Fiat 500F - CHAPTER 2 THE FUEL SYSTEM; 2:1 Description; 2:2 Fuel pump operating principles; 2:3 Routine maintenance

CHAPTER 2
THE FUEL SYSTEM
2:1 Description
2:2 Fuel pump operating principles
2:3 Routine maintenance
2:4 Pump removal, dismantling and examination
2:5 Reassembly, installation and adjustment
2:6 Carburetter operation and adjustment,
Weber 26.1MB
2:7 Modifications
2:8 Carburetter operation and adjustment,
Weber 26.OC
2 :9 Air cleaner
2:10 Blow-by gases recirculation device
2:11 Fuel tank
2:12 Fault diagnosis
2:1 Description
All the new 500 models use a mechanical diaphragm
fuel feed pump as shown in FIG 2:1. Four types of
carburetter are fitted depending on the model to which
the engine is installed. Each carburetter operation and
adjustment is fully described, together with details of the
recirculation device for blow-by gases and oil vapours.
2:2 Fuel pump operating principles
Refer to FIG 2 :2. An eccentric on the rotating camshaft
actuates the operating rocker 21 via a pushrod 25 which
depresses the diaphragm 14 and so creates a depression
in the pumping chamber located in upper body 5. Under
atmospheric pressure, petrol passes through the pipeline
connection and inlet valve into the pumping chamber.
The return spring 15 then raises the diaphragm, expelling
the petrol through the outlet valve and pipeline to the
carburetter float chamber.
When the float chamber is full, the pressure in the pipe-
line and pumping chamber holds the diaphragm depressed
against the tension of the return spring.
2:3 Routine maintenance
A poor delivery of fuel to the carburetter may be due to
a fault in the fuel pump or related lines. Periodically the
pump body screws 19 (see FIG 2:2) and upper cover
screw 1 should be checked for tightness. The fuel pump
lines should be disconnected and checked for freedom of
restriction, chafing and loose connections. The fuel pump
filter should be removed and cleaned periodically.
2:4 Pump removal, dismantling and examination
The pump is located on the carburetter side of the
engine crankcase (sedan) or under the generator at the
front of the crankcase (station wagon).
Removal:
1 Disconnect the fuel pipe from the tank to stop petrol
syphoning out of the tank and then release the fuel
inlet and outlet pipes from the pump body.
2 Remove the two nuts and washers holding pump to
crankcase.
3 Carefully lift away the pump, gaskets and insulating pad
from the crankcase (see FIG 2:3).
F500
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