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Discussion Starter #1 (Edited)
Boost/vac issue with EBC

Just last night my 89T had a hiccup again. This time possibly more expensive than the last. The ProfecB suddenly stopped reading vaccum, so I parked it. This morning I took it for a drive again and as I'm watching the boost gauge climb, the EBC is still stuck at 0!!!! Went to check codes and guess what I got... Code 34: Turbocharger Pressure Signal. Everything with the EBC is installed per the installation manual. It was working fine one minute then just stopped and now a code 34 is showing. Anyone have this happen before?? I'm hoping it's soemhting simple, but so far it doesn't seem so. I've checked, rechecked, and checked the routing of the lines from the Profec B to the Valve unit to the turbo and actuator. Also checked from ProfecB, to the vaccum from FPR. Nothing seems to be out of place or wrong with either. It just simply won't read and it's causing the boost to continue to build. I really need some insight with this.
 

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all vacuum lines dealing with the EBc are brand new as of now. it's still not registering anything. I took lines apart and blew into them with it attached to EBC and it takes a lotta air to register anything. AFPR acts the same with vacuum line plugged or unplugged. absolutely no change in FP. The filter for the ProfecB looks brand new and has little resistance when blowing through it. All lines are in tact and are brand new dealing with the EBC. I'm throwing the code 34: Turbocharger pressure signal. but it's funny because both the stock gauge and the one I put in are registering both boost and vacuum. Both are functioning what appears to be normal.

I'm stumped. i checked the resistor solenoid and it checks out at 3 ohms like TSRM says. Haven't found how to check pressure assy located right next to it. Hoping it's something simple but I'm lost as of now.

anyone have any advice or wisdom to share??
 

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The vaccum line that goes to the fuel pressure regulator goes through a vacuum switching valve before coming from the intake manifold. If the vacuum switching valve is stuck closed your regulator and the ebc pressure sensor would not be seeing boost\vacuum. The switching valve is only suppose to be closed when the engine is hot and for a limited amount of time after cranking the vehicle. So, try bypassing the switching valve temporarily or permanently.
 

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The vaccum line that goes to the fuel pressure regulator goes through a vacuum switching valve before coming from the intake manifold. If the vacuum switching valve is stuck closed your regulator and the ebc pressure sensor would not be seeing boost\vacuum. The switching valve is only suppose to be closed when the engine is hot and for a limited amount of time after cranking the vehicle. So, try bypassing the switching valve temporarily or permanently.
Is this the switching valve that's located on the Thermostat? If so the prongs are broken on mine and it has been bypassed. If it's not the valve you're talking about then where is it located? I'm drawing a blank right now. I can go out and check all the lines in the morning. I'm hoping this is the problem and it's easily fixed. Everythign was working fine at first then just stopped.
 

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The vaccum line that goes to the fuel pressure regulator goes through a vacuum switching valve before coming from the intake manifold. If the vacuum switching valve is stuck closed your regulator and the ebc pressure sensor would not be seeing boost\vacuum. The switching valve is only suppose to be closed when the engine is hot and for a limited amount of time after cranking the vehicle. So, try bypassing the switching valve temporarily or permanently.
Looks like its vsv 25860 is that correct? What is the reason for closing it? Meaning why is it there to do what it does, what is its job?



http://www.cygnusx1.net/Supra/TechTips/graphics/vacuum_2h.gif
 

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From what I've read on the forums when you start your car when it's hot it prevents the vaccum of the engine from lowering the fuel pressure like it usually does. When the fuel pressure is higher there is less chance of it turning into a vapor in the fuel lines(which is bad). The higher the pressure the boiling point of the fuel is raised.
Some people who get rid of this say the car can be difficult to crank when it is hot.
Most people running aftermarket fpr s don't use the vsv.
 

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I checked the VSV and the vacuum, line going from AFPR to it was blown off. Plugged it back in and everything worked great! EBC reads vacuum an I will test the boost out later. I have a few feet of extra vacuum line and I'm thinking about bypassing the VSV like you mentioned if the problem keeps up. thanks for the help guys. I really appreciate it.
 

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well under boost it blew off again. I replaced it with a new hose taht was a tad shorter and it has yet to blow off!! It's holding strong but my boost is now limited to 15psi, which is fine by me. Just need to set the EBC and get the tune tomorrow and it's off to 2K9 for me!! Hopefully with 400+ pushing me!! no more probs are showing as of now. Just needs the tune tomorrow. And I've been told Justin is the best of the best at Boost Logic/Tuning Concepts.
 
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