1959 FIAT 500 driver seat adjustment

FIG 2:5 Starting device (choke) diagrammatic section
KeytoFig2:5 A Device fully inserted B Device partially inserted C Device disinserted 2 Air inlet 16 Bowl
19 Throttle 21 Primary venturi 24 Secondary venturi 26 Mixture duct 27 Mixture leaning air orifice
28 Transition duct 29 Transition mixture orifice 30 Starting mixture orifice 31 Transition orifice
32 Starting mixture orifice 33 Starting valve 34 Mixture duct 35 Starting device air orifices 36 Rocker
37 Lever return spring 38 Starting device control lever 39 Control wire screw 40 Cover with support for starting
device control bowden 41 Starting valve spring 42 Spring casing. 43 Starting jet emulsion air orifice
44 Air emulsion reserve well orifice 45 Starting reserve well 46 Starting jet
F50037
FIG 2 : 4 Diagrammatic section of Weber 26.IMB
carburetter
KeytoFig2:4 1 Air corrector jet 2 Air inlet
3 Idle speed mixture duct 4 Idle speed jet holder
5 Idle speed air orifice 6 Filter cover 7 Filter
8 Fuel inlet connection 9 Needle valve seat 10 Needle
11 Float pivot 12 Float 13 Idle speed jet
14 Main jet holder 15 Main jet 16 Bowl
17 Idle speed mixture adjustment screw 18 Idle speed
mixture orifice 19 Throttle 20 Transition hole
21 Primary venturi (not interchangeable) 22 Emulsion
orifices 23 Emulsion well 24 Secondary venturi
(not interchangeable) 25 Main nozzle
design with a 1.0236 inch diameter throat measured at the
height of the throttle shaft. The amount of charge passing
to the manifold is controlled by a throttle butterfly valve
from an accelerator pedal operating a lever secured to the
throttle valve shaft via a cable. The carburetter is fitted with
a progressive action starting device which enables the
driver to suit the mixture richness to the most arduous of
starting conditions, and will enable the engine to run
evenly until it reaches its normal operating temperature.
A dampened needle valve ensures a smooth running
engine as it is not affected by engine vibrations and there-
fore giving a constant fuel level in the carburetter bowl. A
secondary venturi is incorporated in the single casting of
the carburetter body and this has a diameter of 0.8268 inch.
Carburetter operation:
Filtered air flows through the venturi 24 (see FIG 2 :4)
where it mixes w i t h fuel flowing from the nozzle 25 and
the charge is then conveyed to the cylinders through the
primary venturi 21 and throat, where the throttle butterfly
19 controls the amount of charge.
Petrol flows from the main fuel line to the bowl 16
through a gauze filter 7 and needle valve 10, where the
float 12 pivoting at point 1 1 , controls the opening of the
needle 10 so maintaining a constant fuel level. From the
bowl 16 fuel reaches the emulsion well 23 via the metered
main jet 15 where, after having been mixed with the air
coming from the metered air corrector screw 1, through
the emulsion orifices 22 and spray nozzle 25, it finally
reaches the Venturis where it mixes w i t h the air stream

FIG 2 : 9 Weber 26.IMB carburetter cover components
Key toFig 2 : 9 1 Float 2 Carburetter cover 3 Float pivot 4 Needle valve gasket 5 , 6 Needle valve seat and needle valve
7 Cover gasket 8 Filter strainer 9 Gasket 10 Filter inspection plug
Carburetter cleaning:
To thoroughly clean the carburetter proceed as follows:
1 Passages. All fuel passages have a diameter that is
specially calibrated to ensure best operating conditions.
It is therefore essential that any dirt or scale that has
been deposited by petrol must be removed. Thoroughly
clean with petrol and blow dry using a compressed air
jet directed through all the passages in the castings. It is
essential that no drills or other metal objects be passed
through the jets or the passages otherwise these could
alter the finely calibrated diameters.
2 Calibrated parts. Idling and main jet holders, and the
relevant bayonet coupled jets are easily removed by
using a suitably sized wrench or screwdriver. To clean
the different calibrated parts, thoroughly wash in petrol
and blow dry using a compressed air jet. Do not use any
fine drills or metallic points as these may alter the fine
calibration of the orifices. Should it be necessary to dis-
mantle the carburetter adjustment components for
inspection always ensure that after reassembly of the
parts that they are seated correctly to avoid possible
operating troubles in the future.
3 Filter. To clean the filter unscrew and remove its plug
10 (see FIG 2 : 9) located on the top of the carburetter
cover and then gently ease o u t t h e filter. Wash the filter
carefully in petrol, also ensure that the filter seat is clean
and then blow dry using a compressed air jet.
2:7 Modifications
The Weber 26.IM B carburetter has undergone a number
of minor changes during the development of the Fiat 500
models, but no changes in servicing procedure are made
necessary. Jet sizes and other calibrations are detailed
in Technical Data.
From 1970, the mounting flange of the carburetter is
slightly modified to incorporate a different mixture
adjustment screw, as shown in FIG 2:11.
40
Throttle valve components:
The throttle valve shaft should rotate freely in its guides
and this should be checked when the engine is at its
normal operating temperature. Any excessive clearance
caused by wear or the throttle valve butterfly distorted are
liable to cause irregular engine operation which will be
more pronounced at idling speed. Should the above con-
ditions be evident then the throttle valve butterfly and the
shaft assembly together with its sealing rings must be
renewed.
FIG 2:10 Jets, jet holders and choke valve
Key to Fig 2:10 1 Choke valve 2 Spring
3 Spring retainer and guide 4 Lock ring 5 Air bleed jet
6 Emulsion well 7 Choke jet 8 Idling jet holder and jet
9 Main jet holder and jet 10 Main jet holder gasket

FIG 2:12 illustrates the starting device fitted to
26.IMB.4 and later carburetters. It differs from earlier
units in detail, principally in having fewer starting mixture
orifices 30 and 32 into the mixture duct 26.
2 : 8 Carburetter operation and adjustment,
Weber 26. OC
The new 500 station wagon is fitted with the Weber
26.OC carburetter which is of a horizontal draft design to
suit the engine which is fitted in the horizontal position.
The carburetter is fitted with a progressive action starting
device which enables the driver to adjust the mixture rich-
ness to the most arduous of starting conditions, and will
enable the engine to run eyenly until it reaches normal
operating temperature.
A dampened needle valve ensures a smooth running
engine as it is not affected by engine vibrations and there-
fore giving a constant fuel level in the carburetter bowls.
A secondary venturi is incorporated in the single casting
of the carburetter body.
Carburetter operation, starting device:
The petrol from bowl 23 (see FIG 2:13) reaches the
starting jet 37 through the duct 35. By operating the choke
lever 31 to the end of its stroke, the valve 30 is lifted from
its seat and brought to the 'fully open' position as shown
in diagram 'A' (FIG 2:13). Under these conditions the
valve 30 uncovers both the starting mixture ducts 28 and
29. With the throttle set in the idling speed position the
engine vacuum created by the operation of the starter
motor causes the fuel contained in the recess of j e t 37 in
the jet and the reserve
well 36 to be mixed with the air
coming from the air jet 38.
The mixture arrives through the ducts 28 and 29 at the
same time as air from holes 34, past the throttle so per-
mitting easy starting of the engine.
A
B
C
FIG 2:12 Section of later starting device
Key to Fig 2:12 A Cold starting position B Warming up position C Normal running position
2 Air inlet 21 Primary venturi 24 Secondary venturi 26 Mixture duct 27 Air bleed 30,32 Starting mixture orifices
33 Valve 34 Mixture duct 35 Air orifices 38 Rocker 39 Lever return spring 40 Control lever 41 Control wire screw
42 Cover and cable support 43 Valve spring 44 Spring guide and retainer 45 Starting jet emulsion air duct 46 Emulsion
air reserve well duct 47 Reserve well 48 Starting jet
F50041 Once the engine has initially fired the starting device will
deliver a mixture whose petrol/air ratio is such that the
engine will run regularly even though it is cold. As soon as
the engine warms up this rich charge would be excessive
and therefore it becomes necessary to gradually ease back
the operation of the starting device. As this is occurring,
the valve 30 gradually covers up the mixture duct orifice 28
so as to weaken the mixture while by closing the duct 29
gradually. It also reduces the amount of mixture delivered
by the carburetter as shown in diagram ' B ' (FIG 2:13). FIG 2:11 Mounting flange modification: A earlier, B
later (dimensions in mm)

Inner panels:
Imitation leather-lined masonite trim panels are fitted
to all versions of the new 500' models. The panels are
secured in the housing below the door window by means
of four stiff clips located at the top and seven spring clips
located at the bottom equally spaced around the panel
border. The fasteners are located in holes in the door
framework inner flange. The door framework has a plate
which should be bent downwards onto the trim panel
once it has been installed. This will ensure correct seating
of the trim panel in the door housing.
When the door trim panel is being reassembled ensure
that the tarred felt pad is cemented correctly on the door
inner flange so that any water that may seep in through to
the door interior from the window rubber weather strips
may be kept away from the trim panel which would
otherwise cause distortion and rapid deterioration.
12:4 Door handles and locks
The doors are provided with locks which are operated
by handles either from inside or outside the vehicle.
Removal of the lock is a straightforward operation but
upon reassembly the following procedure should be
followed:
1 Mount the handle assembly from the outside and
insert the washer onto the stud. Screw in the nut several
turns to allow correct handle-to-lock mating on final
fitting.
2 Arrange the locking handle dog so that it is horizontally
positioned and tighten the mounting nut.
3 Mount the lock to the door panel and secure w i t h three
screws and washers.
4 Fit the plate w i t h the t w o rubber guide blocks fastening
by the t w o screws.
Striker plates are fitted with shim adjustment to the
door pillars and are secured by three screws.
12:5 Removing window regulator and door glass
Window regulator:
Description:
The window regulator unit is of the lever and gear
control type which transmits crank movement to the
lifting lever using high ratio gears. When the operating
handle is rotated it rotates a pinion mounted on its shaft
which is in mesh w i t h a gear on the hub of which is
mounted a second pinion that meshes with the lever
toothed sector (refer to FIG 1 2 : 3) . At the end of the lever
a pin fitting locates in a guide rail mounted on the
bottom of the glass. When the crank is rotated in one or
other direction the glass is either lifted or lowered.
Regulator removal:
1 Depress the door lining panel so that the crank key may
be located. Remove the key and the crank handle.
2 Using a wide blade screwdriver prise off the trim panel
by inserting the blade between the panel and the door
frame taking care not to scratch the door paint.
3 Remove the intermediate protection lining.
F500129
FIG 12:3 Lefthand side door window regulator, viewed
from car interior
FIG 12:4 Location of window regulator in lefthand side
door panel housing
4 Release the screws securing the window regulator
to the door. Carefully tilt the regulator so as to dis-
engage the lever pin from the guide on the bottom of
the glass and lift away the regulator assembly.
Regulator reassembly:
To ensure satisfactory regulator operation carefully
lubricate the gears and the lever pin guide and also
ensure that the glass slides freely in its channels. To

cushion and back rest. A number of rubber straps are
hooked across the frame under the cushion and in a
sheath covering on the seat back.
The bottom of the front seat frame ends are provided
with sliding guides which run in guide rails attached to
the floor. The sliding guides are pivoted on the frame
tubes to allow for forward tilting of the seats giving better
access to the rear compartment. Two rubber pads
provide cushioning of the seat frame on the guide rails
as shown in FIG 12:11. The control lever for seat
adjustment is fitted in the frame righthand tube to permit
unlocking of the seats so that they may be adjusted to
individual drivers requirements.
Rear seats (Sedan):
The rear seat comprises of a foam rubber cushion and
back. The seat back is cemented to the rear floor and
body shell bulkhead. The rear seat lining is of fabric and
imitation leather. The seat lining is held in place by four
self-tapping screws, t w o of which secure the floor below
the back window and two the lining at the base of t h e
back rest. Included with the seat assembly is a masonite
floor which is fitted below the rear window.
Rear Seat (Station Wagon):
The rear seat back rest is pivoted at the base of its
frame so that it can be folded down to form a load plat-
form surface. In the upright position it is retained in place
by t w o brackets mounted on either side of the body below
the side
windows.
12:14 Interior heater
Description:
Interior heating is accomplished by recirculation of
warm air from the engine cooling system through engine
cowling. Referring to FIG 12:18 a hose conveys warmed
air from the engine cowling to the centre tunnel floor
where warm air flows out through two slots being cut on
the windshield delivery hoses. Air admission can be
adjusted by turning the control lever to the right which
operates the tunnel throttle valve at the rear seat.
The heating system may be fitted with a booster which
comprises a casing on the front exhaust pipe being
connected to the engine cowling and the warmed air
passage tunnel. Warm air flowing to the car interior is
heated to higher temperature than that from the standard
version of heater (see FIG 12:19).
Windshield demisting:
As will be seen from FIG 12:18, t w o air hoses w i t h
throttle valves for airflow control are relayed from a casing
F500135
FIG 12:19 Diagram of booster
Key to Fig 12:19 1 Thermostat controlling shutter
2 Car interior heater booster 3 Hand control unit
in front of the centre of the floor tunnel. Flexible hoses
are connected to two air diffusers which are located on
the instrument panel and parallel to the windshield glass.
When the throttle valves 5 (see FIG 12:18) are operated
through the two control knobs, warmed air is directed
onto the windshield glass so preventing misting, frosting
or icing in adverse weather conditions.
Inspection:
Ensure that t h e lever, the lever spring and butterfly
valve hinge are not distorted. Check that the ducting to
the tunnel as well as the upper and lower hoses are air-
tight which if not, should be renewed.