Choke Operation and Adjustment

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Categories: Hitachi 306 Carburetor | Fuel System | Engine Control

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Revision as of 03:25, 15 August 2009 ddgonzal (Talk | contribs) (->Choke Cable Part Numbers) <- Previous diff		Current revision ddgonzal (Talk | contribs) (->Wiring)
Line 1:		Line 1:
-	[http://datsun1200.com/modules/myalbum/photo.php?lid=7711 http://ddgonzal.members.winisp.net/getThumb.aspx?width=400&uri=http://datsun1200.com/modules/myalbum/photos/7711.jpg]	+	A gasoline engine only needs the choke (strangler) while warming up. When the engine is fully warmed, the choke must be fully off for correct operation.
		+
		+	{{Template:Hitachi_306}}
		+
		+	= Usage =
		+	== Manual Choke ==
		+	{{OwnersManualB120|06||STARTING THE ENGINE<br>
		+	<br>-- Engine Warm --
		+	<br>If the engine is relatively warm, you may not need to use the choke at all. Just press the accelerator pedal down about one-quarter of its travel to the floor, and thrn the ignition key in the switch to "START", when the engine starts running under its own power, release the key ...
		+	<br>
		+	<br>-- Enging Cold (Cold Weather) --
		+	<br>With a cold engine, pull the choke control button out all the way, press the accelerator pedal down slightly, and then start the engine. As soon as the engine starts, push the choke control button in far enough to keep the engine running smoothly ...
		+	<br>
		+	<br>-- Avoid --
		+	<br>Pumping the accelerator pedal before you start up does not do any good...}}
		+
		+	== Automatic Choke ==
		+	Automatic choke was first fitted to 1972 Datsun 1200 for North America market (Canada & USA). Fitted to Japan market Datsun 1200 for 1976.
		+
		+	Starting Procedure with Automatic Choke
		+	<br>{{Album|7711}} {{Album|21608}}
	= Operation =		= Operation =
Line 5:		Line 25:
	== Choked fully closed When Engine is Cold ==		== Choked fully closed When Engine is Cold ==
-
	Manual		Manual
	* With the dashboard Choke knob pulled all the way out, the choke butterfly on the carburetor should be fully closed.		* With the dashboard Choke knob pulled all the way out, the choke butterfly on the carburetor should be fully closed.
Line 13:		Line 32:
	Automatic		Automatic
	* With engine cold, moderate temperatures, the butterfly should close 100% (open throttle slightly to 'set' it)		* With engine cold, moderate temperatures, the butterfly should close 100% (open throttle slightly to 'set' it)
-
	== Choke fully open when Engine is Warmed Up ==		== Choke fully open when Engine is Warmed Up ==
Line 19:		Line 37:
	For an '''automatic choke''' (engine fully warmed up), the choke butterfly (looking down into the carb) should be fully open, as in the bottom part of this photo:		For an '''automatic choke''' (engine fully warmed up), the choke butterfly (looking down into the carb) should be fully open, as in the bottom part of this photo:
-	<br>[http://datsun1200.com/modules/myalbum/photo.php?lid=4401 http://ddgonzal.members.winisp.net/getThumb.aspx?width=220&uri=http://datsun1200.com/modules/myalbum/photos/4401.jpg]	+	<br>{{Album|4401}}
	<br>bottom: choke fully open		<br>bottom: choke fully open
	After warming up fully, if you manually close the choke butterfly, then the engine shouldn't idle correctly.		After warming up fully, if you manually close the choke butterfly, then the engine shouldn't idle correctly.
-	<li>It should idle nicely with the choke open</li>	+	<ul><li>It should idle nicely with the choke open</li>
-	<li>It it works fairly good partly closed, you have a vacuum leak somewhere</li>	+	<li>It it works fairly good partly closed, you have a vacuum leak somewhere</li></ul>
	== Choke Gradually Opens While Engine Warming Up ==		== Choke Gradually Opens While Engine Warming Up ==
-
	Manual Choke: Gradually push the knob in to open the choke butterfly. If you push it in too far, the engine may stall. If out too far, the engine "chugs" (runs rich). Experiment a little. Your goal is to make it run it's best. You will need to push the knob gradually in every 30 seconds or so until it runs well fully close (knob pushed to dash)		Manual Choke: Gradually push the knob in to open the choke butterfly. If you push it in too far, the engine may stall. If out too far, the engine "chugs" (runs rich). Experiment a little. Your goal is to make it run it's best. You will need to push the knob gradually in every 30 seconds or so until it runs well fully close (knob pushed to dash)
-
	Automatic choke: as soon as the engine starts vacuum should pull the choke open about 1/8 inch, by the [[Choke pull-off]] diaphragm. Otherwise, the engine "loads up" (runs rich) immediately after starting and might even die again.		Automatic choke: as soon as the engine starts vacuum should pull the choke open about 1/8 inch, by the [[Choke pull-off]] diaphragm. Otherwise, the engine "loads up" (runs rich) immediately after starting and might even die again.
		+	= Specifications =
		+	Original 1972 automatic choke
-	= Adjustment=	+	8.6 - 9.0 ohms @ 21C (70F) degrees temperature
-	== Automatic Choke ==	+	[measure with high-impedance gauge or [[wikipedia:Wheatstone bridge|Wheatstone bridge]]]
-	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 setting is on the middle mark:	+
-	[http://datsun1200.com/modules/myalbum/photo.php?lid=2212 http://ddgonzal.members.winisp.net/getThumb.aspx?width=400&uri=http://datsun1200.com/modules/myalbum/photos/2212.jpg] auto-choke adjustment	+	This implies the choke will draw about 1.2 amps maximum.
-	OK, here's the secret:	+	I = V/R
-	<ol>	+	Current = Voltage/Resistance
-	<li>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 if necessary.</li>	+	1.7 amps = 15 volts/9 ohms
-	<li>Then 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. It's just wired to the IGN (full +12V, before ballast resistor).</li>	+
-	<li>Note the single mark on the cover. Normally it is lined up in the center, and in the winter a mark or two tigher. Loosen the screws to turn this.</li>	+
-	</ol>	+
-	[http://datsun1200.com/modules/myalbum/photo.php?lid=7794 http://ddgonzal.members.winisp.net/getThumb.aspx?width=400&uri=http://datsun1200.com/modules/myalbum/photos/7794.jpg] Auto Choke Adjustment]	+	Note that Lead-acid battery voltage is regulated at about [[Voltage Regulator|15 volts]].
-	== Fast Idle Adjustment ==	+	== PTC Choke ==
-	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.	+	In 1975 the '''Positive Temperature Coefficient''' (P.T.C.) type Automatic choke type was introduced for North America engines.
-	[http://datsun1200.com/modules/myalbum/photo.php?lid=1007 http://ddgonzal.members.winisp.net/getThumb.aspx?width=400&uri=http://datsun1200.com/modules/myalbum/photos/1007.jpg]	+	<blockquote>A new positive temperature coefficient (P.T.C. heater) has replaced the previous coil heater.
-	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.	+	ELECTRIC AUTOMATIC CHOKE
		+	<br>... by changing the previous nichrome wire type into the P.T.C. heater. The temperature characteristic of the P.T.C. heater</blockquote>
-	[http://datsun1200.com/modules/myalbum/photo.php?lid=7792 http://ddgonzal.members.winisp.net/getThumb.aspx?width=400&uri=http://datsun1200.com/modules/myalbum/photos/7797.jpg]Fast Idle Adjustment & Dashpot	+	Basically it has a better opening curve to suit the engine without loading up in spots as did the early auto chokes. You can read more about choke technology in [http://www.google.com/patents/US3699937 Patent US 3699937]. Patent applied 1971. First application 1972.
-	* The [[Carburetor Dashpot]] is used on auto-choke models.	+	{{Album|24980}}
-		+
-	== Manual Choke ==	+
-	Manual choke adjustment procedure: There is no adjustment.	+
-	# To start when cold, pull the knob out.	+
-	# After starting, push the knob in a bit	+
-	# While warming up, constantly push the knob in or out until it runs right	+
-	# 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:	+
-	* Knob all the way out: ensure butterfly valve is fully closed	+
-	* Knob all the way in: ensure butterfly valve is fully open	+
		+	= Adjustment=
		+	See main article: [[Choke Adjustment]]
	= Wiring =		= Wiring =
-	Elecric Choke	+	1200 models starting with 1972 USA & 1976 Japan models were fitted with an automatic choke setup.
-	<br>[http://datsun1200.com/modules/myalbum/photo.php?lid=2211 http://ddgonzal.members.winisp.net/getThumb.aspx?width=400&uri=http://datsun1200.com/modules/myalbum/photos/2211.jpg]	+	<br>{{Album|2211}}
		+	<br>Choke harness wire = Red, seen at lower right of photo
-	* Red wire - To electric choke relay Y wire, and on through to the Alternator/Regulator "N" terminal. This supplies voltage only if the alternator is spinning, so that the choke doesn't heat up just from turning key to IG. The auto choke heater only heats up if the engine is actually running -- if it is turning the alternator.	+	This also uses a relay -- so wiring is complicated. However, you can simply connect the choke to 12V switch ignition (e.g. the ballast resistor). Using a relay that cuts power when the engine isn't running (alternator stops) is the preferred solution.
-	[http://datsun1200.com/modules/myalbum/photo.php?lid=14977 http://datsun1200.com/modules/myalbum/photos/14977.jpg]	+	{{Main|Electric Choke Wiring}}
-	The factory 1200 auto choke setup (1972 & 1973 USA models) uses a relay:	+	= Part Numbers =
-	* Red - to choke	+	RELAY - see [[Electric Choke Wiring#Part Numbers]]
-	* Yellow - to "N" wire of regulator/alternator	+
-	* Blue (L) - to Fuse 10A in fuse box IGN side	+
-	*: (also to Anti-diesel valve on 1973 carburetor)	+
-	* Black - to ground/earth	+
-	Location of Choke relay:	+	B110 USA
-	<br>[http://datsun1200.com/modules/myalbum/photo.php?lid=14979 http://datsun1200.com/modules/myalbum/photos/thumbs/14979.jpg]	+	14806-N2200 LABEL-AUTO CHOKE CONTROL
-	<br>To left of radiator	+
		+	Electric Choke can use Holley 5200 or Weber [[DGV]] choke [http://www.rockauto.com/catalog/x,carcode,1133480,parttype,6004 $10 to $15]
-	All this being said, you can simply hook the choke up to the Hot side of the ballast resistor -- it seems to work fine. The only downside I've observed is when you can't get the engine started right away, the choke heats up while you are trying. So using the alternator output and a relay is a better idea.	+	Also See: [[DCH Carburetor Part Numbers]]
		+	1974 A13 choke thermostat cover (fits 1200)
		+	<br>{{Thumb|26526}} {{Thumb|26527}} {{Thumb|26528}}
-	= Choke Cable Part Numbers =	+	= Also See =
-	See main article: [[Choke Cable]	+	[[Choke Cable]]
		+	[[Carburetor Parts]]
		+	[[Choke Linkage]]
	[[Category:Fuel System]]		[[Category:Fuel System]]
		+	[[Category:Engine Control]]{{End}}

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Current revision

A gasoline engine only needs the choke (strangler) while warming up. When the engine is fully warmed, the choke must be fully off for correct operation.

Contents 1 Usage 1.1 Manual Choke 1.2 Automatic Choke 2 Operation 2.1 Choked fully closed When Engine is Cold 2.2 Choke fully open when Engine is Warmed Up 2.3 Choke Gradually Opens While Engine Warming Up 3 Specifications 3.1 PTC Choke 4 Adjustment 5 Wiring 6 Part Numbers 7 Also See

Usage

Manual Choke

Automatic Choke

Automatic choke was first fitted to 1972 Datsun 1200 for North America market (Canada & USA). Fitted to Japan market Datsun 1200 for 1976.

Starting Procedure with Automatic Choke
Album 7711 Album 21608

Operation

Here is what to expect from a choke:

Choked fully closed When Engine is Cold

Manual

• With the dashboard Choke knob pulled all the way out, the choke butterfly on the carburetor should be fully closed.
• In normal operation, only when the engine is cold should the choke be partially closed (knob pulled out)

Automatic

• With engine cold, moderate temperatures, the butterfly should close 100% (open throttle slightly to 'set' it)

Choke fully open when Engine is Warmed Up

For a manual choke (cold or hot engine), with the dashboard knob pushed all the way in, the choke butterfly should be fully open

For an automatic choke (engine fully warmed up), the choke butterfly (looking down into the carb) should be fully open, as in the bottom part of this photo:
Album 4401
bottom: choke fully open

After warming up fully, if you manually close the choke butterfly, then the engine shouldn't idle correctly.

• It should idle nicely with the choke open
• It it works fairly good partly closed, you have a vacuum leak somewhere

Choke Gradually Opens While Engine Warming Up

Manual Choke: Gradually push the knob in to open the choke butterfly. If you push it in too far, the engine may stall. If out too far, the engine "chugs" (runs rich). Experiment a little. Your goal is to make it run it's best. You will need to push the knob gradually in every 30 seconds or so until it runs well fully close (knob pushed to dash)

Automatic choke: as soon as the engine starts vacuum should pull the choke open about 1/8 inch, by the Choke pull-off diaphragm. Otherwise, the engine "loads up" (runs rich) immediately after starting and might even die again.

Specifications

Original 1972 automatic choke

8.6 - 9.0 ohms @ 21C (70F) degrees temperature
[measure with high-impedance gauge or Wheatstone bridge]

This implies the choke will draw about 1.2 amps maximum.

I = V/R
Current = Voltage/Resistance
1.7 amps = 15 volts/9 ohms

Note that Lead-acid battery voltage is regulated at about 15 volts.

PTC Choke

In 1975 the Positive Temperature Coefficient (P.T.C.) type Automatic choke type was introduced for North America engines.

A new positive temperature coefficient (P.T.C. heater) has replaced the previous coil heater. ELECTRIC AUTOMATIC CHOKE
... by changing the previous nichrome wire type into the P.T.C. heater. The temperature characteristic of the P.T.C. heater

Basically it has a better opening curve to suit the engine without loading up in spots as did the early auto chokes. You can read more about choke technology in Patent US 3699937. Patent applied 1971. First application 1972.

Album 24980

Adjustment

See main article: Choke Adjustment

Wiring

1200 models starting with 1972 USA & 1976 Japan models were fitted with an automatic choke setup.
Album 2211
Choke harness wire = Red, seen at lower right of photo

This also uses a relay -- so wiring is complicated. However, you can simply connect the choke to 12V switch ignition (e.g. the ballast resistor). Using a relay that cuts power when the engine isn't running (alternator stops) is the preferred solution.

Part Numbers

RELAY - see Electric Choke Wiring#Part Numbers

B110 USA 
14806-N2200 LABEL-AUTO CHOKE CONTROL

Electric Choke can use Holley 5200 or Weber DGV choke $10 to $15

Also See: DCH Carburetor Part Numbers

1974 A13 choke thermostat cover (fits 1200)
Album click to view Album click to view Album click to view

Also See

Choke Cable
Carburetor Parts
Choke Linkage 

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