Bleeding Fuel System; Fuel Feed Pump; Injectors - Sisu Diesel 320 Workshop Manual

C. Bleeding fuel system
Note! This fuel system removes automatically small
amounts of air bubbles from the filter and the pump when
the engine is running. However, bleed the system always,
when the system has been opened or fuel has been
exhausted during driving or a new spare pump has been
fitted (to avoid long starting time).
1. Pump by hand the fuel feed pump lever. If the pumping
seems to be ineffective, turn the engine a little so that the
camshaft cam is not at the feed pump lifter.
2. Loosen the bleeding screw A on the filter. Pump with the
hand pump until no air bubbles flows out of the bleeding
screw hole. Tighten the bleeding screw.
3. Pump further with the hand pump and loosen the fuel
inlet connection B on the pump, until the fuel coming out is
free from air bubbles. Tighten the connection.
4. Start the engine and assure, that no leaks exist.
Note! When the bleeding is done in this way, fuel flows
immediately into the internal transfer pump when the starter
motor is rotating and the distributor pump housing is filled
quickly with fuel. In the pump housing there is a stop sole-
noid, which must not be switched on for longer periods
when the pump housing is empty of fuel.
Fuel System
213--- 45
A
B
213--- 46
D. Fuel feed pump
For the membrane type fuel feed pump no spare parts are
supplied. The feed pump must be changed for a new one,
if the feed pressure has dropped noticeably (min. 0,20 bar/
max. rpm) or if the fuel feed pump has been damaged.
Note! From engine number H 6794 have engines provide
with new type fuel feed pump. New pump is fixed to cylin-
der block with four screws instead of the previous two. The
new pump can be used as spares also to earlier made en-
gines using repair kit 8366 62052, see Service information
no 50 98.
Measuring fuel feed pressure
--- Clean the injection pump, filter and all fuel pipes.
--- Connect a pressure gauge between the filter and the in-
jection pump, connect the pressure gauge to the inlet pipe
in the middle of the injection pump rear end (point B in the
previous instruction).
--- Allow the engine to run at the idling speed and read off
the fuel feed pressure in the pressure gauge.
Note! If the feed pressure value is below the rated value,
possible reason can be:
--- blocked fuel filter/fuel feed pump metal gauze filter
--- faulty fuel feed pump
--- blocked or leaked fuel pipes or pipe connections
Important! Under the fuel feed pump cover there is a
washable filter. If much impurities have gathered on this
filter, fuel cannot flow to the feed pump and further to the
injection pump and this causes malfunctions in the fuel sys-
tem. Always when malfunctions appear, the feed pump
cover should be removed and the metal gauze filter must
be checked and cleaned.
E. Injectors
Injectors are checked and serviced according to instruc-
tions 13 L...O on pages 13 ---13...13 ---15.
Opening and setting pressures of the injectors are on page
14 ---10.
Adjustment is achieved by changing the shims. The thick-
ness of the shims varies from 1.00...1,90 mm and they are
available in increments of 0,05 mm. A thicker shim will raise
the opening pressure while a thinner one lowers it. A differ-
ence in shim thickness of 0,05 mm changes the opening
pressure by approx. 5,0 bar. As the opening pressure of the
injector drops slightly after adjustment, the opening pres-
sure should be set to approximately 10 bar above the value
given in the specifications. This value applies both to new
and used injector.
13---25