Hi,
I've noticed there's only ONE vacuum diagram on the DIY section and it's not for my car but rather seems it's for the 380SEC. Then i've noticed other diagrams but they're for later versions of my car or US versions. So, after two weeks for reading the manual, here are the ENGINE VACUUM DIAGRAMS / LAYOUT / CIRCUIT for a 1982 Euro 500 SEC (C126), with explanation from yours truly.
Feel free to correct me because i know i will make some mistakes here.
First to know, for engine there are at least SEVEN vacuum connections, two on the top of the intake manifold and five on the throttle valve housing. Let's start with this diagram, Pressure Regulator Vacuum.
The pressure regulator (also known as warm up regulator regulates the control pressure that goes to the fuel distributor. More control pressure= LESS fuel to the engine. Less control pressure= more fuel to the engine.
The fuel regulator has an upper diaphragm (main diaphragm). When it goes UP, the control pressure goes UP so the mix has less fuel. When it goes DOWN, the control pressure goes DOWN so the mix has more fuel. The fuel regulator also has an thermoelectric element that will pull the diaphragm DOWN (more fuel) until heated. This is for increasing the mix when the engine is cold.
Then, the regulator also has two vacuum connections at the side, g (upper) and h (lower). This is for the lower diaphragm, located at the bottom of the regulator, which is moved by vacuum on g and h, and also influences the control pressure regulating diaphragm.
When vacuum(g)>=vacuum(h), the vacuum diaphragm on the regulator goes UP. This is the steady, normal operating state of the engine. (Thermoelectric element hot and vacuum diaphragm up==normal engine operation).
When vacuum(g)<vacuum(h); this will pull the control pressure regulating diaphragm DOWN thus increasing the mixture.
Now look at the diagram. Thermovalve 37A opens at temperatures more than 50 deg celsius. Opens==lets the vacuum pass.
Throttle housing "switchover valve" (13) normally connects C with D, unless you open the throttle all the way down; in that case, it only connects C with E.
Vacuum reservoir (14) holds up vacuum. This item perhaps is located on/under the driver's front fender. I haven't found mine yet.
Orifice (9) is just that, an orifice to change the vacuum respect to other connections.
Warm-up acceleration enrichment
So, back to the diagram. When the engine is <50ºC, thermovalve 37A is closed. Assuming throttle is not wide open, switchover valve 13 will connect C with D. On acceleration, vacuum(g)<vacuum(h) and thus the fuel mixture will be richer.
When the engine is >50ºC, thermovalve 37A effectively connects vacuum(g) with vacuum(h), so this acceleration enrichment will be cancelled.
Full throttle acceleration enrichment (temperature independent)
When throttle is wide open, C will be connected with E. This means the vacuum reservoir (13) will suck through vacuum hose H. So vacuum(g)<vacuum(h)==> FUEL ENRICHMENT!
Other connections
Connection F goes straight to the distributor for vacuum distributor timing advancement.
Connection K should go to the intake manifold for sucking the vacuum reservoir, but i still don't know where K goes.
Connection I (top of pressure regulator) should go to the "atmosphere" (and it makes sense after looking at the internals of that part) but in my car this is connected to the top of the idle speed adjusting solenoid. I assume it's almost atmosphere there. [Update: Yes, that's the right location for that connection]
I've noticed there's only ONE vacuum diagram on the DIY section and it's not for my car but rather seems it's for the 380SEC. Then i've noticed other diagrams but they're for later versions of my car or US versions. So, after two weeks for reading the manual, here are the ENGINE VACUUM DIAGRAMS / LAYOUT / CIRCUIT for a 1982 Euro 500 SEC (C126), with explanation from yours truly.
Feel free to correct me because i know i will make some mistakes here.
First to know, for engine there are at least SEVEN vacuum connections, two on the top of the intake manifold and five on the throttle valve housing. Let's start with this diagram, Pressure Regulator Vacuum.
The pressure regulator (also known as warm up regulator regulates the control pressure that goes to the fuel distributor. More control pressure= LESS fuel to the engine. Less control pressure= more fuel to the engine.
The fuel regulator has an upper diaphragm (main diaphragm). When it goes UP, the control pressure goes UP so the mix has less fuel. When it goes DOWN, the control pressure goes DOWN so the mix has more fuel. The fuel regulator also has an thermoelectric element that will pull the diaphragm DOWN (more fuel) until heated. This is for increasing the mix when the engine is cold.
Then, the regulator also has two vacuum connections at the side, g (upper) and h (lower). This is for the lower diaphragm, located at the bottom of the regulator, which is moved by vacuum on g and h, and also influences the control pressure regulating diaphragm.
When vacuum(g)>=vacuum(h), the vacuum diaphragm on the regulator goes UP. This is the steady, normal operating state of the engine. (Thermoelectric element hot and vacuum diaphragm up==normal engine operation).
When vacuum(g)<vacuum(h); this will pull the control pressure regulating diaphragm DOWN thus increasing the mixture.
Now look at the diagram. Thermovalve 37A opens at temperatures more than 50 deg celsius. Opens==lets the vacuum pass.
Throttle housing "switchover valve" (13) normally connects C with D, unless you open the throttle all the way down; in that case, it only connects C with E.
Vacuum reservoir (14) holds up vacuum. This item perhaps is located on/under the driver's front fender. I haven't found mine yet.
Orifice (9) is just that, an orifice to change the vacuum respect to other connections.
Warm-up acceleration enrichment
So, back to the diagram. When the engine is <50ºC, thermovalve 37A is closed. Assuming throttle is not wide open, switchover valve 13 will connect C with D. On acceleration, vacuum(g)<vacuum(h) and thus the fuel mixture will be richer.
When the engine is >50ºC, thermovalve 37A effectively connects vacuum(g) with vacuum(h), so this acceleration enrichment will be cancelled.
Full throttle acceleration enrichment (temperature independent)
When throttle is wide open, C will be connected with E. This means the vacuum reservoir (13) will suck through vacuum hose H. So vacuum(g)<vacuum(h)==> FUEL ENRICHMENT!
Other connections
Connection F goes straight to the distributor for vacuum distributor timing advancement.
Connection K should go to the intake manifold for sucking the vacuum reservoir, but i still don't know where K goes.
Connection I (top of pressure regulator) should go to the "atmosphere" (and it makes sense after looking at the internals of that part) but in my car this is connected to the top of the idle speed adjusting solenoid. I assume it's almost atmosphere there. [Update: Yes, that's the right location for that connection]
