alright i just finished installing my new Defi boost gauge on the A pillar. This is my problem..first when i turned on the engine...everything is working fine..took it for a test drive...PSI and vacuum is working fine..then till i turned off the car..and turned it back on..the Vacuum is at 0 and when i drive it the PSI is only working not the vacuum..then after a short period of time..the vacuum drops down to 20 and works fine..im not sure but could it be the boost gauge itself? or is the hose just pinching somewhere??

 

Sorry no help here, but I'm experiencing the same thing with my Defi BF gauges, Seems like the problem only occur when the motor is hot or driving it hard. I've checked all the vacuum and they look fine.

 

yes exactly..only when the motor is cold, the gauge hits the vacuum...i think its the gauge maybe during the shipment?? or i dont know..

 

Its normal man.Ive got Defi Dgauge boost and EGT and the boost does that everytime on start up for me 2. If you hooked into the vac line on the fpr then I was told thats why it does it and since its such a long line from the fpr to the gauge.Hope that helps!

 

Relax, it's not your gauge. Sometimes in order to maintain higher fuel pressure at start-up the ecu will hold vacuum until the desired fuel pressure is met. Then normal vacuum resumes. There's nothing wrong with your gauge, or your car. If your car starts doing it for more than about 20-30 seconds after starting the engine you might have cause to worry, but I presume yours is just like mine and everyone elses...

 

My d gauge always works for both vacuum and boost regardles of temp. When I turn on the car it stay at 0 for maybe 1-2 sec and then goes to about 20in of vacuum. it has never acted up.

 

You tapped the boost source in the wrong place. You should tap a vacuum line right off the intake manifold. If you did the FPR line, it needs to be before the fuel pressure solenoid. That solenoid will close during hot starts to keep fuel from vaporizing in the fuel rail.

And dude, our cars do not hold vacuum at anything when the car is hot. Vacuum is always the same, regardless of temps or startup. Vacuum is just prevented from going to the FPR in order to keep the pressure higher in the fuel rail.

 

Happens to me too, once in a while...when the car is hot...no worries...

 

That's not true. My gauges always read vaccum. As has already been said, you tapped the wrong source for your boost pressure.

 

I dont know what you are talking about. I have had no problems.

 

Bingo. If you tapped the right place, you'll never have this problem.

 

Hmmmm.......I guess he knows more than DEFI since they say to tap it into the vac line running to the fpr........hmmmmmm.........must be nice or maybe he doesnt know why Defi says to do it that way.....Ill go with the later!......lol

 

Who said he tapped the FPR line? Did he? What he is decribing is indicitive of tapping the wrong source, probably after the FPR. Don't believe me? Fine.
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Just a quick search shows that others have reported the same problem and the answer is always the same. There is no reason for the gauge not to read vacuum if it is tapped into the correct source (before the FPR).

 

Mine is tapped before the FPR and there is no problem. At start up it takes a second to drop, but only a second.

What is odd is that I hooked up NOVA EVO's gauge and tapped the same line; so it may be some of the Defi gauges. I've used the same source on no less then 7 evos and they all seem to be perfect.

NOVA, next time we get together I want to see that happen. Not that I doubt you; I've just never seen or heard of it doing that.

Good Luck!!

 

Man, you have no idea what you are talking about. The correct place to get it is anywhere directly off the intake manifold. The FPR line happens to be the easiest. But, there is a solenoid (FPS) also on that line. You have to tap before the FPS (still on the FPR line) to get it to always work correctly.

Hooking up a boost/vacuum gauge isn't rocket science. If you tap into any line coming directly off the intake manifold (like the FPR line), you have a good source, as long as its a straight tap into the manifold.