Yanmar 4LHA-HTP User Manual

Chapter 3 Fuel Injection Equipment
6. Fuel Feed Pump
4LHA Series
((
Automatic pressure control mechanism
As the delivery pressure of the fuel pump climbs,
the pressure at the back of the piston also rises, over-
coming the piston spring force, and hindering the
lowering of the P iston. Thus, the fuel flow automatical-
ly stops, and the fuel pressure is maintained within
a fixed range.
Outle
Inside chamber
Inlet
Inside chamber
J
Outside chamber
Outside chamber
6-2 Fuel Feed Pump Disassembly
Follow the procedure below to disassemble the fuel
feed pump.
(1) Remove the piston spring stopper plug, and pull
out the piston and piston spring.
(2) Remove the snap ring, and pull out the tappet
assembly.
(3) Pull out the inter-spindle.
(4) Remove the priming pump.
(5) Remove the discharge valve spring stopper, and
remove the valve and spring from inside.
(6) Remove the O-ring.
6-3 Fuel Feed Pump Inspection
(1) Block the priming pump with your finger and
check whether the pressed-in piston returns by
spring force. If the piston returns, the piston does
not have enough negative pressure. Always replace
the priming pump as a set.
(2) Check the piston spring for cuts, cracks, uneven
wear and rust.
(3) If the piston, inter-spindle, or tappet assembly are
extremely worn, replace the part.
(4) Check the contact surface of the valve and valve
seat for defects.
(5) When there is play in a valve seat which has been
calked into the feed pump body, the whole fuel
pump body must be replaced.
Inlet
I
Inside chamber
Outside chamber
1
Outlet
At rated pressure rise
When the outside chamber pressure
overcomes the piston spring force,
the piston is pushed up and separated
from the push rod.
NOTE: Play in the valve seat hinders the opening and
closing of the valve, causing insufficient fuel
supply and abnormal wear of the tappets and
camshaft.
6-4 Fuel Feed Pump Reassembly
(1) To reassemble the fuel feed pump, follow the as-
sembly procedure in reverse order.
(2) When the pump has been reassembled, perform
the air-tightness test.
Apply 0.29(3)MPa(kgf/cnn) of air pressure to the
discharge outlet of the pump, and check for air
leaks from the O-ring. If air is leaking, replace the
O-ring.
Measuring cylinder
Tappet - -c^z^LJ -~" z:
Blocked
Air pressure MPa (kgf/cm
1
)
Container filled
with diesel fuel
V'
3-2-41

Yanmar 4LHA-HTP Specifications

General

Brand	Yanmar
Model	4LHA-HTP
Category	Engine
Language	English