Choke Adjustment

(Difference between revisions)

Revision as of 00:13, 20 October 2012

When the engine is fully warmed, the choke must be fully off for correct operation. When the engine is cold, the choke should be partly for fully closed. When the outside temperature is cold and engine is cold it must be fully closed. See Choke Operation for more details.

Automatic Choke

To adjust the automatic choke, slightly loosen the three screws holding the round part. Rotate it counterclockwise for more choke, clockwise for less.

The nominal (initial) choke setting is on the middle mark:

NOTE: This 'nominal' setting is where a carburetor rebuilder will set it. BUT IT IS NOT THE FINAL SETTING.

Here's the secret to easy and correct adjustment:

1. Set it (engine fully cold) just tight enough to just close the choke completely when tthe throttle is opened. Since it depends on outside temperature, adjust summer and winter as necessary.
2. Warm the engine up. Blip the throttle occasionally to let the choke open as the spring warms. If, when the engine is fully warm, the choke hasn't completely opened, there is a problem. Check the spring on the choke. If it don't have enough 'spring', by a new electric one.
3. Note the single mark on the cover. Initally it is lined up in the center, then final adjusted per Step 1. In the winter set it a mark or two tighter (following step 1). Loosen the screws to turn this.

Hitachi chokes can be silver or black. They both work the same, are same diameter, and are wired the same. One or two wire units are connected the same. Note the Hitachi symbols.

Center mark - WRONG (choke is not closed with carb/engine cold). Center mark is just an intial setting.

Correct for this carburetor for winter. Note that choke has fully closed with housing rotated this far. It will vary by carb and choke heater -- and whether summer or winter

While checking the rotation, push the butterfly down and let it spring back. You want it where it will just fully close each time. If you turn it farther it may not open fully when warm.

ALSO IMPORTANT: Open the throttle a bit and check that the choke butterfly still closes all the way.

Tighten the choke housing screws (lightly, they are just tiny screws!), the warm the engine fully up, then ensure that the choke has opened 100%. Blip the throttle. If the choke is not 100% open (straight up and down) then the heater is not working correctly (may not be getting voltage, or may be worn out).

Rebuild initial setting

Fast Idle Adjustment

This should only have an effect when the engine is cold, as it is related to the choke. The engine should run fast when started, then as it warms up and the choke is gradually released (blip the throttle to 'set' the cam), it should run slower until as the engine warms more, it comes off the cam and has no effect on warm engine.

Fast Idle Adjustment

Adjust for about 1200-2000 rpm (cold) or to your preference. It should be fast enough to run good, but not too fast. While Nissan has a specification, really it depends a lot on how cold it is where you live. If everything else is adjusted correctly (timing, no vacuum leaks, etc), you should be able to take off immediately and drive the car without "warming it up". If it dies, use a higher fast idle.

Fast Idle Adjustment

Manual Choke

Manual choke adjustment procedure: There is no adjustment.

1. To start when cold, pull the knob out.
2. After starting, push the knob in a bit
3. While warming up, constantly push the knob in or out until it runs right
4. When fully warm, the knob should be all the way to the dash

The only thing to check regarding choke, mechanically speaking is: remove air cleaner and inspect:

• Choke knob all the way out: ensure butterfly valve is fully closed
• Choke knob all the way in: ensure butterfly valve is fully open

If this is not working correctly, loosen the choke cable clamp at the carburetor, adjust position of cable and tighten the clamp.