At start up no vacuum reading.

[obx tsi]

As the title states, sometimes when I start my car both my boost/vac gauge and my avcr display no vacuum. After a few minutes they both start to read about 16 inhg at idle. Also if I drive while no vacuum is showing it doesn't show any boost. Why is this? I have just recently installed a afpr that mounts to the rail, a walbro 255(I had it and just wanted it to be used rather than collecting dust), and had to put a ss fuel line from the fuel pump to the fuel rail. Around here I could not find the short fuel line from the fuel pump to the hard lines under the car, it broke when trying to remove the fuel pump. I just removed the line from my 1g part car and used it. Now I also have to crank the car twice for about five seconds before it starts. Thanks for any help.

 

[LaN-]

As the title states, sometimes when I start my car both my boost/vac gauge and my avcr display no vacuum. After a few minutes they both start to read about 16 inhg at idle. Also if I drive while no vacuum is showing it doesn't show any boost. Why is this? I have just recently installed a afpr that mounts to the rail, a walbro 255(I had it and just wanted it to be used rather than collecting dust), and had to put a ss fuel line from the fuel pump to the fuel rail. Around here I could not find the short fuel line from the fuel pump to the hard lines under the car, it broke when trying to remove the fuel pump. I just removed the line from my 1g part car and used it. Now I also have to crank the car twice for about five seconds before it starts. Thanks for any help.

Have you ran a boost leak test? Sounds like a leak to me.

 

[obx tsi]

Yes, have done a boost leak test. I have found that my throttle body shaft seals are bad. I am planning on using my 1g throttle body that I rebuilt last year but have not yet done so. Dont think that would couse the no vacuum problem though. Once when setting the base fuel pressure I had no vacuum on the line going to it. I started looking around and then the vacuum was there again. Did not think much of it them but I just remembered that happening. Could a bad fuel pressure solenoid cause such a problem?

 

[LaN-]

Yes, have done a boost leak test. I have found that my throttle body shaft seals are bad. I am planning on using my 1g throttle body that I rebuilt last year but have not yet done so. Dont think that would couse the no vacuum problem though. Once when setting the base fuel pressure I had no vacuum on the line going to it. I started looking around and then the vacuum was there again. Did not think much of it them but I just remembered that happening. Could a bad fuel pressure solenoid cause such a problem?

there is no way your car has no vacuum. it wouldn't be running. Check the vacuum Tee's there might be something blocking it.

 

[kylelilley]

What is a normal amount of Vacuum?

 

[rich3389]

17- 20 inches hg

 

[obx tsi]

I understand it should be producing vacuum but why do both my boost/vac gauge and my avcr show zero for about 1-2 minutes sometimes? I am assuming that it is something sticking closed and then opening. Do I have the gauge on the correct side of the fuel pressure solenoid? I have it teed in between the solenoid and the fpr, or should it be between the manifold and the solenoid.

 

[kylelilley]

Mine reads around 25 at idle and 20 while coasting, like if I'm going 55 and let off the trottle but stay in gear. Is this bad or too much?

 

[cbrue122]

The Tee placement might be your problem. Try placing the source for the gauge in between the manifold and solenoid. Just make sure the gauge is "seeing" what is happening in the manifold; the solenoid is more than likely causing the lag time.

 

[28-psi]

cbrue is right...tap into the vacuum line coming off the intake mani that goes to the solonoid. Common mistake...I did it too. Ive got pictures on my profile to prove it!

 

[Defiant]

Check the sensing line for a kink (or, cheap/thin hose) that's drawing closed under vacuum. The best source is the line that goes to the FPR, coming off the plenum.

 

[obx tsi]

Ok, thought I might have had it backwords. Some pictures just show the line from the manifold to the fpr, they do not show the solenoid. I thought it would be simple. Thanks cbrue122 I will switch it and see what happens. So now my question would be is that lag time normal for the solenoid? That would mean that the fpr would not be seeing vacuum at start up sometimes. Anyway thanks for the help.

 

[obx tsi]

switching the location helped. Thanks.