Skoda 105 s 1980 Workshop Manual page 66

d )
e )
f )
choke plunger sticking in its bottom
position
storting worm engine
too high fuel level in floot chomber
incorrectly odiusted idle run
unstick the plunger or reploce it with
o new one
o d j u s t t h e f l o o t
odiust idle run correctlY
2.2O FUEL PUMP
Technicol DescriPtion
The model JIKOV MF 3407 fuel pump is of
the diophrogm ond lever type, controlled by the
round disc of the comshoft. The suction motion
of the diophrogm is octuoted by the lever, the
dischorge motion by the spring of the dio-
phrogm. Fuel flows through o stroiner, o mud
trop, ond the suction volve to the delivery
volve. A priming lever is provided for hond
p r i m i n g o f t h e f u e l . T h e m o v i n g m e c h o n i s m i s
l u b r i c o t e d w i t h o i l s p l o s h e d f r o m t h e c y l i n d e r
b l o c k .
S t r o k e o f t h e d r i v i n g d i s k
4 m m
Suction heod
1.5 mm
D e l i v e r y h e o d .
2 m m
Pump dischorge ot 2,000 strokes
per minute ond free outflowwithout
counter-pressure
30 ltrs/hr.
Mointenonce, Repoirs, Disossembly
ond Reossembly
For routine mointenonce (cleoning of the
mud-trop screen) see Chopter 15.3. After hoving
operoted the hond-priming lever lift it till it
engoges sofely in its locked position.
ln the cose of o defect, inspect the diophrogm
ond check the volves for leokoge. After hoving
removed the pump from the engine, remove the
mud trop, seporote the upper port from the
lower port, ond remove two screws, holding
down the thrust plote, to lift owoy the volves.
Swill oll ports in petrol ond blow off with com'
pressed oir. Reploce domoged ports with new
ones.
lf necessory, remove the diophrogm from the
octuoting lever in the lower port of the fuel
pump (its monufocturer recommends the dio-
phrogm to be reploced ofter obout 50,000 kilo-
rnetres with o new one). Do not stretch the
spring of the diophrogm ond do not olter its
compression force chorocteristic in ony woy.
Do not forget to put fibre pocking rings under
the volves when reossembling the fuel PumP.
Put o spocer ring under the suction volve (close
to the mud trop). Fig.2.2Ol1 shows the pos-
itions of volves ond the holding-down thrust
p l o t e .
P u t t h e s p r i n g o f t h e d i o p h r o g m i n t o t h e
lower port oi the pump ond engoge the pin ot
the diophrogm with the octuoting lever. Oper-
ote the hond lever to compress the dioPhrogm
oncl hold it in position by inserting o rod of 4.5
to 5 mm diorneter (for exomple the shonk of
o drill, etc.) between the octuoting lever ond
the woll of the pump lower Port.
Now bolt both pump ports together so thot
the mud trop is on the right-hond side when
viewing the pump from obove ond the fostening
flonge from the front. Use spring woshers
u n d e r t h e c l o m p i n g b o l t s .
Fig.2.2011 - Section Through Fuel Pump
lf it is necessory to verify the dischorge of
the pump by o test, note the following require'
mentswhich the pump must meet otl80strokes
per minute:
o) 15 ltrs/hr. ot f ree outf low without fuel
counterpressure
b) minimum pressure of 0.018 MPo (1.8 m of
woter column) ot o zero off'toke of fuel
c) o dry pump must drow fuel from o depth of
1.5 m in 16 seconds.
Fuel Pump Defects ond Their Removol
1. Foulty fuel supply
o) clogged mud trop
b) domoged diophrogm
2. Fuel pump does not hold fuel
o) dirty or defective volves
c l e o n i t
reploce it with o new one
wosh them in petrol, reploce defective
volves with new ones
66