1974 L18 620 Engine Vacuum Line Schematic: Need or Where to find

[Cardinal Grammeter]

I think I may have screwed something up.

 

BCDD I remember from long ago, that simply pushing the adjust screw in with the screwdriver also worked the diaphragm and you could hear the unit hissing and working.

 

Now it does nothing when screw pushed in or is adjusted either way.  Solenoid is working and there is 12v present.  NOTE:  from what I remember, simply revving the engine and noting the amount of "rpm hang" was the way to tune.

 

Also need to know what the vacuum line on the BCDD does - I guess either it goes to manifold vacuum OR clean air from air cleaner - I guess that is the question for every line....  except for the inner fender "multi valve" coming off the fuel tank vent (probably has to be clean air from air cleaner since vacuum should make NO sense.)  

 

Does the 74 L18 have a canister up by the radiator or somewhere?

 

Carb is also behaving like there is no power valve enrichment in the primary.  I swear I put the carb manifold gasket on the right way.

[datzenmike]

Hose is intake vacuum. Turn screw counter clockwise to reduce the BCDD's sensitivity of turning on.

[Cardinal Grammeter]

I just found my 8 year old thread addressing this:

 

The FSM shows:  The B.C.D.D. has a nipple that needs clean air from the air cleaner.  (EF-22 Sectional View of BCDD)

NOTE:  This might explain other carbs with the BCDD that have no nipple.

 

OK so it's manifold vacuum to BCDD.  However the darn thing is dead.  Adjusting screw does nothing - nor does disconnecting the solenoid power lead.

 

And there is no idle hang whatsoever.  BUT when going down hill in gear, there is what I'd call excessive "rumble, "racking off", back firing out the tailpipe (could really hear it with the leaky exhaust pipe slip joint.)  Don't know if the BCDD would affect that.

 

I have to laugh, it behaves like it isn't there which is what some people want!

 

ALSO, that hot idle compensator in the air cleaner, I believe that is simply a "vacuum leak" thermal valve so that plumbs to manifold vacuum.

Edited March 11, 2022 by Cardinal Grammeter