Vacuum Hose Routing

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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

EGR

EGR is used by 1989-up Japan 1200s & 1975-up USA B210 & B310 models

3rd connector on carburetor is for EGR. If the EGR system is missing from your engine, then on carburetor plug the port connection that is slightly above the Vacuum advance port (and above the idle mixture screw on the rocker cover side of the carb).

For testing, you can drive the car under all conditions with the EGR port plugged. Performance should be equal or better with it plugged.

Throttle Opener

Throttle Opener diaphragm which is attached to the carburetor. Was used most USA B110 from 1972 and B210s except the FU engines (5-speed models).

For getting an engine first running, or for testing, remove the hose at the intake manifold and plug it. The engine will run good this way.

orange hoses in the diagram above: a single vacuum hose from the intake manifold to the switch. Then another from the switch to the Throttle Opener. In the diagram it shows a 3rd hose on the switch, which goes to the bottom of the air filter. That's all the hoses it uses. The rest is electrics.

If operating correctly, the throttle opener does not interfere with driving, although it does hold the throttle open a little during shifting. If misadjusted, it will be intrusive, holding the throttle open too far or for far too long.

Quick Test: Remove the hose at the intake manifold and plug it. See if the engine runs better. The car will drive OK with this plugged -- I think. Let us know how it works.

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