Technical What's a black wire connected to RPM bolt in Weber 32/34 ?

[Artiom]

Hello again.
After a close inspection of my carburetor (i guess it's Weber 32/34 TLDE) on my Tempra 1.6. I have noticed that i have a loose wire that in one end it's connected to the carb. to the RPM adjusting bolt it seems. And the other end is not connected at all. Could it be some kind of sensor ?
(I am strarting to hate those guys at the garage, next time i fix my car on my own ! if u want something done right , do it yourself )

 

[fiat1100d]

I don't remember my Tempra having such a wire connected to the bolt for regulating the idle RPM: you are referring to it, aren't you?

 

[maddogmorg]

black wires are usually earth wires though could be a dirty striped wire. it may be a throttle stop wire though that's not the idle rpm screw bit i don't think. i think that it's to do with the fuel cut out module. though not entirely sure.

 

[Artiom]

Yes , i meant the idle RPM bolt. The wire is connected right to it.

 

[Artiom]

Fuel cut out ? what's that ? and if it's connected to the ground how it can cut off someting ?

 

[maddogmorg]

i found a black wire and it goes round the carb to the back left hand side where it connects to a yellow wire.

the fuel cut out module is just what it says it is for if you crash and to stop overrun apparently.

 

[ben743]

Hi,

That black wire is not Ground, nor does it have anything to do with fuel cutoff in case of an accident.

This wire senses when the driver does not press the accelerator pedal. Note that the idle speed screw that this wire attaches to is in a plastic housing which isolates it from the carburetor body. When the pedal is not pressed the accelerator lever rests on the idle speed screw, thus grounding the wire. When the pedal is pressed, the lever no longer rests on the screw and the wire is disconnected from the electrical ground (battery minus).

This wire comes from leg 4 of the Digiplex 2 ignition control unit. You count the legs from the left when you are facing the Digiplex unit). For easy identification note that legs 1 and 2 are unused.

Basically, when the car is moving with an RPM above idle (I do not remember exact numbers), but with the accelerator pedal not pressed (like going down hill), the Digiplex control unit reduces the amount of fuel used by deactivating the electromagnetic valve on the side of the carburetor (this valve connects to leg 6 of the Digiplex unit).

In short this is an accelerator pedal position sensor used to save fuel when free rolling down hill.

Benjamin

 

[fiat1100d]

I just noticed that also my Tempra has that wire after I got the carb cleaned, I confirm the end of the wire is in a plastic housing.

Thank you Benjamin for your post, your knowledge is incredible!