i was checking my fuel pressure and its at 35 psi while the car is on? i was planning on putting on my nitrous but not no more because of this problem! i need some very good advice so give me a hand here, thanks

 

First, are you sure your gauge is accurate?

How much does it increase when you pull the vacuum line?

When was the last time you changed your fuel filter... while I doubt it is that (it would be severly starved at WOT if it is starved at idle) it is something to consider.

 

35 PSI with vacuum line connected is fairly normal.

 

it has a new fuel filter,


the guage is one of the best ones around,


i f icould remember right it didnt make a difference disconnecting the vacume line.


oh forgot to mention i have that stumble that allot of people has, heres some of the things i changed lately:

spark plugs and wires
ignition coil
fuelfilter

 

forgot to mention opti has been changed about 10,000 miles ago, but noticed theirs a vent tube on the bottom of opti and is not connected to nothing could that be a problem?

 

Assuming your car came with a vented opti that would be a huge problem. First off you would have a vac leak because the lower vent is the one connected to manifold vac via the vac harness from the intake. If you get any liquid in that vac vent your opti will fry on you.

Not knowing the year of your car if you dont have any vac line to opti you can get the whole harness at any dealer for about 25 bucks. And if thats your fuel psi with vac line connected your good to go.

 

my camaro is a 94 Lt-1 a-4 , i dont remember if the old one had a opti vent because i took it to the shop. hopfully some one who has a 94 camaro could speak out and say if theirs has an opti vent???

 

95 was the first year for vented optis, so you dont' have provisions for it on your car (basically a vent hose run to the intake elbow). My fuel pressure runs about 40 psi or so at idle...

-Shannon

 

94's all came with unvented optis and there actually more expensive than the vented ones. If I were you Id go to a dealer and tell them you want a vac harness for a 97 z28 and then just tee into a manifold vac source and the air supply for the harness comes from the elbow.There are guides on how to do this in brent frankers install and fix it guides. Sorry but I dont know how to post the link.

 

well do you think that will solve my fuel pressure problem? so your saying that the opti vent will need to be connected to a vac harness which will go to the intake elbow does that sound right? thanks allot 97 slp i apreciate the help.

 

No this wont affect fuel psi at all but it might have something to do with hes, miss, if you got any moisture in the opti.Theres two lines that come with the harness one has two check valves in it, this is the one that goes to direct manifold vac and the other line has a small 90degree elbow in it that goes into the intake elbow, this line connects to the small vent tube on the opti(top) and the other connects to the larger vent tube(bottom) and you cant get them confused because the lines are diff sizes.

 

Check your fuel pressure the correct way, then come back with the results. Start it and pull the vacuum line off. Should be 43.5psi +/-2.5psi... so anything between 41-46psi is within spec. Then hook up the vacuum line. Pressure wil drop in proportion with engine vacuum. Anywhere from 6-10psi lower, depending on cam and altitude.

Then take it for a drive and check the pressure. It should vary with throttle movement, and when you go WOT, it should return very close to the "no vacuum line" reading.

Until you have all the data, you are just wasting your time.

 

sounds good i'll let you know what happens in a few hours.

 

alright guys i checked the fuel pressure the correct way here it is:

at idle 36 psi
at idle without vac is at 46 psi

at full throttle in park 46 psi

slightly pressing the gas drops 2 psi, 35 0r 34 psi

 

TTT