Fuel Pump; Fuel System Tests - Kohler 6600 Series Service Manual

Fuel System
Typical carbureted fuel system and related components
include:
● Fuel tank.
● Fuel lines.
● In-line fuel fi lter.
● Fuel pump.
● Carburetor.
Fuel from tank is moved through in-line fi lter and fuel
lines by fuel pump. Fuel then enters carburetor fl oat bowl
and is drawn into carburetor body and mixed with air.
This fuel-air mixture is then burned in engine combustion
chamber.
FUEL RECOMMENDATIONS
Refer to Maintenance.
FUEL LINE
Low permeation fuel line must be installed on carbureted
Kohler Co. engines to maintain EPA and CARB
regulatory compliance.

FUEL PUMP

Some engines use a pulse style fuel pump. Pumping
action of pulse style pumps is created by oscillation of
positive and negative pressures within crankcase. This
pressure is transmitted to pulse pump through rubber
hose connected between pump and crankcase. Pumping
action causes diaphragm on inside of pump to pull fuel
in on its downward stroke and to push it into carburetor
on its upward stroke. Two check valves prevent fuel from
going backward through pump.

FUEL SYSTEM TESTS

When engine starts hard or turns over but will not start, fuel system might be causing problems. Test fuel system by
performing following test.
1. Check for fuel in combustion chamber.
a. Disconnect and ground spark plug leads.
b. Close choke on carburetor.
c. Crank engine several times.
d. Remove spark plug and check for fuel at tip.
2. Check for fuel fl ow from tank to fuel pump.
a. Remove fuel line from inlet fi tting of fuel pump.
b. Hold line below bottom of tank. Open shut-off
valve (if equipped) and observe fl ow.
Condition
Fuel at tip of spark plug.
No fuel at tip of spark plug.
Fuel fl ows from fuel line.
No fuel fl ow from fuel line.
Fuel line condition.
30
Performance
Minimum fuel delivery rate must be 7.5 l/hr. (2 gal./hr.)
with a pressure at 0.3 psi and a fuel lift of 24 in. A
1.3 l/hr. (0.34 gal./hr.) fuel rate must be maintained at
5 Hz.
Fuel Pump Replacement
NOTE: Make sure orientation of new pump is consistent
with removed pump. Internal damage may occur
if installed incorrectly.
To replace pulse pump follow these steps. Note
orientation of pump before removing.
1. Disconnect fuel lines from inlet, outlet, and pulse
fi ttings on fuel pump.
2. Remove screws and take off pump.
3. Connect pulse line to new fuel pump and make sure
opposite end is properly connected into valve cover.
4. Attach new fuel pump using screws. Torque screws
to 2.8 N·m (25 in. lb.).
5. Reconnect fuel lines to inlet and outlet fi ttings and
secure with clamps.
AUTO CHOKE (if equipped)
If engine is equipped with Smart-Choke
identify design and follow appropriate troubleshooting
procedures starting on page 35 of this manual.
3. Check operation of fuel pump.
a. Remove fuel line from inlet fi tting of carburetor.
b. Crank engine several times and observe fl ow.
Fuel is reaching combustion chamber.
Check fuel fl ow from fuel tank (step 2).
Check for faulty fuel pump (step 3).
If fuel pump is working, check for faulty carburetor. Refer
to Carburetor.
Check fuel tank cap vent, fuel pickup screen, in-line
fi lter, shut-off valve, and fuel line. Correct any observed
problem and reconnect line.
Check for a clogged fuel line. If fuel line is unobstructed,
check for overfi lled crankcase and/or oil in pulse line. If
checks don't reveal cause of problem, replace pump.
KohlerEngines.com
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Conclusion
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