>what happens if you connect it back-ass-wards< Here's a little lesson in pneumatic engineering. (As they say, ask me what time it is and I'll tell you how to build a clock.) Three way valves exhaust through a port so as to vent the volume they're connected to. In this case the exhaust port is that loose cap on top of the solenoid. It has (or should have) a little filter inside it to keep dirt from being sucked into the valve and dizzy. To make matters more confusing it's a normally open solenoid (it *closes* when powered on at idle by the idle speed switch, thus shutting off vacuum to the dizzy.) That's backwards from "normal" solenoids which connect the in and out ports together when powered on. But where does the vacuum in the dizzy "go" after it's put in there? It can't stay there, it needs to equalize back to atmospheric pressure to remove the advanced timing. Hence the need for the "exhaust" port. (I know the ambient air is rushing *into* the dizzy in this case but it's still called an exhaust port, even when used in vacuum service) If plumbed correctly, when the valve is energized (idle switch closed) the exhaust port will be connected to the dizzy port so as to vent the closed volume of the advance unit. The intake manifold port will be isolated from the dizzy port. When the valve is de-engergized (off idle) the intake manifold port is connected to the dizzy port and the exhaust port is isolated (closed). This is how all three three way valves operate. It's a three way because it has three ports, two of which are always connected together when the solenoid is *de- energized*. This means you have to pay attention to which port the source (be it vacuum, compressed air or hydraulic)is connected to. If the valve was a simple two way which switched on and off with no exhaust port, there would be no way for the advance unit to equalize (vent to atmosphere) after it was evacuated by intake vacuum. ( If you plumb the hoses backwards two things will happen: 1)You'll have a direct intake leak when you're off at idle...you'll be sucking air through the exhaust port on the top of the valve because you've now got the vacuum source connected to the port thats pathed to the exhaust port when the solenoid is powered off. 2) The "vacuum" in the dizzy advance will be trapped and won't have a path to allow atmospheric pressure to vent it because you now have it connected to where the source should be and there is no path to *anywhere* when the solenoid is powered off, it's a closed volume. You'll end up staying advanced at idle until the advance volume leaks back up to atmospheric pressure, that could take a long time unless your diaphram is already torn or you have leaky connections. Confused? Think about it...or just be sure to plumb it per the vacuum schematic. And next time you have it off take a few minutes to play with it by powering it off and on and seeing which ports get connected to where. A complicated explanation for a simple concept eh? Now you know not only what will happen but also why...and thats far more important. Good thing there are no four ways in the car, I could really confuse you... Yahoo! Groups Sponsor ADVERTISEMENT <http://rd.yahoo.com/M=194081.3897168.5135684.1261774/D=egroupweb/S=170512 6215:HM/A=1732161/R=0/SIG=11p5b9ris/*http://www.ediets.com/start.cfm?code= 30509&media=atkins> click here <http://us.adserver.yahoo.com/l?M=194081.3897168.5135684.1261774/D=egroupm ail/S=:HM/A=1732161/rand=549110218> To unsubscribe from this group, send an email to: DMCForum-unsubscribe@xxxxxxxxxxxxxxx Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> .
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