How to adjust a Weber electric choke

[The Scifi Guy]

What's the basic adjustment procedure for a Weber electric choke? How do they know the engine is warmed up, since they have no connection to the water or thermostat? Is it just a timed thing where the power going to the coil spring slowly opens the choke over the course of 5-10 minutes? How do I adjust it on my Weber 38?

When I start my buggy, the engine revs at about 2000 rpm when the choke is on, which seems way too high. Then, a quick smack of the gas pedal seems to totally release the choke and now the rpms are at normal operating rpms, which is too low if the engine isn't warmed up or it's cold out. I'm sure that I can adjust the characteristics of the choke function with those factory set screws that you're told never to touch. Should I be dickin' around with those? Do we have a thread that explains their adjustment?

[tomking]

There are threads Gordon, but dont know where. The FSM wants a cold idle RPM of 2800!! Yep. Should just let it warm up a few minutes and then you can click it off fast idle to regular idle. Slow down Gordy!

[yellaopelgt]

I'm not positive if this is the "correct" way to make the adjustment......but I just loosened the 3 screws around the choke housing and gave it a bit of a turn to where I felt the fast idle should be. The spring inside is attached to an arm that controls the butterflies and when heated by electricity, the spring opens(or closes...I forget). Not too complicated, just takes some playing around...maybe others will chime in with a better way??
HTH
Joe

[The Scifi Guy]

The FSM wants a cold idle RPM of 2800!!

Yeah, that's actually closer to the rpms it runs at. I misspoke saying 2000. Man, that seems awfully fast for a cold engine with all the oil drained down to the belly pan. Plus my exhaust is so loud and ferocious, my neighbors think a plane is taking off next door.

Slow down Gordy!

Impatience is a sign of youth and I'm still young at heart!

[hrcollinsjr]

There are threads Gordon, but dont know where. The FSM wants a cold idle RPM of 2800!!

I'm thinking if we drop a few more 'bread crumbs' more of the little birdies even the 'looney birds' will find them. Right, Gordon!

From Weber Carbs Direct:

Testing the Automatic Choke adjustment.
The choke is preset at the factory but in some cases it may be necessary
to readjust.
The choke assembly must be cool ( below 68 F 20C) before attempting to
make any adjustments. First fully rotate the throttle lever and release;
Check for smooth operation; the choke plate should be all the way closed.
Make a reference mark on the carburetor and the choke where the two faces
meet. Loosen the three 7mm hex head screws one full turn. While holding
the throttle about one third open, adjust the closing tension on the choke
plates just fully close; then slightly increase the tension on the spring by
continuing to rotate the thermostat 1/8" measured in the outer diameter of the
thermostat. Tighten the three 7mm hex head screws without distorting the
retainer ring; fast idle speed may need to be readjusted.

This obviously would have to be done on a cold engine. With that being said, fast idle is set when the engine is warm. Run engine to normal operating temp, shut it off, manually work the choke making sure the fast idle screw is on the highest step, start engine without moving the throttle, thus moving the choke and releasing the fast idle, set idle at ~2800 rpm per FSM. This seems a bit high to me so I tend to set it at 2700 rpm and call it good.

Harold

P.S. If I lost you somewhere, holler at me and I'll try to walk you through it.

[hrcollinsjr]

Impatience is a sign of youth and I'm still young at heart!

Gordon, sounds like a 'learning disability' to me. They have 'pills' for that!

Harold

[The Scifi Guy]

Okay. So, how does an electric choke work and respond to engine temperature? Or does it? I remember being able to SEE the choke slowly open as the engine warmed up when I had a water choke. I don't recall seeing that happen since I switched to an electric choke. Is this because I don't have it adjusted right?

[hrcollinsjr]

It is a 'timed' event, it doesn't open in relationship to engine temp as you've probably already guessed.
Is the choke receiving 12v upon engine start? I guess I should have posted a link to where I copied the troubleshooting info from but a quick search should turn up the pdf file that I copied from.

I guess you could have the choke far enough out of adjustment that it wouldn't move. I know of at least one person on this list, I'll not mention Mach1's name , but his choke isn't connected to a 12v source and he's adjusted it to keep the choke flap open at all times.

Harold

Edit: Posted link in my first reply as I should have done to start with.

[tomking]

Gordon, sounds like a 'learning disability' to me. They have 'pills' for that!

Harold

And they have blue pills for what ails you Harold
Gordon I too dont set my speed that high, rather around 2000 instead.

[wrench459]

Okay. So, how does an electric choke work and respond to engine temperature? Or does it? I remember being able to SEE the choke slowly open as the engine warmed up when I had a water choke. I don't recall seeing that happen since I switched to an electric choke. Is this because I don't have it adjusted right?

Gordon is your choke is opening too fast?
If so you can add a ballast resistor for slower opening.

[RallyBob]

I'm guessing the tension on the bimetallic element (and therefore the choke plate) is too high.

You're supposed to adjust it so that you can fit an 1/8" drill bit between the choke housing and the edge of the choke plate with basically zero tension on the bit. I see many people just crank up the tension on the element which keeps the choke plate tight against the housing. This will drastically increase the time before the engine goes off fast idle.

[opelbits]

What Bob said...

In the old days (when people knew about such things), you had winter and summer choke settings. This was really just a matter of increasing or decreasing the tension on the choke to compensate for faster/slower opening rates due to high or low ambient temperature.
What many did to set the choke was to do it in the morning (coolest part of the day with cold engine) just like in Harold's Weber Carbs Direct directions. Also, the faster the choke opens up or the lower the rpm, the less fuel you use to warm up the car. It really doesn't take long to warm up the motor to the point of it idling on it's own.
Two things that affect that the most are hooking up the electric choke to the coil (resistor wire feeding coil means less than 12v! Common mistake when switching to an electric choke Weber...ask me how I know...) and also anyone using a 160* thermostat will be increasing their warm up time.
Electric chokes should ease off on their own for tha most part. Too much tension on the spring or a sticking choke mechanism (all the little cams and such that connect the choke to the throttle not being lubed sufficiently) with keep things in place until you hit the throttle.

[The Scifi Guy]

If Bob's mention of an 1/8" gap is true, then it's likely that I have it adjusted too tight. It definitely opens up all the way eventually. There's no huge problem with the car's running, I just started this thread to make sure I had it set right and to see if that 2800rpm starting idle was normal or excessive.

Tom, you mentioned that you like to keep the rpm's closer to 2000. That sounds like an experiment worth trying. What screw do I adjust to achieve that? Or am I going to have to get out the vacuum gauge, timing light, EKG machine, and my random anomoly generator?

[RallyBob]

What screw do I adjust to achieve that? Or am I going to have to get out the vacuum gauge, timing light, EKG machine, and my random anomoly generator?

See the screw to the right of the choke element in this picture? It's above the brass vacuum tube. That's the fast idle speed adjustment.

[wrench459]

... Or am I going to have to get out the vacuum gauge, timing light, EKG machine, and my random anomoly generator?

Just for you I'll bring the scope home and get the voltage and current ramps
of the electric choke.

[The Scifi Guy]

Just for you I'll bring the scope home and get the voltage and current ramps
of the electric choke.

Yeah! And let's convert it to 120VAC! More power is always better, right? The car will warm up 10 times faster and the choke will oscillate between open and closed at 60 cycles!

Bob, do I have to soak the screw in water for a few weeks so it's nice and rusty like in the picture?

[hrcollinsjr]

Gordon, the fast idle speed given is for a warm engine! When you first start a cold engine it won't be that fast unless you are like a few I know that want to start their cars and go back in until the frost is melted off. That works much better on FI cars that will idle down on their own. Carburetored engines with mechanical chokes need someone to tap the throttle pedal to bring it off of the highest step on the fast idle cam.

Harold

[tekenaar]

See the screw to the right of the choke element in this picture? It's above the brass vacuum tube. That's the fast idle speed adjustment.

Yeah! . . .

Bob, do I have to soak the screw in water for a few weeks so it's nice and rusty like in the picture?

. . . required part of the adjustment procedure!

[wrench459]

As promised for my buddy Gordon!
White housing, made in Japan, 38 DGAS choke heater current ramp. 10 ohms@ 83 F.

[The Scifi Guy]

Gordon, the fast idle speed given is for a warm engine! When you first start a cold engine it won't be that fast unless you are like a few I know that want to start their cars and go back in until the frost is melted off. That works much better on FI cars that will idle down on their own. Carburetored engines with mechanical chokes need someone to tap the throttle pedal to bring it off of the highest step on the fast idle cam.

Harold

Actually 2800rpm IS the where mine idles at when I start it cold. Pardon me for being a dumb-ass, but THERE'S A SECOND LEVEL? I'll be darned if I've ever noticed it. I smack that pedal and it goes right down to the warmed up idle speed. Are those two levels independently adjustable? Or does that screw raise/lower both points simultaneously? The carb came from former member Jeff Van Dyke(His Opel is R.I.P.). He seems to have been a tinkerer, maybe he altered the stock adjustments. I'm curious.....I always give the pedal a good squash after about 10-15 seconds to kick off that "high" cold start idle. Does doing that disengage the fast idle cam function entirely? Would a lighter touch maybe bring me down to a not-as-fast-level?