I had my intake smoke tested a couple weeks ago, and found that my LH recirc valve was leaking. Also the vacuum hose to it had a leak.

 

But there was a major amount of smoke coming out of the area, and I thought something else was going on. So I started testing my vacuum lines again.

 

I found that the short 6mm hose from the left of the balance tube would not hold vacuum. It connects to a hardline on the engine, right next to the IACV/AAC, which goes to the front of the engine, then another 6mm hose connects to a hardline under the LH throttle hose, then to one of the ports marked "purge" on the carbon canister. A 4 mm hose connected to the port underneath the LH throttle plate is connected to the second hardline under the throttle tube, and goes to the port on the canister marked "Signal Vc". Then there is a 6mm hose from a 2nd port marked "purge" on the canister connected to the intercooler pipe, and one marked "Fuel" that is obviously connected to the vent line from the fuel tank.

 

The 2 purge lines will not hold a vacuum. I thought they should be sealed when the engine is off. The Signal Vc port does. The service manual says the inspection procedure is to blow air into the 2 purge ports, and it should not leak, while the Signal Vc and fuel ports should allow leaks (when blowing).

 

So the fact that my mechanic got smoke to come from this area is technically not a bad thing, right?

 

But how can one pressure test a turbo system if this is going to leak air? How much leaking by the canister is normal? When there is vacuum to the Signal Vc port does that close the purge valves or open them? Open what, they appear to be open already?

 

I guess what I am trying to get at is- how does this canister work, and how do you tell if it is borked?

 

Thanks,

 

Mark

Just loop the CC out as if you were deleting it then retest.

OK, let me put it another way, since my question isn't getting answered.

 

A Boost leak pressure test only works if the charcoal canister is removed (or the 3 system lines to it are capped).

 

Because from reading the Japanese to English translation in the service manual, the "Signal Vc" line will not hold pressure. I already determined that the "purge" lines won't hold vacuum, so they officially allow "unmetered air" into the system. So a vacuum leak there. Probably not a lot, but really, who can tell?

 

Someone conform this? If you have the factory charcoal canister still installed, can you really pressurize your intake system for 3 or 4 minutes at 5 psi?

 

Thanks...

OK, let me put it another way, since my question isn't getting answered.

 

A Boost leak pressure test only works if the charcoal canister is removed (or the 3 system lines to it are capped).

 

Because from reading the Japanese to English translation in the service manual, the "Signal Vc" line will not hold pressure. I already determined that the "purge" lines won't hold vacuum, so they officially allow "unmetered air" into the system. So a vacuum leak there. Probably not a lot, but really, who can tell?

 

Someone conform this? If you have the factory charcoal canister still installed, can you really pressurize your intake system for 3 or 4 minutes at 5 psi?

 

Thanks...

 

3 system lines? there is only 2 that run from vac points on the engine to the CC, there is a vac line that runs next to the CC lines, but this goes to your recirc dump valve on the passenger side of the car. and is the inner most (closest to the rad on the passenger side) vac tube, you can tell if you look and follow it to the front of the car, its not attached to the ones for the Carbon canister. You can remove the vac lines and bung the points it attaches too to test the rest of the system.

Maybe this will help

http://s95014253.onlinehome.us/63104/6901.html

3 system lines? there is only 2 that run from vac points on the engine to the CC, there is a vac line that runs next to the CC lines, but this goes to your recirc dump valve on the passenger side of the car. and is the inner most (closest to the rad on the passenger side) vac tube, you can tell if you look and follow it to the front of the car, its not attached to the ones for the Carbon canister. You can remove the vac lines and bung the points it attaches too to test the rest of the system.

 

There are 5 connections on the CC, but I am ignoring the fuel tank vent and the air intake hose on the bottom. The other 3 are connected to the intake system-

 

The purge line that goes to the balance tube

The vacuum signal line to the LH throttle body (right under the boost hose)

The third is the purge line that goes directly to the air intake tube right above the canister (also a vacuum port, even when the car is boosting as it is before the turbo).

 

This is what is leading to my belief is that anyone who can hold pressure in their intake system for more than 2 seconds MUST have these three nipples capped.

 

z32bolt- I have that page open as one of the 25 open tabs in my browser that I am going through trying to find my answer.

As far as I'm aware it's not supposed to hold pressure, it's not a leak down test it's a test if it's ability to hold air at a set passage. You need a good compressor and apply 5psi of air to be passing through the system air will be being lost through the combustion chambers during the process as well. If you can hear a leak but not pinpoint it then get some soapy water and a brush and apply it to the area carefully, the bubbles will pinpoint the issue extremly accurately.

As you probably know, the CC has no purpose whatsoever other than to recycle fuel tank fumes. If it becomes a source of vac leaks, it's simply discarded as it doesn't affect our emission testing over here. Unless of course the car is being kept 100% standard intentionally, no one is going to spend time investigating a 25yr old plastic can. Along with the AIVs, the PRVR and the EGR system, the CC should be removed/bypassed at the earliest opportunity on these cars. Even standard cats have one positive going for them, and that is because replacement decats can possibly accelerate rear turbo oil seal wear.

 

Regarding boost leak tests, my car has been pressurised to 22psi without issue.