Hi everyone,
 
I'm in the process of fitting up the charcoal canister, and after studying both the Gregory's and Ford manuals, it seems I either never had a vacuum switching valve fitted (meaning my canister didn't function correctly), or I simply don't know what it looks like. Would someone kindly post a picture of one? I want to use the canister because fuel vapours are worth burning rather than spewing into the atmosphere unburnt.
 
Thanks.

Hi Flighter,
 
Which model vehicle? 

Silly me - '78 Escort 2.0.

Hi Flighter,
 
I don't recall there being a vacuum switching valve.
The idea was the carbon in the carbon canister would absorb (store) fuel vapour which would be drawn into the carburetor during engine operation.
Highly unlikely the carbon is still active nearly 40 years later. 
 
I will check my cars tomorrow and confirm.
 
 

Are you talking about the valve on the inlet manifold near the carb on auto models? I can take a pic of mine if you want? I doubt you'll find one.

Hi Flighter,
 
I checked both of my cars today:
 
Escort 1.6 litre panel van July 1979 build, completely factory standard car:
There are 3 hoses from the carbon canister (from the fuel tank, to the carby, from the air filter casing.)
There is no vacuum switching valve just straight hoses.
 
Escort RS2000 very late December 1979 build concourse resto, mechanically correct, date correct:
There are 2 hoses from the carbon canister (from the fuel tank, to the carby.)
There is no vacuum switching valve just straight hoses.

Peter,
The vac switching valve is only found on the auto models. It operates the egr valve. Mine is electronic. If you look in the Gregory's manual 125 page 211,there is a diagram and if you look at the pic on 213 you can see the wires that run up to it.

I'll grab a pic tomorrow in the daylight.

Flighter,

In short, you dont need it.
If you don't already have it, you wont find it.

Shaun.

Thanks for all the replies. I might fit a 'vacuum check valve' I found on an old Pinto I have sitting around, as per this video:
https://www.youtube.com/watch?v=uMGMOOjNvPY
 

Sorry, forgot to add the photo,
 
Just for interest,
 
Here is the switch with hoses removed for clarity.
 
There is also a switch on the throttle to the rear of the carby.
 

 
 

That vacuum switch and the carby throttle actuator, are a part of a/c idle up system.
When vacuum switch is energised it allows vacuum to reach the actuator which slightly opens the throttle (its adjustable) to raise idle speed to compensate for extra load of the a/c compressor and to less extent extra electrical load from a/c clutch, condenser fan and evaporator fan.