FUEL SYSTEM
Fuel Feed Pump Components and Functions
6-30
6LY3 Service Manual
© 2007 Yanmar Marine International
Fuel Feed Pump Specifications
Disassembling the Fuel Feed Pump
1. Remove the piston spring plug and pull out the
piston and piston spring.
2. Remove the retaining ring and pull out the roller
guide, roller pin and roller.
3. Pull out the inter-spindle.
4. Remove the priming pump.
5. Remove the discharge valve spring plug.
Remove the valve and spring.
6. Remove all O-rings.
Inspecting the Fuel Feed Pump
1. Block the priming pump with your finger and
check whether the pressed-in piston returns by
spring force.
2. If the piston returns, the piston does not have
enough negative (-) pressure. Always replace
the priming pump as a complete set.
3. Check the piston spring for cuts, cracks, uneven
wear and rust.
4. Replace the piston, inter-spindle or tappet if
extremely worn.
5. Check the contact surface of the valve and
valve seat for defects.
6. When there is play in a valve seat which has
been sealed into the feed pump body, replace
the entire pump body.
NOTICE: 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.
Assembling the Fuel Feed Pump
1. Position the discharge valve and spring in the
fuel feed pump housing. Lubricate and install a
new O-ring on the discharge valve plug. Install
the discharge valve plug.
2. Lubricate and install a new O-ring on the
priming pump. Install the priming pump.
3. Position the piston and piston spring in the fuel
feed pump housing. Lubricate and install a new
O-ring on the piston spring plug. Install the
piston spring plug.
4. Install the inter-spindle.
5. Position the roller guide, roller pin, and roller in
the fuel feed pump housing. Install the retaining
ring.
6. When the pump has been reassembled,
perform the air-tightness test. Apply 0.3 MPa
(3 kg / cm
2
) (43 psi) of air pressure
(Figure 6-37, (2))
to the discharge outlet of the
pump and check for air leaks from the O-ring. If
air is leaking, replace the O-ring.
Figure 6-38
Figure 6-38
1 – Measuring Cylinder
2 – Air Pressure
3 – Container Filled with Light Oil
4 – Blocked (Plugged)
5 – Tappet
Item
Standard
Maximum Suction Head of Fuel Feed Pump
1.0 m (3.2 ft)
Maximum Discharge Volume of Fuel Feed Pump
11.4 L / min. (3.001 gal.)
at camshaft speed 1500 rpm,
engine speed 3000 rpm
Maximum Discharge Pressure of Fuel Feed Pump
230-370 kPa (2.3-3.8 kgf / cm
2
) (33.3-53.6 psi)
at camshaft speed 1500 rpm,
engine speed 3000 rpm
(1)
(5)
(4)
(2)
(
3
)
0005701
