5.2
Section 5
Fuel System and Governor
Fuel System Tests
When the engine starts hard, or turns over but will not start, it is possible that the problem is in the fuel
system. To find out if the fuel system is causing the problem, perform the following tests.
Test
Conclusion
1. Check the following:
a. Make sure the fuel tank contains clean, fresh,
proper fuel.
b. Make sure the vent in fuel tank cap is open.
c. Make sure the fuel valve is open.
d. Make sure the fuel lines to fuel pump are
secured and in good condition.
2. Check for fuel in the combustion chamber.
a. Disconnect and ground spark plug leads.
b. Close the choke on the carburetor.
c. Crank the engine several times.
d. Remove the spark plug and check for fuel at
the tip.
2. If there
is
fuel at the tip of the spark plug, fuel is
reaching the combustion chamber.
If there is
no
fuel at the tip of the spark plug, check
for fuel flow from the fuel tank (Test 3).
3. Check for fuel flow from the tank to the fuel pump.
a. Remove the fuel line from the inlet fitting of
the fuel pump.
b. Hold the line below the bottom of the tank.
Open the shut-off valve (if so equipped) and
observe flow.
3. If fuel
does
flow from the line, check for faulty
fuel pump (Test 4).
If fuel
does not
flow from the line, check the fuel
tank cap vent, fuel pickup screen, in-line filter,
shut-off valve, and fuel line. Correct any
observed problem and reconnect the line.
4. Check the operation of the fuel pump.
a. Remove the fuel line from the inlet fitting of
the carburetor.
b. Crank the engine several times and observe
flow.
4. If fuel
does
flow from the line, check for faulty
carburetor. (Refer to the Carburetor portions of
this section.)
If fuel
does not
flow from the line, check for a
clogged fuel line. If the fuel line is unobstructed,
check for overfilled crankcase and/or oil in pulse
line. If none of the checks reveal the cause of the
problem, replace the pump.
Fuel Pump
General
These engines use either a mechanical fuel pump, or
optional remote-mounted electric fuel pump
assembly. See Figures 5-1 and 5-2. Operation of the
mechanical fuel pump occurs by direct lever/pump
actuation off rocker arm movement. The pumping
action causes the diaphragm on the inside of the
pump to pull fuel in on its downward stroke and to
push it into the carburetor on its upward stroke,
internal check valves prevent fuel from going
backward through the pump.
Troubleshooting – Fuel System Related Causes
Figure 5-1. Mechanical Fuel Pump.
Fuel
Pump
