I
I
FIGURE
12-1
COMBINATION GAS- GASOLINE SYSTEM,
K662
A t idle s p e e d , the velocity of a i r t h r o u g h a c a r b u r e t o r m a y not be high enough t o d r a w sufficient
f u e l t o s u s t a i n o p e r a t i o n .
F o r t h i s r e a s o n , s o m e c a r b u r e t o r s h a v e a n idle l i n e which c a r r i e s a c e r t a i n
a m o u n t of f u e l f r o m the s e c o n d a r y r e g u l a t o r t o the a i r intake s i d e of the c a r b u r e t o r w h e r e i t i s i n t r o -
duced a t the l o w e r i d l e s p e e d s . When f u e l d e m a n d d r o p s t o a c e r t a i n point, the r e g u l a t o r d i v e r t s f u e l
f r o m the m a i n f u e l s y s t e m i n t o the idle f u e l s y s t e m . On c a r b u r e t o r s with this s e t u p , the idle m i x t u r e
a d j u s t m e n t i s m a d e a t the r e g u l a t o r r a t h e r than a t the c a r b u r e t o r .
The t h r o t t l e valve within the c a r b u r e t o r r e g u l a t e s the r a t e of a i r flow t h r o u g h the c a r b u r e t o r .
When a n engine i s a t top s p e e d , t h i s valve is wide open and o f f e r s l i t t l e r e s t r i c t i o n t o a i r flow. Closing
the t h r o t t l e c a u s e s a d e c r e a s e in
flow a n d l o w e r s engine s p e e d and
p o w e r .
A s the valve c l o s e s .
p r e s s u r e builds up behind the valve which r e d u c e s p r e s s u r e t h r o u g h the v e n t u r i and p a s t the f u e l nozzle.
The r a t i o of a i r t o f u e l i s t h u s k e p t f a i r l y c o n s t a n t a t v a r y i n g s p e e d s .
The d i a p h r a g m type u s e s a d i a p h r a g m a c t i v a t e d a i r - g a s valve t o p r o p o r t i o n the flow of a i r a n d
g a s . A m e t e r i n g valve i s linked t o the d i a p h r a g m , t h e r e f o r e t h e g r e a t e r the a i r flow, the g r e a t e r the
valve opening and a c o r r e s p o n d i n g i n c r e a s e i n intake of g a s . S i n c e the valve was opened only by a
vacuum c r e a t e d b y p a s s a g e of a i r , i t c l o s e s c o m p l e t e l y when t h e engine is stopped.
On e n g i n e s with the g a s o l i n e c a r b u r e t o r , a n a d a p t e r i s i n s t a l l e d b e t w e e n the c a r b u r e t o r and a i r
c l e a n e r . The a d a p t e r c o n s i s t s of a g a s j e t and v e n t u r i . A c c u r a t e m e t e r i n g of the g a s i s a c c o m p l i s h e d
by load and s t a r t i n g o r idle a d j u s t m e n t s c r e w s in the body of the a d a p t e r .
On s o m e o t h e r s y s t e m s , a b a l a n c e l i n e i s u s e d t o avoid the p r o b l e m of
f u e l m i x t u r e
which c a n b e c a u s e d by r e s t r i c t e d a i r flow due t o a clogged a i r c l e a n e r .
The b a l a n c e l i n e i s connected
t o
a t m o s p h e r i c s i d e of the s e c o n d a r y r e g u l a t o r a n d t o the c a r b u r e t o r a i r h o r n . T h i s b a l a n c e
i n s u r e s a c o n s t a n t r a t i o of f u e l t o a i r u n d e r v a r y i n g d e g r e e of a i r c l e a n e r r e s t r i c t i o n .
OPERATING INSTRUCTIONS
-
GAS FUELED ENGINES
B e c a u s e of t h e n a t u r e of the g a s e o u s f u e l s , a slightly d i f f e r e n t p r o c e d u r e should be followed
when s t a r t i n g and m a k i n g i n i t i a l a d j u s t m e n t on g a s fueled e n g i n e s . A d j u s t m e n t s v a r y a c c o r d i n g t o the
type of e q u i p m e n t u s e d . F o r e x a m p l e , the idle f u e l a d j u s t m e n t i s m a d e a t the s e c o n d a r y r e g u l a t o r on
s o m e s y s t e m s while on o t h e r t y p e s , t h i s
is
done on the c a r b u r e t o r . The d i f f e r e n t t y p e s of c a r b u r e t o r s
and r e g u l a t o r e q u i p m e n t a r e d e s c r i b e d i n the r e m a i n d e r of t h i s s e c t i o n . A d j u s t m e n t i n s t r u c t i o n s a r e
s t a t e d f o r e a c h type along with a b r i e f d e s c r i p t i o n of the o p e r a t i n g p r i n c i p l e s p l u s n e c e s s a r y s e r v i c e
and reconditioning i n f o r m a t i o n .
