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Idle Box, how to set


610StaWag

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Lost the idle again. The idle solenoid is still connected and it does click on when key is turned on. Recently when I was cleaning things in the engine bay area I noticed this box between the engine and firewall with a cover so cloudy I couldn't tell what it was. I decided to take the cover off to polish out some of the cloudiness. Clumsy me, I unscrewed the unit not knowing that the cover popped off. I thought I put every thing back in place but now that the engine doesn't idle again I wounder if I messed something up. What should I do?

 

29238813723_1b7a28925f_b.jpgIdle Box by Donald Broz, on Flickr

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Not really anything to do with idle. It's for the emissions. It tells the emissions system when the gas pedal is not being used or is in the closed position. In conjunction with a transmission switch it allows or denies the second (retard set) of points to be used.

 

Try closing the switch. If it doesn't change anything then it's not the cause.

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Engine starts and runs great, no dirt in filter. Idle solenoid connection works fine. Carb is not loose.

 

Re: "Try closing the switch." How is that done? Should I just experiment by loosening the screw (red arrow) and move the plate to different positions (eg., moving blue and green closer or further apart)?

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 29238813723_1b7a28925f_b.jpg

 

You know, I may have to change what I said earlier. I thought that was the same switch as used on the 510 dual points set up.I think this is a fuel shut off. Here's how it works. Above idle the fuel going to the idle circuit isn't needed so the switch is in line with the idle cut solenoid. It opens and the idle cut goes off and closes fuel to the idle. It isn't needed and just goes to waste anyway. When stopping and foot is off the gas the idle cut is turned on so it will idle.

 

Later 79 620s and all 720s have a vacuum switch which turns the idle cut off only during high vacuum deceleration IF the clutch is not down and the transmission is not in neutral.

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The lack of idle plot thickens...I got in the car, pumped the gas pedal twice, turned the key and engine started immediately, had plenty of power/ran great,.. but no idle. I was backing out and I ran over something  big enough so that the car bounced...then lo and behold the engine idled! I gave it some gas and took my foot off the pedal and, yes, the engine was idling. I turned the engine off, checked what rock I ran over with my right front tire. It was only the right front tire. I couldn't see anything wrong so I moved the car back into the carport and ... no idle.  What do you think happened? 

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Thanks guys.

 

I'll try that blue choke heater wire Mike.

 

Ahh, Mr. Racerx, just where is that ballast resistor you mentioned and what does this one look like?

 

Parts stores  I have called do not have a listing for a Datsun "Idle solenoid", is there a specific technical name for it? Can it click and still not function correctly?

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The car starts and runs great.

 

Now a real interesting thing...This morning, before I tried the blue wire thing...I went out to the car, raised the hood, took off the air cleaner and was about to do the blue wire jump when I noticed the choke was not completely closed (see photo). I  took my finger and with a little pushed the choke closed completely (see photo). I opened the door and I then put the key in the switch. I wanted to just turn the switch to try to hear the solenoid click. But I turned it too far, and in a split second (I didn't even have my foot on the gas pedal) the engine stsrted and went right to a perfect idle! I called my wife (it really is her car), and we both stood by the car marveling at the perfect idle. We let the car idle for awhile. Then I got in the car, shifted into reverse, went back about a foot,  stopped, put the clutch in, took my foot off the gas and there was no idle. I shifted into neutral, and restarted the car. Engine started perfectly, but no idle.

 

The engine was warmed up I guess, when I looked at the carb the choke was open. I manually closed it with my finger. I turned the key (no foot on the gas pedal) and the engine started and had a VERY fast idle. I stepped on the gas (the choke had opened) and when I took my foot off there was no idle.

 

At first I wondered if there was a bad switch on the trans or somewhere else. Then I wondered, is this just a case where I have to adjust and idle set-screw???

 

I tried the blue wire from the choke but no difference.

 

What/how do I check a ballast resistor...ohms? break in circuit?

 

(I did try rotating the Idle Box, but nothing seemed to happen)

 

29734999740_23a3427abc_b.jpgCarb-Choke-adjust screws by Donald Broz, on Flickr

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if you have  ballast resisitor you car wont run.  above idle or not.

 

ballast resisitor

look near the coil. there will be wires going into a 2.5 inch ceramic or metal retantangle  block with wire goin to and from also goes to coil.  You can put a test light on one side or another if its broke it wont light up.  Key ON.

 

 

I get canned air and remove the idle curcut jet, or selinoid and blow thru it.  So just to let you know I do this in weber DGVs and don't have a selinoid , so your at your oown risk. in case of loosing something.. I drop my jet in the gravel and couldn't find it but had a stash of spares.

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29734999740_23a3427abc_b.jpg


If you start with a cold engine that wassitting over night and you look at the choke, it will look like the picture on the right.

 

If you step on the gas pedal the chock should snap closed like the picture on the left. On a cold or partly warm engine you have to depress the gas pedal to set the choke. It won't start without this. Check and see if this is the case. If not this is a problem that needs correcting.

 

Start engine.

 

When warmed for 10 min have a look at the choke, it should be fully open with the flap vertical. If not this is a problem that needs correcting.

 

 

 

 

 

Now as to running a perfect idle.... remember that the choke is ON and the choke will make the engine run much richer. If you have a problem with the idle when engine is warm, this is masked by the choke being on when it's cold. Do not adjust the idle mixture when the choke is on, remember that the choke is forcing a rich mixture that will disappear once the engine warms and the choke is off.

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Yes, in the morning it looked like the photo on the right. I tapped the choke and it closed like that on the left. At this point I turned the key and the engine started perfectly & had a normal speed idle without me putting my foot on the gas pedal. What a wonderful 43 year old engine that has never had a need for any engine work!

 

If you start with a cold engine that was sitting over night and you look at the choke, it will look like the picture on the right.

If you step on the gas pedal the chock should snap closed like the picture on the left. YES

 

"If you have a problem with the idle when engine is warm, this is masked by the choke being on when it's cold." Yes, this seems to be the case. When the engine is warm, and the choke is open, there is no idle.

 

Am I at the point where I should just adjust the idle screw? Is it the yellow or red one? Which way should I turn it, and how much should I turn it to begin with?

Is there a need to the idle mixture? Is it the yellow or red one? Which way should I turn it, and how much should I turn it to begin with?

 

Thank you!

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im going to take a stab at this, the yellow one looks like the air/fuel screw and red looks like idle screw. red one looks like its hooked to throttle. maybe similar to weber 32/36. turn red one, clock wise, listen to idle, if it goes up then thats how u adjust the idle. but prior to messing w idle make sure ur timing is good. also make sure u dont have a vacuum leak, adjustment will be difficult.

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When the choke is engaged there is a fast idle function as well. A richer mixture needs more air. The fast idle can even rev as high as 2K to speed the warm up.

 

 

If adjusting the idle it has to be done on  a warm engine.

 

The idle cut solenoid must be working. You should hear a light click sound when the ignition is turned on and off.

 

 

To set the idle speed and mixture on a vehicle that is not idling, turn the Red idle speed screw in until you do have an idle. Set as low a speed as possible. Now turn the Yellow mixture screw in or out. If idle quality drops turn the other way. Always move towards an improved idle and idle speed. Turn the Red idle speed down as low as possible and repeat by turning the Yellow mixture screw in or out slowly to find the smoothest fastest idle. Turn Red speed screw to lower the idle and repeat the process as many times as needed until you cannot improve on the idle quality and the idle speed is 750-850.

 

If you cannot get the idle below 1,200 without stalling then the idle cut may not be shutting off. You can unscrew the idle cut solenoid and remove the steel needle inside and replace it. This should give you back your lower idle speed. Now continue setting the idle mixture and speed.

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I need to apologize to all of Ratsun that has tried to help me with my problem of my Datsun 610 with no idle. I am more than embarrassed that I did not pay attention to such a simple thing as the air cleaner. I let myself get thrown off track by the carburetor that was gummed inside, the fuel pump that worked but was too low in pressure, the fuel filter that was partially plugged, the fuel line that had debris in it and the gas tank that had to be boiled out because it was so full of debris and “goo”. And of course you made me aware of what an Idle Solenoid was. Yes, it now was as simple as taking out the air filter. The air filter appears to be the final problem with the engine. It runs and idles perfectly. What a joy. I am using K&N air filters in my other two cars, and the changes there have been remarkable.  When I put a K&N in my 1978 Fiat it ran just as strong as the day I bought it over thirty years ago. The K&N in our Camry noticeably improved the gas mileage. So, now I will be putting a K&N in the Datsun. I ask for your forgiveness, and allow me to remain with Ratsun.

 

29452744524_4befbf3955_b.jpgDatsunProjectCollage by Donald Broz, on Flickr

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