Jump to content

Vacuum Line Woes


Recommended Posts

Started piecing together the engine bay on the 79' Datsun I picked up a few weeks ago. I have got basically all the vacuum lines replaced and routed correctly but there are a few I am having trouble identifying what they are and where they go; any help would be very appreciated. 


As far as I can tell from the FSM the number 1 & 3 nipples are "manifold vacuum" and "vacuum switching valve for fuel cut & A.I.S. control switch" or " Carbon canister vacuum tube"


I do not believe it is for the carbon canister because the vacuum reference for that is tee'd into the same vacuum line as the vacuum advance.


As for number 2 it is either "Air inlet for A.B. valve" or "Air inlet for TCS"


Right now the A.B. valve is tee'd into the carbon canister vent going to the intake manifold which leaves TCS, but I am not sure what TCS is.





Link to comment
  • Replies 8
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

So I concluded that port 1 will be tee'd into a manifold vacuum line, and I think 3 can be plugged(Think it was used for a California emission option).


So that leaves port 2 which comes up right in front of the temperature control sensor(TCS). It seams like maybe it would be for a temperature signal from the manifold instead of the air cleaner?

Link to comment

Here's mine.



1 is pink and goes to that brass nut T which is on the egr block. 2 is green and plugs into the port at the little arrow, which comes out of that brass block with the screws which is mounted on the carb. 3 is blue and that goes to the carbon canister. Hope that helps.

Link to comment

BCDD valve, number 70,78 on this diagram, bottom left quadrant: http://www.carpartsmanual.com/datsun620/Datsun620Index/Engine(L20B)/Carburetor/tabid/2356/Default.aspx


in the picture I took, it's right where the little green arrow is, pointing more or less towards the camera which is right between the master cyl reservoirs.

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.