Weber 38 electric choke operation

[caz]

Hello!

I am working on a truck with a weber 38 with electric choke. The problem is, I am not exactly sure how it works when functioning properly.

When I first got the truck, the choke was closed all of the time and the choke was not receiving 12V (blown fuse).

It is now wired to a switched power source and I adjusted the choke (rotated the white plastic piece and set the high idle) so that it works great both cold and warm.

I pump the gas once to set the choke and now the truck starts and runs good when cold, and the high idle works fine. The problem is that the moment I hit the accelerator after it is running the truck will return to low idle - which is not ideal when it is cold.

What exactly does the electric part of the choke DO? Seems to me that there is some sort of bi-metal spring in there that controls the choke flapper itself.

What controls the high idle and is there an adjustment for how long the high idle stays engaged?

Thanks,
Andy

 

[76technician]

The electrically-heated bimetallic strip in the choke acts as a timer, since it takes about 4-5 minutes for it to warm enough to open the choke. If it's already warm (engine recently run) it will take less time to open. This is different from the coolant-operated choke in that it doesn't really have anything to do with actual engine block temperature.

It sounds to me like it's running as designed, which I agree isn't great if you want to be able to drive off as soon as the high idle smooths out. That's easier to do with a manual choke where you can ease off on the choke bit by bit as you drive away.

 

[JohnnyC]

there is the fast idle screw under the choke assembly... you can turn the plastic housing for the choke by lossening the three set screws to adjust the tension of the choke to stay open

i have my fast idle kick down right away... its always been that way ... never adjusted it

alot of people goto advance auto or auto zone or any other parts store and they make the weber a manual choke ... its a choke conversion kit... dorman makes it?

 

[76technician]

I could be wrong (it's been a couple of weeks since I was messing with it) but I think the high idle adjustment only changes the idle speed. Looking at the cam that it rides on I think any tap of the gas will turn it off.

I've been tempted to do the manual conversion, I always preferred being able to turn the choke down before the electric seems to want to. Luckily on my rig half the time it will start right up without using the choke at all (no gas pedal tap before starting).

 

[caz]

So,

Next question.

Would you expect the high idle to work when the truck has been sitting all day and the temp is 70 degrees with the sun on the hood?

It did not.

 

[Poser]

Not necessarily.

 

[brian]

i dont even have the choke hook up on my two.

 

[Weber Sarge]

You don't have enough tension set on the plastic section if it kicks off too easily in cold weather . That setting is a bit tricky , but when correctly set you should be able to start the engine and drive it immediately without any issues when letting off the throttle . If it wants to chug , you've set it too far (tight) and need to back off (loose) about 1/4" of travel on the adjustment . If the engine wants to die the first time to try to let it idle the choke isn't set rich (tight) enough . Wait for a good cool morning to set the high idle speed , that screw is located at the fuel bowl end below the choke element . Never start a Weber dead cold and walk away for too long when letting the engine warm up - you may return with it screaming at 2500 since it's either electric or water element will wind the choke blades off to lean the engine - but the mechanical linkage will not release the high idle setting until the throttle is used to snap it loose off the cam .

BTW- that manual choke conversion kit is junk , just leave the electric element on it and adjust it correctly . As long as it's set right and no vacuum leaks that carb should run and respond as well as efi - not kidding .
Sarge

 

[JohnnyC]

BTW- that manual choke conversion kit is junk , just leave the electric element on it and adjust it correctly . As long as it's set right and no vacuum leaks that carb should run and respond as well as efi - not kidding .
Sarge

Funny you mention this

Friends have converted to manual like... Just recently I tried it for the first time ... I have had water and electric chokes on webers but never manual... I picked up the kit that friend told me to get ... Put it on and found it was finicky ...

Maybe I'm older now or use to it or even lazy ... Or all the above

I missed the electric choke and put it back after only one day lol

 

[Weber Sarge]

I've had to remove quite a few of those manual conversions , never kept one of them and they all hit the trash can . The electric element choke is the way to go , one lousy wire and I've seen only 1 actually burnt out - they do not fail and are amazingly reliable .
Sarge

 

[caz]

Got it working very well with the electric choke. Still seems a little strange as to when the high idle works and when it does not but runs perfectly otherwise!

Thanks all for the tips.

 

[Boaf 32]

i dont even have the choke hook up on my two.

I installed my Weber 38 / 38 and did not connect the electric choke. When I start it, just as Caz says, pump it once, it sets the fast idle and close the butterfly.

I drive away and the fast idle goes away. The butterfly remains closed until warm, and then opens. Do you really need to connect the electric choke?

Boaf

By the way @brian, the 38 / 38 starts right away, not like my 32 / 36 manual choke.

 

[Dizzy]

The electric choke does this thing where the butterfly gets cracked open with engine vacuum, iirc, for enough air at cold operation, but not fully vertical for a hot engine's air need; the Aisan has an equivalent choke breaker that also trips the fast idle. I don't know if the temp from the engine is operating your electric choke? If you have a wire that once operated your Aisan's anti-dieseling solenoid, then you have a source for juice. If you are concerned about the Weber shorting, install an inline fuse or relay switch on the 'Engine' circuit of your harness.

 

[rousning]

Hi guys, does any you can help me with some pics, i have a weber 38 but i don't know how to wire the electric choke

 

[Dizzy]

Hi guys, does any you can help me with some pics, i have a weber 38 but i don't know how to wire the electric choke

Sorry, no pics. Just wire it to the 'engine' circuit. It could be the original idle cut solenoid wire. If you don't have that available, the low voltage on the coil will work.