No vaccum, but Ive got boost?

[Smitherines]

Hiya, I was doing my boost gauge installation today, and noticed that my gauge wasnt showing vaccum, but it shows boost, so I looked at my afpr fuel pressure gauge, and WITH the vaccum line on its at 38. Now when I installed this afpr a week ago, there was vaccum and whatnot so how could all of a sudden there be no vaccum? I pulled the afpr vaccum hose off and put my finger on the vaccum hose to see if there was vaccum, but there wasnt either. The car DOES boost though. Also, I noticed that on the TB, there is vaccum ONLY on the P connection, not on anything else. The car was at operating temperature when I tried this.

 

[Whammydill]

Where do you have your boost gauge tapped at? Personally I think the fuel presser solenoid is the most reliable place to tap the gauge

http://www.vfaq.com/mods/wayback/BradBauer/gauges/boost.html

 

[Smitherines]

Ive always had my boost gauge hooked up, it was just laying on the floor, , it always worked, so I dont understand why I have NO vaccum in the system whatsoever all of a sudden.

 

[95TalonOwner]

You must have changed something around, that is the only reason why it wouldn't be seeing any vacuum.

The fuel pressure solenoid is not technically the best place since anywhere that is connected to the intake mani is the same, it is just the easiest place and that's why most people put it there.

Check your connections.

 

[Smitherines]

A lil update here, I had to go to the doctor so I opened her up on the highway, and she everything started working right again, but after turning the car off, then back on right away, there isnt vaccum in the system...something to do with temperature?

 

[95TalonOwner]

There is still something wrong in your connections because no matter what temp whether its 0 or 200, you always have vacuum when your not boosting.

Check your connections. Connect your guage directly to the intake mani ie a port on the throttle body and see what happens.

 

[Smitherines]

Which port? Ive not changed anything, lets keep that in mind. When the car starts, it doesnt have vaccum in any other ports than "P" on the TB. Call me crazy but thats what it is. After driving it and letting the turbo push over 10lbs, the vaccum works again across all ports and the gauge registers vaccum. Its NOT the gauge.

 

[95TalonOwner]

After pushing it past ten pounds, does the vacuum work in all ports until you turn the car off?

 

[Smitherines]

Yup.

 

[95TalonOwner]

I don't know, sounds like your guage might be bad even though you say it isn't. See if you can borrow someone elses.

 

[Smitherines]

Lol listen, there is NO vaccum coming out of the fuel solenoid vaccum line, so instead of my afpr running at 28psi like its supposed to, it runs at 38psi cause theres no vaccum. Theres no vaccum in that line.

 

[95TalonOwner]

Are you hooked up to the top or bottom of the fuel solenoid? I had a problem similar to this once on a 90 eclipse, ended up being that I had it hooked up to the top of the solenoid when it really needed it hooked up to the line that goes to the bottom of the solenoid when its mounted on the firewall.

 

[Smitherines]

The afpr worked perfectly until recently, but Im adding that to the equation to further prove that it isnt my gauge. The hose that connected to the OEM fpr is now used on the afpr, which worked perfectly until recently.

 

[Smitherines]

Alright I figured it out, the fuel pressure solenoid was doing this, it only opens up at certain times, so I bypassed that and the car is running perfectly, thanks for the help 95TalonOwner!

 

[FORMONTOYA]

Sounds like you hooked up to the "secondary" side of the FPS (between the FPS and FPR), when you should have come off of the "primary" side (between the intake mani and FPS).

 

[Smitherines]

Oh...do I need the FPS? Cause its bypassed now...

 

[Auto RS T]

Sounds like you hooked up to the "secondary" side of the FPS (between the FPS and FPR), when you should have come off of the "primary" side (between the intake mani and FPS).

Ill agree with this, made the same mistake once, got the same results as smitherines.

 

[FORMONTOYA]

Oh...do I need the FPS? Cause its bypassed now...

The main function of the FPS is for hot starts.

If, lets say, you drive around in 100 degree temps. for quite some time and pull into the store to get a drink. Shut the car off and get back in about 5-10 minutes later, during this extreme temp. the fuel will "vaporise" to some extent and make it harder to start.

It's combated by the FPS.
During hot weather conditions it will open up to atmosphere and bring the fuel pressure up similar to removing the source line off the FPR. With the higher fuel pressure it's easier for the car to start as the higher pressure helps to condense and remove a portion of the "vaporisation".