Pulsating-Diaphragm Fuel Pump - Onan T260G Service Manual

Reassembly and Installation (Walbro)
1. Install needle valve and seat, main jet and fioat
assembly. Make sure that float pivot pin is properly
placed and that float moves freely without binding.
2. Gently push float tang down until needle just seats.
(Figure 4). Measure float level; adjust if necessary.
Release float tang and measure float drop; adjust if
necessary. When checking float level and drop,
measure to float body, not seam.
3. Position gasket on carburetor and attach carburetor
sections together with screws.
4. Slide in throttle shaft and install plate using new
screws. Before tightening the screws, the plate must
be centered in the bore. To do so, back off the
throttle stop screw as necessary and completely
close the throttle lever. Seat the plate by tapping
with a small screwdriver, then tighten screws. Install
the choke shaft and plate in the same manner.
5. Install idle adjustment screw, throttle stop screw,
and main fuel adjustment needle.
6. Mount carburetor on intake manifold and install
assembly on engine.
7. Mount air cleaner assembly. Connect air intake
hose, breather hose, fuel line, vacuum line, and
throttle linkage.
8. Adjust carburetor and governor according to direc-
tions given in this section.
Reassembly and Installation
(Nikki limited idle adjustment)
1.
Install needle valve, main jet, and float assembly.
Make sure float pivot pin is properly placed and f l o a /
moves freely without binding.
2. Turn carburetor on its side and measure float level
(Figure
4).
Adjust float level only if necessary.
Measure float drop (the distance from the top of
carburetor body to top of float). Adjust only if
necessary.
3. Position gasket on lower carburetor section and
install upper carburetor section.
4. Install idle adjustment screw, throttle stop screw,
and fixed main jet plug.
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5. Mount' carburetor on intake manifold and install
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assembly on engine.
6. Mount' air cleaner assembly. Connect air intake
hose, breather hose, fuel line, vacuum line, and
throttle linkage.
7. Adjust carburetor and governor according to direc-
tions given in this section.
ASSEMBLY
SCREWS
VALVE DIAPHRAGM
REED VALVE
FIGURE 5. EXPLODED VIEW OF FACET FUEL PUMP
PULSATING-DIAPHRAGM FUEL PUMP
Pulsating-diaphragm fuel pumps, or pulse pumps, rely
on changes in crankcase vacuum to create a pulsating
movement of the pump diaphragm. As the engine's
pistons move outward, a vacuum is created. This
vacuum is transmitted to the pump diaphragm, causing
it to pull back and suck fuel into the pump. As the
engine's pistons move inward, crankcase vacuum is
reduced and the diaphragm return spring pushes the
pump diaphragm forward, forcing fuel through the
pump outlet.
PUMP BASE
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Fuel Pump Test Procedure
Before testing make certain that fuel pump vacuum line
connections are tight and free of leaks.
1.
Operate engine at an idle for five minutes to ensure
2. Shut engine off and remove fuel inlet line from fuel
that carburetor is full of fuel.
pump.
WARNI N G
WARNING
Spilled fuel can ignite and cause
serious personal injury or death.
Thoroughly clean-up any spilled fuel.