SpeedRacer

Ok, so I used my Haynes manual to determine that my purge control valve isn't working. I'm not getting vacuum from it until about 2800rpms, and there is supposed to be vaccum(from the nipple that has the line on it that attaches to the oil filler neck) at 2000rpms. I have been told this might be the cause of my blue smoke at startup(sometimes) Well my question is..what is the purpose of the Purge Control Valve? I followed the lines on it and it appears to use vaccum createt by air rushing through the expansion chamber, and using this vacuum to pull oil from the oil filler neck and then the oil travels back to the expansion chamber? Is this correct? And if so, WHY? What would happen if I removed the PCV?

SpeedRacer

Does anybody know ANYTHING about the purge control valve?

Icemark

Purge control valve is basicly the same thing as a PVC valve on any other car. It allows the crankcase to vent its fumes into the intake trac of the vehicle.

If it was stuck open it might cause the smoke on startup, but thats iffy. I would guess the oil is leaking past the seals in the motor before the PCV.

Ask Irv, Keiths dad, I thought he was very strong on this topic.

Six Rotors

iTrader: (17)

The purge valve allows for the removal of gas fumes trapped in the charcoal cannister and engine blow by gas to the intake when the engine is running and the throttle is open.If you didn't have the purge valve there the idle would be screwed up because of unmonitored airflow.The way the purge valve works is that it closes the passage to the oil filler neck at idle,then when you open the throttle(as at 2000rpm)the passage is opened.The small quantity of fumes pulled from the engine and charcoal cannister are small relative to the total airflow and do not affect engine operation.
I saw the post referring to the purge valve being the source of oil in the throttlebody causing smoke on start up.I sort of disagree.Obviously some small quantity of oil vapour is sucked in there when the purge valve does its thing but not enough to make blue smoke on start up.You would have huge oil consumption before there was enough blow by.I would look somewhere else.One thing you can try is allowing the motor to idle for a couple of minutes before you shut it off--particularly if you have been driving hard.This allows oil to drain from the rotors into the sump rather than past the oil rings into the rotor space.

SpeedRacer

Thanks for the info guys...I've checked my compression and it seems fine( around 90psi on all 3 sides of both rotors)...strangely enough I haven't seen blue smoke in about a week now. It was starting to do it every day for awhile and sometimes it was pretty bad, enough to scare me into thinking I was gonna need a rebuild. I really doubt oil is leaking past the seals. What else besides oil leaking past the seals could cause an engine to blow bluesmoke at startup? And also what does it mean that my purge valve isn't operating until 2800rpms? Is that gonna cause any sort of buildup of left over because of the fumes not being released until later?

Mazda2ndgen

do a search for it. I was looking to get rid of it just b/c and it was my impression that you could ditch it wihought a problem. i think you can remove the purgecontrol valve, put a litle crankcase filter in place of it so dirt wont get in, and cap off the 2 vacuum lines on the dynamic chamber

SpeedRacer

Cool...whats the best thing to use to cap of vacuum lines? Anything, or are there specific caps I can buy somewhere?

Keith

SpeedRacer,
The purge control valve opening is not RPM dependent, but throttle opening dependent. The vacuum line to the valve is opened when the throttle is a little ways off idle. With no load, I'm sure it gets to 2800 rpm, but under load it will be a lot sooner. Just nice to know info.

Irv, Keith's dad

HAILERS

Speedracer, finally a post I can answer. In a bind you can make a cap by cutting up a vacuum line and filling the end with that tube of rtv sitting on your work bench. Then again I've seen them at pep boys for a pittance. And also Speedracer, there's been post recently about the oil injectors being a possible cause of oil smoke and consumption. If you don't have anything to do you might check and see if they are functional. There. Exercised my fingers for the day. Have fun. Any one out there want to buy a intake manifold for a Holley that fits a sixport 13B. Cheap(relative). Digital code checker? Tps light checker?

rx74ever

hailers pm me about the light checker. just changed my o2 sensor and still crappy gas milage so i need to check my tps. thanks

Mazda2ndgen

you will need 2 1/8 inch vacuum caps. pep boys has them. i think they are like 1.99 for 5. just ask where the vacuum caps are, and get the 1/8inch ones