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  • February 26, 2024, 12:43:36 PM

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Author Topic: What causes carb to move to fast idle position? Choke thermostat?  (Read 4829 times)

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Offline MIPS

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #30 on: November 28, 2022, 08:43:46 PM »
Okay, for your reference, here I am with a cold engine and one pump on the pedal. Choke is closed and the throttle is sitting at the top of the high idle cam.




Here is the same carb after 30 minutes of driving. The choke has unloaded completely and is being held open by the thermostat.




In neither set of the photos was the engine running, so there is no pull-off.
Here is also my thermostat. I cannot remember if I scribed the line in the housing or if that was there already but you can see how mine is positioned relative to the marks on the casting.
(ignore the unplugged wire. I did that so you could better see things)



Here is what the same carburetor, fully adjusted, will do on a cold start, choke closed and with a completely empty bowl. Note the throttle tap to pop if down to the second cam step.
(link is timestamped to 56:06)

https://youtu.be/FB6MZLUBskQ?t=3366

Quote
Is there a document from the TSM or elsewhere that outlines all the conditions when the SolVac operates?
In detail is is not listed however it is described as part of the "Idle Control System" at http://amceaglesden.com/guide/1J_-_Fuel_Systems on page 1J-101.

In short:

-The vacuum kick is only controllable by the computer using the Vacuum Switching Valve, or VsV. The computer can use it to extend the pushrod so that the solenoid idle kick will engage on its own.
-The solenoid idle kick is controlled by the Idle Speed relay in addition to the rear defroster, air conditioning and headlights using a group of diodes to prevent current backflow.
-The solenoid idle kick is not strong enough to extend the pushrod by itself against the tension of the throttle return spring. You need to either open the throttle slightly or use the vacuum side to extend it.
-The solenoid idle kick can remain on for an indefinite amount of time and the coil will not burn out

A Sol-vac with a vacuum leak cannot be operated by the computer on its own.
A sol-vac with a bad solenoid will not maintain a high idle for accessory loads/the computer and is more likely to stall at curb idle.
« Last Edit: November 28, 2022, 08:46:01 PM by MIPS »

Offline 86Woodgrain

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #31 on: November 29, 2022, 11:15:00 AM »
Thanks for the help guys! Thanks for the offer to help in person MIPS but that's too far to go in my jalopy LOL

Update, today was -11C (12F) upon first cold start this morn. I simply pumped the gas twice and then cranked, although I looked under the hood after the first pump to check the choke valve (it was closed), the thing did fire up after cranking for about 7 seconds straight. Not bad, I guess I was too impatient with the pedal pumping and cranking before. I even think I could get away with one pump of the pedal and then crank in the future, we'll see, I will experiment.

I feel like my choke thermostat issue is resolved at this point.

The one thing that was very different today is that the car was on a higher idle mode for my whole city drive of about 30 mins. The fast idle cam was off, it seemed to be 100% on the elevated idle due to the SoleVac. It's strange having the higher idle when cold, I haven't experienced that before. I kind of expected the higher idle but I didn't expect it for my whole drive. I thought it would go away after 5-10 mins but I guess not.

The way I read the SoleVac operation is I might have this elevated idle all winter long, because it says if the air temp is below +13C it will give vacuum assist to the SoleVac and bump idle up. Page 1J-38 from that link MIPS posted.

UPDATE: I put it in the garage and popped the hood. The idle was still elevated and when I looked the engine hadn't come off the very top step of the fast idle cam just yet. Now I suspect the choke thermostat is not coming off fast enough, even though it is working. I am going to think about it but I might swap in one of the other thermostats I have... hmm....
« Last Edit: November 29, 2022, 02:13:48 PM by 86Woodgrain »

Offline MIPS

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #32 on: November 29, 2022, 02:16:55 PM »
If the air cleaner temperature is too cold (TAC switch) that will make the computer hold a high idle until the air cleaner warms up. Closed loop and curb idle isn't allowed until the coolant switch and the TAC are satisfied. The TSM section 1J link above lists this as one of the multiple open-loop modes near the end of the chapter. The idea is that doing so runs the exhaust manifold hotter and the warm air diverter will be open, so the engine will be pulling warm air in from around the hot manifold and not the front of the car.
This whole time, the choke thermostat is independently controlled. IIRC the schematic says the electric choke is operating as long as you have oil pressure, so if you were wondering, nothing I said above would affect the operation of the choke.

Here's a fun experiment. Run the engine until warm, then disconnect and plug the line to the warm air diverter actuator. If it's really cold out the engine in short order will bump the idle after a few minutes. Now go for a drive and try accelerating. Every time you give that poor carburetor a blast of air the engine will absolutely fall on its face.
« Last Edit: November 29, 2022, 02:20:34 PM by MIPS »

Offline 86Woodgrain

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #33 on: November 29, 2022, 02:31:30 PM »
Is this where I admit that the pipe from the exhaust manifold isn't 100% connected to the air cleaner due to constantly taking it off and testing? I'll hook it up tight.

Man there are so many things that need to be just right to make this carb work I can understand why my brother keeps telling me to just swap it with a Motorcraft LOL but I'm up for a challenge instead! If it's all fixed right then it should run great.

I checked for continuity on the SolVac 12V and it was good.
« Last Edit: November 29, 2022, 02:35:26 PM by 86Woodgrain »

Offline MIPS

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #34 on: November 29, 2022, 02:36:34 PM »
That's an easy mistake.  The challenge is installing and removing the air cleaner a dozen times and not totally mangling the end of the pipe, or in my case, getting the pipe on but not noticing the actuator had become unhooked.   :P

Quote
I checked for continuity on the SolVac 12V and it was good.

Weird. Okay for our sanity and because it's two screws take the Sol-Vac off and try powering it directly from the battery. Is the pushrod still not extending and latching?
« Last Edit: November 29, 2022, 03:04:09 PM by MIPS »

Offline 86Woodgrain

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #35 on: November 29, 2022, 04:26:39 PM »
I took the SolVac off, tried to clean it all as best I could. I pulled the rubber dust boots back and sprayed a little WD40 in there and worked it back and forth to try and make sure it is able to move if it wants to.

After doing that, it's a little sluggish to extend using vacuum. Doh, it may be a bit flaky there I'm not sure time will tell. I can't see how lubing it and operating it manually would cause that to happen.

So I took it right to the battery and when 12V is directly applied it moves a tiny bit and stops the thing from going back, when I put it back on the carb (car off) and apply 12V it basically stops the rod from moving in any direction. So with 12V applied car off I tried screwing in the end adjuster but in the end it bottomed out and won't go out further. I tried pushing and pulling on the adjuster screw at the end and it won't budge at all with 12V applied.

I also tried moving the throttle linkage open to give the SolVac a chance to extend with 12V directly applied and it just seems to stop where it is, it doesn't extend out any further.

I feel today like one step forward, two steps back.
« Last Edit: November 29, 2022, 04:27:17 PM by 86Woodgrain »

Offline 86Woodgrain

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #36 on: November 29, 2022, 04:36:11 PM »
I applied 12V and just keep tightening that screw again, it seemed to really bottom out.

I can confirm without 12V the thing moves in and out freely by hand. It does push forward to a point when 12V is applied, but even with the throttle held open it will not ever go to a point to ever boost the throttle above idle. It would need a combination of vacuum applied AND 12V to ever get far enough IMHO. The vacuum side can push the idle up but not 12V alone.

Offline 86Woodgrain

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #37 on: November 29, 2022, 04:50:32 PM »
Well I think we should just forget about the 12V SolVac now. I think it's totally buggered, the screw doesn't screw anything in or out. I kept turning it in when I felt resistance since I had nothing to lose. Oh well.
« Last Edit: November 29, 2022, 04:55:22 PM by 86Woodgrain »

Offline MIPS

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #38 on: November 29, 2022, 05:06:16 PM »
Actually that all sounds good. It only moves the pushrod at most 1/8". It only needs to open the throttle a tiny amount.

Gleebledorf can explain it better and he has more detailed instructions on testing https://gleebledorf.com/solvac.html


Before you pull all your hair out and get more frustrated, reset the idle adjustments per the TSM since you bottomed out the solenoid adjustment screw and lets leave it alone. This won't affect the choke and you can continue to run the rest of the winter without it making your life miserable. This can be dealt with when it's warmer out. (you can also mail the Sol-vac to me and I'll test it for you. I don't mind. :) )

Actually, now that I remembered Gleebledorf exists, he has a whole page dedicated to your original question which was the electric choke. His whole site might make your browser complain it's insecure but he probably forgot to renew his certificate again.  https://gleebledorf.com/choke.html
« Last Edit: November 29, 2022, 05:21:47 PM by MIPS »

Offline 86Woodgrain

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #39 on: November 29, 2022, 05:58:45 PM »
Actually that all sounds good. It only moves the pushrod at most 1/8". It only needs to open the throttle a tiny amount.
It doesn't move enough to even reach the Sole-Vac vacuum adjustment screw. In other words it used to move a tiny bit before I wrecked it but it was never enough to bump the idle up even if I opened the throttle so it had room to extend.

I had seen those articles a long time ago, I will look them over again.

I did doubly-check the curb idle and SolVac vacuum idle speeds again today, they are OK.

I think I need to shop for a replacement SolVac. I shot a short video during my work this afternoon, I will upload it and post back so you can see exactly what I'm trying to describe (I hope LOL).

Edit: Video is uploading now, link is @ https://youtu.be/zJNPljYjwA0
« Last Edit: November 29, 2022, 06:00:17 PM by 86Woodgrain »

Offline Illeagle1984

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #40 on: November 29, 2022, 06:50:06 PM »
I offer my used sol-vac if you'd like it, and any other emissions parts I removed from IllEagle.  MCU, complete harness, solenoid bank.  I don't want to ever use it, but I can't bear to throw away that kind of stuff...
It's getting crowded down here:
1973 Ford Mustang "Rustang"
1984 AMC Eagle Sedan "IllEagle" 183k
1984 AMC Eagle Wagon "Eagle 2"
1996 Cadillac Eldorado 178k
1998 Oldsmobile Eighty-Eight 239k
2002 Cadillac Eldorado Doral Edition
2005 Chevrolet Silverado 1500 179k

Offline MIPS

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #41 on: November 29, 2022, 08:55:45 PM »
Edit: Video is uploading now, link is @ https://youtu.be/zJNPljYjwA0
Give me a few hours and I'll go get a video cooked up for you. From what I see it looks fine but I'll make something you and anyone else can compare with.

Offline 86Woodgrain

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #42 on: November 29, 2022, 09:41:50 PM »
Now that I’ve been thinking about it I’m mostly wondering if you apply 12V to your SolVac does it actually push out far enough to bring the car above idle? You’d have to manually opene the throttle. Mine doesn’t come out far enough to bump idle even when I hold the gas open.

Offline 86Woodgrain

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #43 on: November 29, 2022, 09:46:39 PM »
I offer my used sol-vac if you'd like it, and any other emissions parts I removed from IllEagle.  MCU, complete harness, solenoid bank.  I don't want to ever use it, but I can't bear to throw away that kind of stuff...
I may take you up on that. Do you have a way to vacuum test the SolVac? Otherwise I may be interested in the CTO valve with the vacuum ports on it, the temp sensor on the back of the air cleaner and that’s basically it. I’m not sure if the vacuum thing on the intake can be removed without a leak?

Offline MIPS

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Re: What causes carb to move to fast idle position? Choke thermostat?
« Reply #44 on: November 30, 2022, 12:55:47 AM »
Here. Hopefully this is detailed enough to explain what you should be seeing.

https://www.youtube.com/watch?v=9i-lUwsrDNk
« Last Edit: November 30, 2022, 12:56:27 AM by MIPS »

 

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