Choke on 240Z - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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#1 (permalink) Old 12-09-2006, 10:15 PM
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Choke on 240Z

I just picked up my 71 240Z, I don't know much about the Choke system and how to work them right. I am in the DC area and it is really cold here. I was told to open the choke to start in the cold. Once I open the choke and start the car, should the choke remain open all the way or....... what happens if I start the car with the choke open (in the cold) and colse it a few minutes later..... I am at a lost here

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#2 (permalink) Old 12-09-2006, 11:00 PM
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Re: Choke on 240Z

What i try to do in the colder a.m. weather is 3/4 to full choke on,then slowly bleed the choke off,as the engine becomes warmer,eventually bleeding off in about 5-7 minutes ( a little warmer out here!)just make sure your idle isin't excessive.

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#3 (permalink) Old 12-09-2006, 11:08 PM
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Re: Choke on 240Z

The choke lever on the 240Z aids in starting your car in cold weather when there isn't sufficient heat to vaporize fuel in the carburettors. After 30 some odd years every 240Z will be different. I used to choke the carbs to start up and warm the engine enough that it'll idle on its own. After its warmed up I'd redline it once driving down the street to "burn off" excess fuel. It'll run perfectly after that.

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#4 (permalink) Old 12-10-2006, 06:37 AM
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Re: Choke on 240Z

Note he said red line it when it was warm, never rev a car excessively when you just start it up from cold.

1973 240Z Turbo (L28ET) - Engine currently on stand and in bits, car currently on axle stands and in bits too!
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#5 (permalink) Old 12-10-2006, 06:56 AM
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Re: Choke on 240Z

On the Z, you want to pull back on the choke away from the dashboard to cloose them about about 3/4 of the way to start the motor. After it's started, you can let off the choke a bit by pushing it foreward toward the dashboard. Listen to the motor while you are doing so, you'll hear the tone of the motor change. As you are driving the Z before it is fully warmed up, you'll have to make minor adjustments to the choke, pushing and pulling it until it fully warms up. Once it's finally warm, push the choke foreward completely to open them up.

It takes practice to learn your car, but when you finally have a feel for it. You won't think twice about it.

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#6 (permalink) Old 12-11-2006, 01:05 AM
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Re: Choke on 240Z

If you are the kind that doesn't like to wait around after starting, then Nomad Z has the best advice. I used to do that in the winter (Lake Tahoe), now I start it and wait for it to warm up completely. There is nowhere I have to be so badly that I can't wait for it to warm up.

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#7 (permalink) Old 12-11-2006, 01:38 PM
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Re: Choke on 240Z

Two things to take into account. One is to use the winter/summer lever on the air filter housing. It blocks off direct cold air and pulls warm air through a metallic hose from the exhaust manifold area to aid in fuel vaporization. Secondly, the 'choke" on a SU provides additional fuel fuel by lowering the nozzle allowing more fuel past the needle. While more fuel is supplied at all rpms with the nozzle lowered it won't much as much difference off idle as many suspect. Also, for a daily driver in cold weather it is worthwhile to have the coolant circulate through intake manifold (factory setup) to aid in fuel vaporization. My 71 has this blocked off and is a cold natured beast until it fully warms up. I use the choke only to start and idle. I take the choke off as I run down the road then reapply when approaching a stop to prevent the engine from dying.

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#8 (permalink) Old 12-11-2006, 08:20 PM
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Re: Choke on 240Z

Check the console for cracked off choke lever bracket mounting pylons. They are virtually guaranteed to be broken off. Save the plastic, drill all the way thru the console and install longer, decorative screws (ie countersink Phillips head with escutcheon washers) to properly secure the choke lever bracket.

Check the push-pull setup on the console lever. Make sure it is tight and lubricated, grasping the wire cable tightly, yet free to pivot on the shoulder screw.

Unhook the choke cables from the carbs, and point them straight up. Clamp on 6" pieces of 1/4 fuel hose and fill with oil to syphon feed the cables liberal amounts of oil.

While the cables are soaking, work the carb choke levers by hand. Upon pulling each lever, the corresponding fuel nozzle should drop about 1/4 inch, and return freely upon release of the lever. These carbs are notorious for stuck/sticky fuel nozzles. If stuck, or sluggish: remove the nozzle from the carb by unscrewing the actuating lever and unhooking the fuel hose (don't drop any of the small parts!) Clean the nozzle and apply moly grease, copper-based grease, or graphite-based grease. Reassemble. Remove domes and set nozzle depth at .100 (2 1/2 turns). When the nozzles are working smoothly, watch the throttle butterfly for each carb when working the choke lever. Bend the adjusting rod so that as the nozzle begins to move, the butterfly moves at the same time (for correct fast idle).

If correctly set up, these are some of the best-starting carbs around. Use the choke lever to modulate fast idle/choke while warming up/driving. When the engine is warm enough, of course the choke will no longer be needed.
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