Since there have been so many questions on the topic of CCV operation and failure, here is a description of how I think the CCV operates using Bluebee's picture for reference.
The vent pipe, swirl labyrinth chamber and vent hose are always at the same pressure or vacuum - there is no valve or obstruction between them. The swirl labyrinth is the lower part of the CCV assy that the vent pipe & vent hose connect to. Further, they connect to the valve cover & crankcase without restriction and are at crankcase pressure/vacuum.
The connecting line and return pipe connect to the inlet manifold which has a vacuum of ~20 inches Hg (mercury) at idle; ~260 inches water column vacuum.
The portion of the CCV immediately beside the blue "CCV" label in Bluebee's picture is a vacuum regulator whose job it is to maintain 4 -6" w.c. vacuum in the swirl chamber.
When the engine starts, the labyrinth is at 0 vacuum (i.e. vacuum is less than 4" w.c.) & the orifice/valve in the regulator is open. The gases in the swirl chamber flow through the regulator into the connecting line (which is at high vacuum), on to the inlet manifold and through the engine. Soon the vacuum in the swirl chamber (also the crankcase to which it is connected) is sucked down to 4 - 6" w.c. vacuum and the orifice valve in the regulator closes.
The engine runs, more blowby gases from the combustion chamber enter the crankcase & raise the pressure (reduce vacuum) in the vent pipe & swirl chamber. The regulator opens again, allows manifold vacuum in the connecting line to suck them away until crankcase vacuum is back to 4 - 6" w.c. at which point the regulator closes again. And on it goes, cycling over and over.
As the blowby gas travels through the engine toward the CCV, it picks up microscopic droplets/mist of oil. We don't want this oil mist to go through the vacuum regulator, into the inlet manifold and be burned: high oil consumption and air pollution. Enter the swirl labyrinth; it causes oil droplets/mist in the blowby gases to stick to the wall of the labyrinth and drain down the vent hose into the dipstick tube and sump while the "cleaned" gases carry on through the regulator.
6 Next, blowby getting past the piston rings enters the swirl chamber & moves up into the regulating valve chamber which reduces the vacuum.
7 With reduced vacuum, the spring is able to move the diaphram and open the vacuum port to the inlet manifold again
8 Vaccum inside the chamber is again sucked down - around & around it goes.,,,
As someone who is currently involved with a redesign of the CCV, and studied the system extensively, I can tell you that rdl is 100% correct in his description of how the system functions. In fact it is by far the best technical description I have seen to date.
I think we are all on the same page here. The diaphagm isolates the manifold vacuum (approx 260 inches of water) from the crankcase once the crankcase vacuum reaches 4-6 inches of water. The diaphagm modulates opening and closing the port to the intake manifold which regulates the crankcase vacuum to 4-6 inches of water.
It looks like both pictures that you uploaded are the same.
I'm still a little confused as to whether you agree with me and RDL on how the system functions, or if you are still taking an opposing view. I'm not trying to be sarcastic in any way, I'm just not sure if we are on the same page yet.
And this for the M54:Description of operation: fuel pressure regulator
Depending on requirements, the fuel pressure regulator regulates a low or high fuel pressure. This requirement is set with the help of the pressure regulator.
Depending on the engine's operating state, less or more fuel is needed:
- at idle speed, less fuel
- at full load, considerably more fuel.
The injection rate is precision-adjusted by means of the injection time; the injection time is controlled by the DME.
The partial vacuum in the intake manifold serves as engine load information for pressure regulation. The diaphragm of the pressure regulator is actuated with this partial vacuum.
A partial vacuum builds up in the intake manifold during idling operation or in overrun mode. Depending on the partial vacuum value, the fuel pressure decreases starting out from the nominal value. The nominal value is stamped in the fuel pressure regulator housing.
At full load, the partial vacuum in the intake manifold is approximately equal to zero. The fuel pressure regulator regulates the fuel pressure to the nominal value stamped in the housing.
Description of operation:
The control function of the fuel pressure regulator must be guaranteed under all operating conditions. The fuel pump must always be able to generate a higher fuel pressure than the pressure regulated by the pressure regulator.
The injection rate is adjusted by means of the injection time; the injection time is controlled by the DME.
Description of operation: fuel return line
When the engine is at a standstill and the ignition key is in position 0, the fuel return line after the pressure regulator is at zero pressure.
Description of operation: pressure retaining function
The pressure regulator closes when the engine is at a standstill and the ignition key is in position 0. The fuel pressure in the delivery line is retained over an extended period. A non-return valve closes in the fuel pump. These measures help to retain the fuel pressure in the fuel system. Extended starting times are thus avoided.