Hi,

I bought this car 3 years ago, and the automatic choke was disconnected.
I decided to put it back as i think it's better "as original"

I changed :
- Fuel & Air : Carburetor Choke Thermostat / Heater : https://www.rockauto.com/?carcode=1035492&parttype=6004
- Fuel & Air : Carburetor Choke Thermostat / Heater : https://www.rockauto.com/?carcode=1035492&parttype=6000

And i repluged the Wire Carburetor Choke Heater that was unpluged, and remove an extra wire that was put before to maintain the little shutter open (!!!)

Car succeded to start has always , but i have now always the choke light on . How to troubleshoot the trouble as i don't know how it is originaly.
The little shutter is open and the big one is closed, even when car is hot.

Thanks for your help


Camaro Z28 choke always on

 

Small valve on top of front 2 barrels = choke
Large valve on top of rear 2 barrels = secondary air valve

The sec air valve should stay closed at all times that you can possibly see it, except if you open it with your finger. Its function is involved only with the secondaries (the big 2 rear barrels) and is only a factor when your foot is on the floor at relatively high RPMs, like passing on a 2-lane highway or something.

The choke should close when the engine is COMPLETELY cold (let's say, below 20°C or so), after you open the throttles fully ONCE. Let the engine cool fully (tomorrow morning), take off the air cleaner, get in the car, depress the throttle, get out, look, verify.

The choke thermostat/heater is a "bi-metal" coiled spring, made of 2 different metals in layers, one on the inside of the coil and one on the outside, with an electric heating element attached to it. Being 2 different metals, they expand and contract differently as the temperature changes, making the spring stronger or weaker. function of the is to close the choke by way of spring tension when it's cold, then the heater warms it up which reduces the spring tension and eventually all the tension goes away. The spring closes the choke, then when it heats up, opens the choke. BUT: if the Choke light is on, that means that power is not being supplied to the heater, meaning that the choke will stay on FOREVER. The choke heater circuit and the alternator circuit are interconnected such that the choke heater gets power applied to it ONLY when the alternator is charging. Which means that if the engine is not running, or if the alt is not working for whatever reason, the choke will stay on FOREVER.

The choke light is on for one of 3 reasons:

C/H (choke heater) fuse is blown
Gages (sic) fuse is blown
Alternator is not working

Verify that the choke and air valve behave as described, then check the 3 possible culprits for the Choke (alternator) light coming on. If it isn't working by then, come back and we'll point you onward.

 

Hi,
Thanks for this complete reply i have three questions on your message :

1°) As my cars works for years and battery is charged, we can be sure Alternator is working ? (think yes)
2°) As i changed the bi metal spring, in which position should i turn it (when car is cold and t° outside less than 20°C) ? I turn it until shutter us closed due to the force of spring ?
3°) As i have not Under the hand the fuse box description so i don't know where are the C/H (choke heater) fuse and the Gages (sic) fuse. Are they inside near driver legs fuse box ?

Thanks a lot for all you learn me !

Best Regards

 

1. Probably. Definitely maybe but maybe not. You'll need to figure that out.
2. The spring has a hook in the end. It's supposed to engage a prong on a linkage piece inside the "bowl". It's possible that when you put it on, you didn't get that assembled right. When you put it on, you will have the round black piece turned whichever way it needs to be to let the pieces hook up inside there, then you will turn it counter-clockwise until the "Rich/Lean" mark on the round black piece lines up with the center mark on the "bowl"..
3. Yes those fuses are in that fuse box. They are labelled "C/H" and "GAGES" (which of course is a misspelling of the word "gauges". I take no credit for the error.

 

Hi,

Thanks again !

1°) I re check today , but the alternator is working , 14,2V when beams on etc

2°) yes i checked when i put tre spring to put it's hook to engage a prong inside the "bowl". I don't have a "Rich/Lean" mark on the round black piece.
And i also don't have a line on the center mark on the "bowl".. should it be verticaly putted ? yesterday when installed it, it turned clockwise and not counter clockwise....
If this parts not aligned can stay the light "Choke on"'?
I turned it counter clockwisde until it close the small valve.

3°) i checked my fuse box see below, the fuse gauge is ok (seams i have a 20A instead of a 10A !) on the other one on top right, they are good.





4°) I check that 12V on the wire that arrives to spring. 12V in on when unplugged ! OK and when i plug it become 0V !

So i started the car and it runs at 1500 RPM , choke on, RPM doens't go down, shutter stay semi closed and chocke light is on.

I can't drive the car (because of virus ….) but if i let it "on site" without Driving" , motor become hot , but chocke stay activated.


Thanks again !

 

I took 2 Videos , i Don't know if it works when sharing the links :

https://photos.app.goo.gl/DVk2bvU1PXSMoLVD6

https://photos.app.goo.gl/jUcd7feEiusGN56w6

 

The schematic diagram for the choke and alternator circuit is in this discussion; scroll down to post #9.

https://www.thirdgen.org/forums/carb...et-timing.html

The one for your car is the V8 VIN "H" one.

Check the choke heater relay, which is in the "convenience center"; a little tray like thing right above your right knee when driving, that has the diagnostic connector on the end of it.

 

Thanks again for all your help !

i found the convenience relay box , and it seams (i didn't check yet) but it misses some relay, i have some slots free ….

 

I'm not sure what all is supposed to be, or not be, in there. It varies according to the details of the car.

The choke heater relay circuit is 3 wires; 2 are brown, one blue. Find those, verify that they go to a relay, that the relay is operated when the key is on and the engine not running, and that it drops out when the alt is charging. One of the brown wires (250) should have 12V on it whenever the key is on; the other brown wire (25) should be at ground with key on & engine off, and go to 12V with key on and engine running. If those voltages are there, then the circuit - wiring, alternator, fuses, etc. - is all working correctly, and the relay is bad.

Since the Choke light is on, I'm suspecting that you will find that wire 25 does NOT get 12V on it when the engine is running but instead remains at ground (since that is what lights the light), which would indicate an alternator or wiring problem. Probably the alternator. The alt could still be charging, but not putting the correct signal on that wire.

 

Hello again,

As i ordered 3 items to "repair/renew" my chocke , the third part was : The relay !

And it feets exactly in this missing slot !
As soon as i installed it, the choke on light goes off. (If i remove the relay, chocke light is on as before.) , there is now 12V on the spring even when plugged.

Now i have to wait tomorrow, to adjust spring to have front sutter off because now my motor is still a little hot and shutter is still open.

Then i will start the car and hope to see relay light on, then shut off …. after 4 or 5 minutes (if 15°c outside at Morning)

Am 'i exact ?

See u tomorrow !

 

Things often work better when they're installed... Do you have any idea why it was missing?

With the key on and engine not running, and the choke wire connected, the Choke light should be on, and the wire to the choke should NOT have 12V on it. As soon as the engine is started, the Choke light should go out, and 12V should appear at the choke. The choke should start out closed, then after a few minutes of the engine running, it should open by itself.

The correct way to start the car is to press the gas pedal to the floor once; for every 6 or 7° below 20°, pump it one more time; take your foot off the gas, and start the engine. It should require no more than a second or 2 of cranking to start. It should reach a high idle speed, probably 1200 RPM or so, within a few seconds of starting, and stay like that if left alone. After the choke has warmed up, which is usually only a minute or 2, if you gently rev up the engine slightly and then let off the gas, the idle speed should drop down to its normal setting.

It the car does all those things, then the choke is working correctly.

 

Hi,
It was missing because they had trouble with it, but i don't know more…
I have also the light " fasten belts" on. It's light comes a little down then flases slow after a moment…. Don't know if it's helps troubleshoot.

So :

I started the car this morning, when put ignition on, the light "choke on" does'nt light up, and i started the car as always. There was no realy starter,
I let the car all the day in the garage, the front shutter is not really closed at the end of the day , car "cold"
I think the move between "open" and close" in not an angle 90° , but near 20° ….

I have a question, does the "hook" on the picture below (at end of blue Arrow ) where there was the end of my screedriver, should not " hook" the green part below (red Arrow)
i think they are not hanged each others , but they just touch them by side.



Thanks for your help.

 

I do not want to hijack Scoody's thread, but I will try this to resolve my own issues. Thanks for telling us how to check the relay!

 

Hi,

In fact i have 12V on the blue wire and also on the two Brown when contact is on ,engine not running.
When i start engine, i have 14V on the three wires in the convenience box.

Seams one wire is not well connected in motor area (notice that electricity has been bad done on this car by previous guy) , so where should i start ?

Thanks for your help

 

Check the voltage on the brown wire at the alternator with the car not running and then after you start it.

 

Hi,

if you are talking about theses ones , 12V when car off, 12V when key turned , 9V when starting , then 14V when engine running.
These on both wires , the big red ,adn little Brown.


alternator 3td Gen Camaro



Thanks

 

Yes those are the right ones.

The alternator should ground the brown wire when it's not charging.

Sounds like you need an alternator. Or at least, the regulator, which is inside the alt. Maybe the brushes too if you go the regulator route, since those are what always physically wears out.

 

Ok it's clear !
So just to test my choke after this alt trouble , i can cut the Brown wire and put it to ground manualy to test when engine is running ?

 

No, don't cut anything.

You can use a pick or small screwdriver or something, to take the actual connector out of the plastic body.

The internals of the alternator should ground that wire when it is NOT charging, and put 12V on it when it is. When it's grounded it should light the "Choke" light on the dash and operate the choke relay, and the choke should NOT get 12V on the blue wire. When it's raised to 12V the light and relay should go back to their "rest" state and the blue wire should get 12V.

 

ok, i didn't cut the Brown wire, i succeeded to remove it from connector, and linked it with a wire to ground :

Choke light is on in car when contact, and i started the car normally , it seams i was at a little more of 1200rpm , and as i'm too much counter clockwise on the solenoid, it stays "high" running.
So i ordered an alternator to change it.
I have a question, so the 12V on the solenoid is sent how many times ? Always after motor started in fact ? What is it's use ? the solenoid becomes hot with motor and turns , or becomes hot with 12V on it ?

 

I'm going to assume you are asking about the thermostat, not a solenoid?

The 12V is there whenever the alternator is charging. Yes it gets rather warm and stays that way at all times. It's an archaic system; left over from when they used heat from the exhaust to do that, instead of an electric heater. It's a brute-force method at best. The heat should eventually open the choke and let the idle back down to normal after it gets hot.

 

So it's the 12V that makes the thermostat , turning the spring and opening the shutter to stop choke?
If i'm right the trouble i have with alternator not grounding Brown wire , should not cause trouble on choke as i had before 12V on the thermostat !
It's like the 12V on thermostat do nothing even if it's a new one …

Thanks

 

No, it probably would have worked OK as it was, but the alt was definitely bad and most likely would have quit working completely soon.

 

ok i follow your advice as i want it to work like it should.
But franckly if we remove all the system of alternator, relay etc etc and just put 12V on connector of thermostat, it should move and close shutter ?
I will wait more than one week to have the new alternator, so i want to troubleshoot all possible before.
I don't understand why it doesn't really moves the shutter event with 12V on it's connector….

Thanks

 

I need the same relay for my 85, ran into a similar issue - PO installed a horn relay instead of the correct choke relay. No wondering never went off!

I cannot quite make out the part.number of the relay from your pic. Would you mind posting the PN, and where you bought it? Does not seem to be at any of the local part stores.

 

From NAPA auto, might be part ECH AR740. That's the correct part for my '83 Z28

 

hi, my relay cames from rockauto : https://www.rockauto.com/?carcode=1035492&parttype=3016

 

Hello,

i finally received the new alternator yesterday, then installed it. Now i have my chocke light on when contact is on, then when engine is started ligh comes off.
The blue wire on alt, is 12V, then grounded, then 14,8V.
Seams now all is working as it should, but i don't really have choke when i start the car, i will try to counter clockwise turn a little more the thermostat.

In fact as i never got chock on my Z28 i don't knwo if now (wheather is good and not cold) it should really work for 1minute …. Can you tell me about your experience ?
Here the picture of my shutter when car is "cold" , is it enough closed ?

 

It should just barely close completely with very little tension when the outside temp is about 20°C or so, and as it gets cooler, the tension holding it closed should increase. If your thermostat is the adjustable kind, you can try loosening the screws and turning it counterclockwise to the point where it just closes the blades after sitting overnight. You will have to hold the throttle slightly open while adjusting it, since the fast idle cam should be up against the throttle linkage while doing that.

 

Should i make this while engine running or not ? So i have to counter clockwise more my thermostat… i will do it.

Thanks a lot for your (regular) help !

 

Engine not running, cold, holding the throttle slightly open.

Turning it CCW tightens it up... turn it CW first to let it get loose, then turn it CCW to bring it to the desired degree of tightness.

It may take several cold starts in the morning before you get it really dialed in. They were rather inconsistent from the factory since they didn't do anything like that, they just slapped them together and shipped them.

 

Hi ,
So i turn counter clock the thermostat until shutter is closed.
I started engine, it was running at 1000/1100 rpm .
I wait 2 mns then give a little acc kick , so it goes down near 800rpm.( shutter opens at 75°, not 90°)
Then 5 seconds later, the engine grows up to 1000/1100 rpm and shutter start to close …
I can make this test 4 or 4 times trouble is the same.
Seams like the amplitude of thermostat is not enough and too much tension also ….

Any idea ?

 

Measure the resistance from the blade on the thermostat that the wire hooks to, to a known good ground somewhere on the engine, such as the alternator bracket. Should be around 3 - 4 ohms.

 

3,3 ohms to the - of baterie and 3,6 to the outside metal part of alternator

 

With the engine running, is there 12V on the wire to the choke, with it plugged in?

If you let the engine run for a few minutes, does the choke get hot?

When you say "the shutter starts to close", then after it has been running, can you open it by hand with little or no tension on it?

 

YES

YES

yes with tension

 

Latests news :

With the blade closed at cold start , i have the choke working now, and after motor is hot and acceleration, the rpm goes down.
But it still runs at more than 1000rpm , and i try to turn the screw at Bottom , left from front of the carb, but in the two ways it seams to change nothing….
It seams i'm touching the right screw, why doesn't it goes up or down when turning screw ?
I there mixture screw on this choke model also to adjust ?

Thanks

 

Is the "E" cam should be able to move alone ? mine stays on top and Don't go down alone.
See video on link https://photos.app.goo.gl/Dfkcj9UNNc5qd4Jr9
When i move with my finger like thermostat would do,if i push until E cam comes UP , it never comes down again.
The other side of fast cam , on picture below, is it normal lime this ? https://photos.app.goo.gl/4gHSx4Mu7FCsD42HA

Thanks

 

The fast idle cam, which is the silver colored one between the green pieces, has the throttle resting on it when nobody is pushing the gas. If you do what you did where you set it in the upward position, then if the choke is hot or if you hold the blade open by hand, when you push the throttle, it'll drop back down on its own.

Yes the 2nd video looks normal. The little piece that only moves a small amount, is the secondary lockout link. It keeps the secondaries from opening when the choke is on. After all, you don't want the engine to be super-stressed by some moron drive getting into it and flooring it when the oil isn't flowing yet... because, you know, humans. All of that stuff down in there is tied in with the throttle shaft, the fast idle cam, the fast idle adjustment screw, and all that.

When the engine is running, that vacuum can at the front right of the carb, gets vacuum fed to it; and it pulls in. The green link bumps up against the choke linkage and opens the blade slightly. This should happen within 2 seconds or so after a cold start.

The choke system is very complex on these carbs, and very thoroughly thought through. It looks more complicated than it needs to be, but in reality, when it works right, it's excellent. It's almost impossible for the driver to perceive that it's operating. Ideally you should be able to get in, push the throttle once to let the choke set, let it idle long enough to put on the seat belt and select the correct radio station (because, well, humans), put it in gear, and drive away; and it should handle all of its own internal functions automatically. It's not easy to get it set up right though, because you can only do it when the engine is cold. It can take a few weeks of fiddling to get it just right.

 

Do i have to do this test while engine running ? i think so, just want to be sure.
=> I prefer to test before putting back air cleaner, because i find it's "hard" when pushing whith hands to have it fall down. I want to be sure he falls down.

So now how to adjust high idle and normal idle as when i turn the screw Bottom left front it makes Nothing (high or normal rpm) ?

 

No, you can do it with the engine off... hold the throttle partway open with your hand, and then all that linkage that seems stiff, should move freely, under the tension of the choke spring of course. But it won't feel like it's rubbing against something.

High idle (when the choke is on) is a little screw on the right side of the carb, underneath the choke thermostat, right up against the carb body, near the throttle shaft.

There are a couple of ways that the normal idle might be controlled. Since yours is an export model I'm not positive how it was done. One, is the screw at the left front of the carb, that the throttle comes to rest against. The other is the solenoid right next to that. The solenoid has different functions in different years, and may also be different in computer-controlled carbs from regular ones like yours. Look at it and see if it's extended, and the throttle rests against it, rather than the screw. If so, the plunger can be screwed in or out to adjust the idle.

 

ok clear, so i'm installing back the thermostat, i turn counter clockwise to have the choke blade near close, it moves the fast idle cam also "E" to top position.

If i push to bottom the fast idle cam with my finger, should the "spring" of the thermostat be able to move it up back ? . (all theses tests engine off, just resistance tests)

 

Yes. If the engine is cold enough that the choke should operate. While holding the throttle open with your 3rd hand of course.

 

Ok i succeeded to turn the screw to have the idle rpm lower, near 750 ( first time i lower from 1100 to 700 and engine hangs when engage gear and turning tires. So mount back to 750 or near seams better !!!

But when i started i had no choke at all , everything is well mounted back ….
What i imagine is as idle RPM was really to high before i didnn't see the difference before between the high idle rpm and normal rpm….
In what way should i turn the high idle screw to make the rpm higher ? Screw or unscrew ?
Seams it's my last trouble !!!

 

Screw in to make it higher.

 

Following all your advices and now it works like a charm !!!!

Sometimes in the Morning i don't have exactly the same rpm, but choke works now . So much thanks to @sofakingdom

 

Great thread!!