Originally posted by unboundmo: The fuel vacuum line has nothing to do with the upper manifold vacuum line.

Huh?

I don't understand what you're saying. The description as stated by Hudini correctly describes how the vacuum line is connected to my fuel pressue regulator and others I've seen. If yours is different I suspect it's been altered.

quote Originally posted by Hudini: The vacuum line for the fuel pressure regulator is the same one that connects the MAP sensor. There is a T in the line where one side goes to the MAP and one side goes to the FPR.

It sounded like he was pulling the wrong vacuum line off in this statement..... so I was explaining which one

----quote

""jim said that if i pull the vacuum line off of the reg. (not sure which line that is) then it should let the pressure go up to 45 or so im not sure what he is talking about does this make sense to you guys

also i started the engine and let it run while i pulled of different tubes to see what happened the one on the egr valve didnt seem to affect the idle nor the ones near the pressure reg. but the one near the dist. cap on the manifold seemed to make the engine run at a higher rpm for about 5-10 seconds
and the car would not stay running it started good the dwindled and died(about 2min) . i started it again and it started off bad and then died (about 20 sec)""

quote Originally posted by serealport: okay when i run the car i get about 35 psi when i take the vacuum line off i get about 40 psi but the car does not stay runing

I'd say your fuel pressure is fine. You've got other issues. When I measured my fuel pressure, this is what I got:

Fuel pressure with key on/engine not running is 41 psi.

With the engine running at idle it's 33 psi.

My GT runs fine with this fuel pressure.

quote Originally posted by serealport: ive been reading about cat converters and the symptoms sound like what my car is doing if i have a clogged cat could that cause low fuel pressure?

I'd say "No".

A clogged cat will usually allow a car to run, however there's no power over 3000 RPM or so. My experience with a clogged cat was reported Here.

quote Originally posted by Patrick: I'd say "No". A clogged cat will usually allow a car to run, however there's no power over 3000 RPM or so. My experience with a clogged cat was reported Here.

this is what happend for about a week or two if you tried to gas it above 3k then it would just kinda cough at you then it started getting worse and in about 30 min of driving it went from no power and not ovre 3k to not getting over 1.5k and i couldent get the car to go over 10 mph or so
now if its cold it will run okay for about a min then it will be bad and not rev up if its hot when you start it then its just wont rev up and usually dies in a minute or so

thanks for the feed back

quote Originally posted by serealport: this is what happend for about a week or two if you tried to gas it above 3k then it would just kinda cough at you then it started getting worse and in about 30 min of driving it went from no power and not ovre 3k to not getting over 1.5k and i couldent get the car to go over 10 mph or so now if its cold it will run okay for about a min then it will be bad and not rev up if its hot when you start it then its just wont rev up and usually dies in a minute or so

When my cat clogged up, the elevated engine bay temperatures cooked my ignition module (as initially reported Here).

If you suspect the cat you could remove the O2 sensor to see if it makes a difference. Don't run it for long like that as raw exhaust is coming into the engine compartment. From what I've read so far it sounds like your fuel pressure is normal.

quote Originally posted by Hudini: From what I've read so far it sounds like your fuel pressure is normal.

well that is good that is kinda what Patrick said now im wondering what is the problem

i am going to try the o2 sensor and be right back

quote Originally posted by serealport: i am going to try the o2 sensor and be right back

I believe a Fiero will run even without an O2 sensor. [EDIT] Okay, I see what you're doing. You're going to remove it to see if the reduced exhaust pressure helps. Got it!

If it's not a clogged cat issue... When your Fiero cuts out, how about checking for spark while it's being cranked over.

[This message has been edited by Patrick (edited 06-19-2009).]

i pulled the o2 sensor and it started and seemed to run better im going to put the sensor back in when it cools off and try it

It doesn't take an "wreck" to plug a cat. **** just happens.

I think it's high time you had a look in your cat. If you looked at the link I supplied earlier, you now know what a plugged cat looks like.

If nothing else, at least disconnect the downpipe from the cat and start it up to see how the engine runs.

the wreck was my fault so even if i could prove that it was caused by the wreck i would still have to pay for it (insurance =liability only)

guess it is time to bust out the sawzall everything that could be welded in on this pipe is
when i put the exhaust back together should i weld the cat in or just clamp it im not to concerned about performance i just want to know what is best for the long run

also any suggestions on which cat to buy ( inexpensive is good) or any thing that i should avoid

[This message has been edited by serealport (edited 06-21-2009).]

quote Originally posted by serealport: should i weld the cat in or just clamp it

Welding is probably the best, but it sure makes it difficult to take apart when cat replacement is required again!

BTW happy fathers day to all dads

i figure what ill probably get after that tomorrow or wed ant look at cleaning it out then but i am probably going to replace it

thanks to all for the suggestions and tips