Weber choke fast idle problems

[matrophy]

The choke and/or fast idle on my new 32/36 Weber is acting funny. 

 

This is a carb that gave me nothing but trouble initially and I am not sure that the fast idle was ever working right.

 

Right now, if I blip the throttle before starting with the engine dead cold, the choke slams shut and there is a gap between the throttle adjusting screw and the throttle lever as if the fast idle is engaged correctly.

In order to start the engine, I  have to pump the throttle a few more times while cranking. Somehow after doing this, the fast idle linkage must be clicking off and there is no longer a gap at the throttle screw. Once the engine starts, the engine idles at 500 rpm requiring lots of pumping of the accelerator to stay running. Once the engine warms up, it idles at around 800 rpm and stays at that idle for the remainder of the time.

 

I've tried blipping the throttle twice before turning the key to maybe get more fuel into the carb so it starts right away but that doesn't seem to help the engine start without cranking and pumping the accelerator.

 

I blipped the throttle up to 4 times just now with the engine off and cold and the fast idle linkage seems to be working OK with a gap at the idle screw still.

Somewhere in the process of cranking and pumping, the fast idle is disengaging so there's no fast idle.

 

It seems like either, I'm not following the correct procedure when trying to start the engine or, maybe there's something wrong with the fast idle adjustment.

 

Am I supposed to pump once or twice before starting and then hold the throttle partway open while cranking - rather than pumping the accelerator while cranking?

 

I've done plenty of searching to find info about adjusting the fast idle and haven't found anything comprehensive enough to cover this issue

 

 

 

 

 

 

[datzenmike]

If extra cold I give it extra pumps. The accelerator pump squirts raw gas in and makes it fire sooner.

 

The fast idle is allowed to engage when the choke is on. There is a linkage between them. With engine cold watch what happens when the choke closes. The fast idle cam lifts up into position and holds the throttle partly open. If it's coming off too soon maybe the choke is also coming off too soon. You can bend the fast idle linkage to be on more.

[matrophy]

Should I also be pumping the accelerator as I'm cranking, leave it alone, or hold it partway open?

[datzenmike]

 

 

Hold the throttle half open and with your hand, close the choke flap and watch what happens when the choke closes. There is a vertical linkage going down to the fast idle cam.

 

 

[matrophy]

On 9/18/2021 at 1:42 PM, datzenmike said:

 

 

Hold the throttle half open and with your hand, close the choke flap and watch what happens when the choke closes. There is a vertical linkage going down to the fast idle cam.

 

 

When I do as you describe with engine dead cold, when I open the throttle, I can hear the linkage click and the choke slams closed. There is a gap at the throttle screw of about 1/4".

 

I'm not sure what you mean by 'watching what happens when the choke closes' because the choke is closed at  that point.

 

In any case, the choke seems to be working OK when the engine is cold before the engine starts. I pumped the accelerator several times to get fuel sprayed into the carb before trying to start the engine and doing so allowed the engine to start without pumping the accelerator.

 

The engine started and idled around 1500 rpm. I'm not sure if that's too high.

 

Once I blip the throttle, the fast idle stops and the rpms drop to around 500 rpm until the engine warms up and it idles fine at around 800 rpm.

 

This is the same thing that is happening while I'm cranking the engine. By the time it starts after several pumps of the accelerator, I think the fast idle is disengaging.

 

What I think might be happening is that the cam of the fast idle is at it's minimum height when cold so a few pumps of the accelerator and slight movement of the choke plate causes the fast idle to disengage.

 

I can't see the cam with the carb on the engine so I'm just guessing.

 

I wonder if I should adjust the choke so it is higher on the cam when cold? I marked the location of the choke housing when I installed the carb and it is still set at that point. 

 

How large of a gap should there be at the idle adjustment screw when cold and choke engaged?

[datzenmike]

I meant to look at the fast idle to see how or if it was setting. But if the idle is 1,500 that's perfect.

 

Don't 'blip' the throttle. This will engage the choke unloader function and defeat the choke and fast idle. The whole point of the fast idle and the choke on is to warm the engine as soon as possible and be drive able when the engine is cold.  Start and either let warm up or start driving right away. No sense wasting gas sitting there it will warm even faster when being driven.  

[matrophy]

6 minutes ago, datzenmike said:

I meant to look at the fast idle to see how or if it was setting. But if the idle is 1,500 that's perfect.

 

Don't 'blip' the throttle. This will engage the choke unloader function and defeat the choke and fast idle. The whole point of the fast idle and the choke on is to warm the engine as soon as possible and be drive able when the engine is cold.  Start and either let warm up or start driving right away. No sense wasting gas sitting there it will warm even faster when being driven.  

Understood. Seems like something is wrong because the fast idle disengages while cranking the engine cold and pumping the accelerator. The workaround right now is to pump the throttle several times before attempting to start - my theory being that doing so fills the carb with fuel via the accelerator pump - and not touching the throttle until it idles a few minutes under fast idle. I can do that if that's how it supposed to be done but it doesn't seem normal - whatever normal is.

 

Maybe this engine is just cold-blooded. I have no frame of reference because when I first got this truck, the choke was inoperable and the gas had to be pumped several times when starting and babied until it idled well. There was no fast idle. It was a PITA on cold Oregon mornings for sure. I kind of expected that swapping the Weber would solve this.

[datzenmike]

The procedure would be to step on the gas to set the choke and by extension this sets the fast idle also. As it gets colder it helps to step on it 2 or more times. Then foot off the gas, start engine. Pumping the gas while starting is likely to turn the choke off.

 

The choke is adjustable. Have a look on the housing, usually has arrows pointing towards richer or leaner. Try loosening screw(s) and twisting richer but note where it is so you can return it if you have to.

[matrophy]

40 minutes ago, datzenmike said:

The procedure would be to step on the gas to set the choke and by extension this sets the fast idle also. As it gets colder it helps to step on it 2 or more times. Then foot off the gas, start engine. Pumping the gas while starting is likely to turn the choke off.

 

The choke is adjustable. Have a look on the housing, usually has arrows pointing towards richer or leaner. Try loosening screw(s) and twisting richer but note where it is so you can return it if you have to.

I assume ccw is richer?

 

BTW - Don't know if you're a Breaking Bad fan or just like the meme but we just re-watched the whole show for the 3rd time and it gets better every time I watch it. The best and most perfect TV show ever - IMO.

[datzenmike]

Hold the throttle open and try each way. Leaner will eventually turn the choke off completely. I don't know which way is what on a Weber.

[matrophy]

On 9/20/2021 at 3:24 PM, datzenmike said:

Hold the throttle open and try each way. Leaner will eventually turn the choke off completely. I don't know which way is what on a Weber.

Here's a follow-up. I adjusted the choke about 1/8" richer (which is ccw). With 3 pumps of the accelerator and then foot off the gas, it fired right up and idled at 1200 rpm. I may adjust the fast idle up a little. Thanks for the help. I do believe I'm out of projects on my truck now.

[Figbuck]

L20, new 32/36 Dgev through California Datsun,

 

Dead cold, I turn the ignition on. Step on the throttle once. Crank for a second, fires and idles at 1200. If the ambient temp is cold, I let it warm up for 20 or 30 seconds, drive off. Then engine warms pretty fast. It doesn't hesitate or stall at all.

 

Dead cold on a warm day, It fires off and drives right off too.

 

On cold starts, if I let it sit... it will  high idle forever until I blip the throttle.

 

On warm starts, I never touch the throttle, just stab the starter. If it doesn't catch the first time... it does the second time.  I think because the fuel pump cycles.

 

No extended cranking, or pumping the throttle at all. Idles nice at 800rpm all day long.

 

I will have to look again, but I don't think there is any gap when the choke is closed.

Edited September 23, 2021 by Figbuck

[matrophy]

2 minutes ago, Figbuck said:

L20, new 32/36 Dgev through California Datsun,

 

Dead cold, I turn the ignition on. Step on the throttle once. Crank for a second, fires and idles at 1200. If the ambient temp is cold, I let it warm up for 20 or 30 seconds, drive off. Then engine warms pretty fast. It doesn't hesitate or stall at all.

 

Dead cold on a warm day, It fires off and drives right off too.

 

On cold starts, if I let it sit... it will  high idle forever until I blip the throttle.

 

On warm starts, I never touch the throttle, just stab the starter. If it doesn't catch the first time... it does the second time.  I think because the fuel pump cycles.

 

No extended cranking, or pumping the throttle at all. Idles nice at 800rpm all day long.

 

I will have to look again, but I don't think there is any gap when the choke is closed.

Pretty sure there's a gap if it idles at 1200 when you first start it

[Thomas Perkins]

On my 85 720 4x4 2.4.on a cold start in the morning.I turn the ignition on,step on gas pedal and let go, then start engine,then engine cranks,rpm's goes to 2000,then I tap on gas pedal,rpm's goes to 1100 rpm's,then I tap gas pedal again,then it goes to 850 rpm's and idles there all the time.On a warm start,I turn key,tap gas pedal and it fires up.I've had my Weber for years.I also use a idle cut off solenoid.It says to adjust your fast idle screw to 2000 rpm's.You can adjust it when the engine is warm or cold,if you do it when it is warm,take air filter cover off,push throttle by hand all the way,then close the choke  with other hand,then crank up,check rpm's,if not at 2000,then turn engine off,turn fast idle screw clockwise,then do the same thing,push throttle by hand and close the chock,then restart and check rpm's,if not at 2000,then repeat till it is.