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720 idle cut solenoid


wivrrat

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Just new to your forum.  Was googleing carburetor's for my 83 king cab 4x4 when I came across your blog.  Read a topic on google where advise was given to another carb problem, and the idle cut solenoid was mentioned.

 

Described the solenoid as a ticking sound behind the carb.  I have been hearing the ticking sound several times with the hood open.  Never knew where it came from or what it was.  My truck does not idle when cold.  I have to sit in the cab and keep the accelerator depressed to keep it running.  Once it warms up it idle's ok. 

Do I have a faulty solenoid????   The ticking is present without the engine running.  Comes and goes.  Goes for ever sometimes.

 

Sure glad I found out what was making the sound.  Now I need to know what to do.  Do I need to replace it?  

I also noticed when I had this truck smogged a couple years ago, a small piece of wood stuck in the carb holding the choke open.  I asked the smog mechanic if it should be removed and fixed and he stated removing it would cause a problem and to fix it means replacing the carb?

 

Sure glad I found this blog, as this truck is new to me.  I drive a 81 rabbit diesel pickup & 91 jeep cherokee also, and have worked on those over the years, now I need to learn some basics on this one.  Love the truck and its performance.  Sorry about the lengthly topic.  Any help will be appreciated.

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Described the solenoid as a ticking sound behind the carb.  I have been hearing the ticking sound several times with the hood open.  Never knew where it came from or what it was.  My truck does not idle when cold.  I have to sit in the cab and keep the accelerator depressed to keep it running.  Once it warms up it idle's ok. 

Do I have a faulty solenoid????   The ticking is present without the engine running.  Comes and goes.  Goes for ever sometimes.

 

Sure glad I found out what was making the sound.  Now I need to know what to do.  Do I need to replace it? 

The idle cut solenoid closes off fuel to the idle circuit when the ignition is turned off. It should only click when turning the ignition ON or OFF. It shouldn't click at other times. To test it, with engine off, listen near the back of the carb and have someone turn the ignition on, off, on, off. (don't start) you should hear a click that matches the 'on, off'.

 

You say you hear a clicking sound under the hood.... BUT was this with the engine running?

 

 

I also noticed when I had this truck smogged a couple years ago, a small piece of wood stuck in the carb holding the choke open.  I asked the smog mechanic if it should be removed and fixed and he stated removing it would cause a problem and to fix it means replacing the carb?

I doubt he was a mechanic, as the choke can easily be fixed or replaced without removing the carb or replacing it. He was just a smog weenie. The reason it won't run properly when cold is because the choke has been made nonoperative with a piece of wood.

 

 

 

NOW about your carb....

 

Unfortunately you have the electronic feedback carburetor in California. It will have a large round electrical plug at the back with 6-7 wires on it. These are notorious for the wires breaking inside the insulation because Nissan didn't make the wires long enough to be able to flex properly.

 

One of these wires is for the choke heater. If this isn't making contact the choke will never warm up and turn off.... perhaps this is why someone placed a piece of wood in the carb to hold it open?

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Sounds logical.  I talked with a mechanic yesterday and he is going to look at it.  I did look at the electrical plug and wires, will have to take the air filter housing to get a better look.  I agree, a good mechanic should have been able to fix the choke.

 

Thanks for the feedback.  As to the ticking sound, I haven't heard it for awhile.  Just sounded like a loud clock behind the carb/air filter and did it for hours.   I'll do your suggestion and have someone turn the ignition on and off to duplicate the click.  Thanks again.  Now I feel a little better maybe not having to replace the carb. 

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Well, I took the forums advice and asked a mechanic to check out the carb.  He had a helper who specialized in carbs.  Anyhow, they found a bad 2 prong plug-in connector behind the carb and said the carb was not getting a correct voltage from the battery. Corrected that.    Long story, short,  it ran great.  I've been driving it for about 3 weeks and about 800 miles without the stick.  Then yesterday, after a 150 mile drive in 90' heat I pulled up to a stop sign and it died.  Re-started it and every time I pulled up and stopped, it died.  Got it home and once it cooled down and the choke closed a bit, it started and continued to run.  Also, heard the ticking sound again in the carb.  Hadn't heard it since it was fixed.  Sounds like a timer tick.  I've got a problem.  My mechanic is in Mexico on vacation and I am scheduled to drive the truck back east this Tuesday.  May have to find another mechanic to check it out.  I put the stick back in the carb. 

Any suggestions as to what is causing this now?  

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hey, there, Newbie -

 

Our feedback carb is probably pretty similar to yours.  Take a look thru this thread and see if any of it helps.  Assuming of course that yours is similar, if not identical. 

 

Your idle cut solenoid might be working intermittently.  That might explain idling some of the time and not others.  The idle cut solenoid fails closed.  In other words, the little spring will try to shove that pin into the idle circuit and stop the flow of gas thru the carb.  If you put power on a functional idle cut solenoid it will pull the pin back and allow fuel thru the idle circuit.  According to what datzenmike told me, the ECU controls the voltage to the idle cut solenoid, so one thing to try would be using a multimeter to see if you get 12V on the red idle cut solenoid wire when you turn the key on.  If you're getting power, that means the ECU is sending the correct signal to the idle cut solenoid (ICS).  After that, you could extract the ICS very carefully (do not drop that tiny spring or plunger!) and test it on the bench.  See if 12V pulls the pin back into the solenoid body.  With no power, the spring should push the pin back out.  I repeat - don't drop those tiny parts.

 

Using a long, narrow object you can reach inside the round carburetor plug and gently pry the two little barbs inward on any one of the terminals, then slip the wire out of the plug.  To reinsert, gently pry the barbs back out, then push the wire fully into the plug.  Tug it backward a little bit to see if you pried the barbs out enough.  Those terminal ends are made out of flimsy metal and will not tolerate much abuse.  You don't want to break the barbs off. I would get the ICS wires out of the plug before trying to unscrew the ICS.  If you don't, you'll put a lot of twist into the wires before the ICS unthreads. 

 

If everything appears OK, blast some carb cleaner down deep into the cavity that accepts the ICS.  There might be dirt in the passageway.

 

The ICS is not readily replaceable.  Our local parts stores showed the device on their computers, but no availability.  I found a guy on eBay selling "new" ones for $80, but you could take your chances with a couple of swap-meet Hitachis for that price.

 

While you've got the air cleaner off (I get tired of taking off all those clamps, don't you?) you should check to make sure that the choke wire is getting 12V too.  The truck has to actually be running for the choke wire to get 12V.  "Key on" isn't enough.  Even if it takes a helper stomping on the gas, get the truck running for a few minutes, then blip the throttle.  The choke plate should pull all the way back to vertical within 5 minutes or so.  If the linkage appears to be gummed up, spray it down with some citrus solvent or similar and work it back & forth until it seems to move freely.  The mechanism that pulls the choke open is not capable of powering through a bunch of old grease and dirt.

 

The ticking time bomb noise you describe is the fuel/air ratio solenoid.  As you can see from that thread, I have not yet determined whether something's wrong with the solenoid itself, something's wrong with the ECU, or if that's the way it's supposed to work.  I'm guessing the ticking is not normal.  Our truck has done this since I can remember.

 

EDIT:  I don't know what the more knowledgeable folks would have to say, but jamming a piece of wood in the throat of your carburetor sounds like a recipe for disaster to me.  I think the first thing I'd do is get that out of there, then get the truck running and see if the choke opens.  If it does and you can drive it, drive it until it quits on you again, then whip the air cleaner open and see if the choke has gone shut.  If it has, you know what killed the truck, and you know what needs to be fixed. 

 

Will the choke go shut once the truck is up to operational temps if the ECU stops sending 12V to the choke's bimetallic spring?  I don't know.  The ECU under the seat may be going haywire.  It's an electronic device, and it can fail just like anything else.  It's not hard to get at.  Pictures of ours in the "Son of Idle Switch" thread.  Also, datzenmike lists some CA parts numbers in this thread.  You would want to find a CA unit if you want to be sure everything's gonna work as it should.

 

So, to sum it up, you have 3 - well, at least 3 - different things going on.  Different, but related because of the ECU. 

 

- The idle cut solenoid is supposed to pull back when the key is turned to run.  The ECU sends the voltage to the solenoid. 

- The choke could be inoperative, or more likely from what you describe, working intermittently.  I'm pretty sure the ECU sends the choke voltage too.

- The fuel/air ratio solenoid in the front of the carburetor is making that ticking noise.  Is it supposed to tick?  I don't think so.  Is it ticking because the solenoid itself is failing, or because the ECU is failing? 

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Checked the truck out this a.m.  Choke is back half closed and continuous clicking sound.  Started the truck and it started fine but is back to idleing rough again.  When it stopped yesterday, I did pull the air cleaner cover off and the choke was wide open.  It would start but wouldn't idle.  Once it cooled down and the choke started closing a little, it started and ran rough.  I'll take it to a shop in the a.m. and give them the comments on this blog.  As I stated, it ran fine for 3 weeks and approx 800 miles.  Ran great for the first part of a 300 mile trip yesterday, but cut out about 30 miles from the end of the trip.  Thanks for the info

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Maybe the repair described in post #7 didn't hold?  Is it basically doing exactly the same thing as before the repair?  Just going by what I've read on this forum, it sounds like damage to those wires at the plug is fairly common.  If I thought that was a problem with ours, I'd probably be looking at rounding up some heat-shrink tubing and some appropriate wire, then soldering in a few extra inches of wire between the plug and the carb.

 

You're saying the choke was half-closed this morning before firing off the truck, right?  If so, you've found one thing to work on.  I'm guessing there's more than one thing that's not working right.

 

Maybe someone will chime in and give us a definitive answer about the ticking.  I'd like to know.  Our truck runs, and it's ticked for as long as I can remember.  To me, that doesn't mean everything's OK. 

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