Page No: 55
Issue No: 1
Date: 031100
Issued By: PJA
Jabiru 3300 Component Inspection and Assembly
7.4.7
Sub-Assembly G - Fuel Pump and Carburettor and Carburettor Operation
Fuel Pump
The fuel pump on the 3300 engine is replaced as a complete unit at overhaul. It can be
inspected for faults by removing the top half.
Things to look for are:
1) Stuck or leaking valves
2) Torn diaphragm
3) Weak springs
4) Broken actuating lever.
Carburettor Operation
The BING constant depression carburettor type comprises a cross draught butterfly-valve
carburettor with variable choke tube, double-float system arranged centrally below the
carburettor venturi and a rotary-valve type starting carburettor. It features a throttle slide
which is suspended from a roller diaphragm and projects into the venturi. It changes the
smallest cross-section ("choke tube") of the venturi as a function of the vacuum at this
point.
MOUNTING
The carburettor is secured to the engine using a push-on connection which takes a flexible
connecting piece with clamps. On the intake side the carburettor is provided with a
socket having a diameter of 50mm and a length of 12mm for connecting an air filter or
intake silencer.
FUEL INTAKE CONTROL
The float (40) of the carburettor consists of two plastic float elements joined by a metal
hinge. The float is arranged centrally below the carburettor choke tube so that the
carburettor can be tilted very far in all directions without impairing operation. The object
of the float is to maintain the fuel level in the float chamber (44) constant. When the fuel
has reached a specified level in the float chamber, then the float (40) mounted on pin (41)
is lifted until the float needle (42) is pressed against the seat of the float needle valve, thus
preventing any further supply of fuel. When the engine draws in fuel from the
carburettor, the level in the float chamber (44) drops and so does the float. The float
needle then opens the valve again and allows fuel to flow in from the tank. The float
needle valve regulates the fuel supply in conjunction with the float but it does not act as a
stop valve when the engine is at a standstill. Minute foreign bodies may be deposited
between valve seat and needle tip, thus preventing complete closure of the valve. When
stopping the engine, therefore, the fuel cock on the tank should always be closed. In
addition the fuel should be filtered before it reaches the carburettor. The filter should be
Summary of Contents for 3300
Page 4: ...Page No 4 Issue No 1 Date 031100 Issued By PJA List of Amendments Page Amendment Date Issue...
Page 8: ...Page No 8 Issue No 1 Date 031100 Issued By PJA 1 1 Denomination of Cylinders...
Page 11: ...Page No 11 Issue No 1 Date 031100 Issued By PJA 3 0 PERFORMANCE GRAPHS...
Page 48: ...Page No 48 Issue No 1 Date 031100 Issued By PJA...
Page 52: ...Page No 52 Issue No 1 Date 031100 Issued By PJA...
Page 67: ...Page No 67 Issue No 1 Date 031100 Issued By PJA Drawing 9430064...
Page 89: ...Page No 89 Issue No 2 Date 031100 Issued By PJA...