Page 111 - Mechanic Diesel - TT
P. 111
MECHANIC DIESEL - CITS
3 Cruising Circuit
4 High Speed or Full Throttle Circuit
5 Accelerating Pump Circuit
6 Chock Circuit
Float Circuit: It is very important to keep the level of petrol in the float bowl constant at all times. If the level
increases too much, more petrol will go through the jet into the manifold, which will increase fuel consumption
and if the level decreases, less petrol will come out of the jet, due to which the engine will not be able to develop
full power.
A float ball and needle valve are installed to keep the level of petrol in the bowl full.
The fuel pump will keep supplying petrol with pressure while the engine is running, whether the carburetor needs
less petrol or more. We have just read that we have to keep the level of petrol in the float bowl full. To keep the
level of petrol constant, float ball and needle valve are installed which work in the following manner.
The float ball is a hollow ball from which the air is removed. It rises when the bowl is filled with more petrol. As it
rises, the needle valve which is stuck with the bowl’s lever, rises up. When it rises up, the needle valve sits on its
seat, which closes the way for petrol to enter the float bowl.
When the float goes from the bowl to the carburetor through petrol jets, then along with the petrol level going
down, the float ball also comes down, due to which the needle valve again falls on the lever and the way for petrol
opens up and petrol starts coming into the float bowl. In this way, the level of petrol remains complete in the float
bowl.
Idle and slow speed Circuit: To run the engine slowly, we close the throttle a little. By closing the throttle, less
air can enter the venture, due to which less vacuum is created inside the venture. When the vacuum is less, the
main jet is able to draw less petrol from the float chamber, due to which the engine does not get the supply of
mixture to the entire surface and it stops. To run the engine at slow speed or idle speed, another circuit is required
through which we can put petrol in the carburetor through a jet at slow speed.
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CITS : Automotive - Mechanic Diesel - Lesson 29 & 30
