Vacuum Hose Routing

(Difference between revisions)

Revision as of 03:25, 8 May 2014

Vacuum hoses on the 1200 follow a simple layout.

Overview

1. VACUUM ADVANCE
2. CHOKE PULL-OFF

Vacuum Advance

The A12 will run good with the vacuum advance disconnected, but will run smoother and get better fuel economy with it working.

Connect a hose from the distributor to the port connection directly above the idle mixture screw.

Vacuum advance in all models uses a hose from the 'port' on the carburetor to the Distributor.

VACUUM ADVANCE. You want this as more advance = more power. This is a good system that adds extra performance, better fuel economy, and smoothness to the driving experience. And because vacuum is zero at full throttle, it has no effect on full throttle performance.

Just check to make sure it holds vacuum. Most are leaking. If yours is leaking, just plug the hose. It'll run better plugged than leaking. But you won't get good fuel economy, so best to replace it. Sometimes you can find them at wrecking yards still working. Or buy a new one for $75. Units from many other Datsuns fit, and some Honda and Subaru.

You can also test it without a vacuum gun. Move it with screwdrive and check to see if will hold under your thumb.

For more information, see Vacuum Advance

Carbon Canister

For late model 1200s, Tee into this line and connect a hose to the Charcoal Canister "VC" line. The canister is for the Fuel Tank vent. Since these fuel tanks are sealed, it needs to vent somewhere.

just three connections:
1. Fuel tank vent line (connection by itself)
2. PURGE - to intake manifold (bottom connector)
3. Vacuum Control (top connector) - to vacuum advance hose

Choke Pull-off

For Datsun 1200s with Automatic Choke

Choke Pull-off port, hose & diaphragm. Nissan calls this the "Vacuum Break"

This long black hose goes to the choke pull-off diaphragm (vacuum motor):

Test this diaphragm the same way as the vacuum advance.

Hopefully it won't be leaking. Again, better to plug this than have it leaking. You can drive the car with this plugged, but after a cold start it will run very rich for some time until the choke warms up a bit. It may even want to die unless you have your foot on the pedal a bit.

Only about $15 for a new one if you compare prices.

See Choke pull-off

USA

USA models have more emission controls, so a couple extra lines are used.

See:

• Emission Controls#Throttle Opener
• Emission Controls#Temperature Controlled Air Cleaner
• Fume Control (for the Flow Guide Valve details)
• TCVAS