1965 FIAT 500 diagram

After the crankshaft has been reground it is important
that all traces of swarf are removed by constant washing
and then drying with a non-fluffy rag.
The clearance between the main bearings and journals
must be checked before installing the crankshaft in the
engine. It should also serve as a recheck after the
crankshaft has been reground.
Measure the maximum main bearing internal
diameter and the minimum journal diameter using
accurate measuring equipment. The clearance must not
exceed .0039 inch otherwise the journals must be
reground and undersize bearings fitted.
Undersize bearings w i t h .0394 inch stock on the
internal diameter are also supplied unmounted. They
must be press fitted in the supports, the recommended
interference fit being .00039 to .00197 inch. After
pressing the bearing into the support, a hole is drilled in
the bearing in line with the location dowel hole in the
support. The hole is finished with a suitable expanding
reamer, such as Fiat U.0334, and the dowel pressed i n ,
noting that the hollow dowel fits in the flywheel end
support.
The next stage is to heat the assembly in an oven or
oil bath for a period of one hour at 150°C (302°F).
When the assembly has cooled to room temperature,
the bearing is reamed in a lathe to match the crankshaft
journal size.
3
Crankshaft oil seals:
Two inner spring rubber oil seals are located, one in a
special seat in the timing gear cover and the other in the
flywheel end of the crankshaft support and provide oil
tightness. These seals are shown in FIGS 1 :3 and 1 :34.
Whenever the engine is dismantled for overhaul these
seals should be carefully inspected for correct seating and
that the inner seal surface is not worn and that the contact
area is perfect both on the crankshaft and on the fan and
generator drive pulley hub.
Clutch shaft pilot bushing:
A self-lubricating bronze bush is fitted in the end of the
crankshaft as shown in FIG 1 :34 and provides a bearing
for the clutch shaft. Should the bush be worn use Fiat
puller A.40006/1 /2 to remove the worn bush. A new bush
should be fitted using a suitably sized drift.
1:12 Flywheel and starter ring gear
The flywheel should be inspected for wear at the clutch
driven plate contact area. It should be flat and have a
smooth finish.
The ring gear teeth should be cheeked for damage
which if evident, the ring gear must be replaced. To facili-
tate the fitting of a new ring gear on the flywheel, the new
ring gear should be heated in an oil bath to a temperature
of 80°C (176°F). Using a press gently ease the
expanded
ring gear over the flywheel and press fully home.
1:13 The oil pump
Sedan :
A helical-spur gear type oil pump is driven by the cam-
shaft through a front dog drive coupling. The gears are
F50025 To remove the pump from the engine proceed as
follows:Pump removal and reassembly:
Remove the engine rear central support from the timing
gear casing. Remove the filter cover pulley and lift
away the drive belt.
Release the hollow screw attaching the slinger and the
mounting flange of the filter on the crankshaft. Also
release the nuts fixing the timing gear cover to the
crankcase.
Remove the timing gear cover together with the oil
pump assembly and the pressure relief valve.
Lift out the oil pump suction scoop with the filter
screen attached from the sump.
Reassembly of the pump to the engine is the reverse
procedure to dismantling. 1
2
3
4
5 located in a special housing in the timing gear cover and
held in place by a cover plate. The oil pressure relief valve
is mounted on the drive gear shaft guide.
A pump suction scoop fitted with a filter screen is
secured in the crankcase and connects to a duct in the
timing gear case as s h o w n in FIG 1 :36.
2
4
6Key t o Fig 1 :36
Rocker shaft
Ducts, cylinder head oil drain
Oil pressure relief valve
to centrifugal filter
9
with central oil gallery
12Sump cooling air conveyor
indicator sending unitOil filler with vent valve
Line, oil delivery to rocker shaft
Level indicator rod 31
5
7Gear pump
8 Oil duct
Centrifugal oil fitter
1110
Crankshaft
Oil pump intake screen filter
13 Low oil pressure FIG 1:36 Engine lubrication diagram

FIG 1:37 Lubrication diagram of engine 120.000
Key to Fig 1:37 1 Oil dipstick 2 Oil filler with vent valve 3 Centrifugal oil filter
4 Crankshaft, with central oil gallery 5 Low oil pressure indicator sending unit 6 Oil pressure relief valve 7 Gear pump
8 Camshaft, with central oil gallery 9 Oil suction filter from sump 10 Oil sump drain plug
11 Oil delivery line to rocker shaft 12 Rocker shaft 13 Head cover
Pump dismantling, inspection and reassembly:
Remove the lock ring and withdraw the pressure relief
valve and spring. Remove the oil pump cover plate and
ease o u t t h e gears and shaft.
Thoroughly clean all the parts and blow clean using a
compressed air jet. Inspect the timing gear cover for
cracks or distortion. Check that the inner duct for oil
delivery to the pump is clear of obstruction. Use a
compressed air jet to clean the passage.
Check the oil pump gear teeth for damage or excessive
wear and fit new gears if necessary. The recommended
backlash is .0059 inch w i t h a maximum wear limit
giving a backlash of .0079 inch. Check the clearance
between the gear teeth and the housing walls in the
timing gear cover. The recommended clearance is .0012
to .0035 inch w i t h a maximum of .0047 inch. Ensure
that the drive gear is firmly attached to its shaft. Upon
assembly there is a pinch fit of .0016 to .0031 inch
between the t w o parts.
The driven gear to shaft clearance upon assembly is
.00079 to .00236 inch with a maximum wear limit of
.0039 inch. Also check the width of the drive and driven
gears which when new should be .3937 to .3928 inch
with a minimum width of .3917. In service a spare drive
gear is supplied complete with its shaft.
26 4 3 2 1
Station wagon:
A helical-spur gear type oil pump is driven from the
lower end of the distributor drive spindle which is in mesh
w i t h the camshaft. The gears are located in a special
housing in the bottom of the timing gear housing and are
held in place by a cover plate. The oil pressure relief valve
is located at the driven end of the camshaft.
A pump suction oil filter is fitted in the sump and this
connects to a duct in the timing gear case so supplying oil
to the pump (see FIG 1 : 3 7 ) .
Pump gears removal, inspection and reassembly:
To remove the pump gears from the timing gear cover
proceed as follows:Inspect the filter screen on the end of the pump suction
scoop and remove any obstruction. If the screen is
damaged it must be renewed.
Check that the pump drive dog is a good fit on the cam-
shaft and that the dogs are not badly worn so as to
impair the pump operation.
Reassembly of the pump is the reverse procedure to
dismantling. Ensure that the pump cover piate is
correctly located by means of the dowel on the timing
gear cover. 5
6
7

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 : 6 Weber 26.IMB carburetter starting device
(choke) end
Key to Fig 2 : 6 1 Choke device cover 2 Bowden
mounting screw 3 Nut and screw, choke bowden wire
4 Choke control lever A Position of lever 4 for 'fully
inserted' choke B 'Partially inserted' choke
C 'Disinserted' choke
caused by the engine suction and the charge is then drawn
into the cylinders.
The secondary venturi 24 is to increase the vacuum
around the nozzle 25 and to carry the charge to the centre
of the primary venturi 2 1 .
When the engine is idling, fuel is carried from the well
23 via an appropriate passage to the idle speed jet 13
where it is mixed with the air coming from the air inlet 5.
Through duct 3 and idle speed orifice 18 (adjustable by
means of a taper point screw 17), the fuel reaches the
carburetter throat, past throttle butterfly 19 where it is
further mixed with the air stream drawn in by the engine
vacuum through the gap around the throttle in the idling
speed position.
From the d u c t 3 the mixture can also reach the car-
buretter throttle chamber through a transition hole 20
which is located in exact relation to the throttle butterfly.
The purpose of this progression hole is to permit a smooth
acceleration of the engine from the idling speed, this being
proportional to the increase in the throttle opening.
Starting device:
This enables the engine to be started when it is cold
under the most arduous of weather conditions. It is con-
trolled by means of a lever placed behind the gearshift
lever and must be progressively adjusted to its normal
rest
position as the engine reaches the normal operating tem-
perature. The starting device comprises a valve 33 (see
FIG 2 : 5) actuated by the lug of the rocker 36 which is
connected to the control lever 38 by a suitable shaft. By
38
pulling the device control fully across through lever 38
and rocker 36, the valve 33 is lifted from its seating and
brought into the 'fully open' position. Refer to diagram 'A'
(FIG 2 : 5) . Under these conditions the valve 33 closes
the air hole 27 and the mixture hole 29 and uncovers
mixture orifices 30 and 32 which also communicate with
the starting jet 46 through a duct 26 and air holes 35.
With the valve 33 partially open the hole 29 may com-
municate with the carburetter throat through the valve
central slot, duct 28 and the hole 31 drilled in the venturi
21 corresponding with the venturi restriction.
When the throttle is set at the idling speed position, the
engine vacuum caused by the operation of the starter
enables the fuel contained in the recess of jet 4 6 , in the jet
and in the reserve well 45 to be mixed w i t h the air coming
from holes 43 and 44. The mixture arrives through the duct
26 and holes 30 and 32, at the same time as air passing
from the holes 35, past the throttle through duct 34 so
permitting easy starting of the engine.
After the engine has fired initially, the device will deliver
a charge with a rich petrol/air ratio so as to permit regular
running of the engine whilst it is cold. As soon as the
engine has warmed up to normal operating temperature
this charge would obviously be too rich and therefore it is
necessary to gradually ease o f f the operation of the starting
device as the engine reaches its normal operating tempera-
ture. During this adjustment the valve 43 slowly uncovers
the hole 27 which will permit a greater amount of air to
enter through the spring guide hole 42 so weakening the
mixture at the same time as closing the progression holes
30 and 32 and air holes 35 the amount of mixture is also
reduced. See diagram ' B ' (FIG 2 : 5).
The hole 29, the duct 28 and the hole 3 1 , which are
drilled in the venturi 21 permit a regular progression of
acceleration whilst the engine is cold as well as when it is
at normal operating temperature. By opening the throttle
butterfly 19 to increase the speed of the engine the
vacuum acting on the duct 34 is decreased. This causes a
drop in the amount of fuel delivered through duct 34 with
consequent irregular running of the engine but, through
hole 3 1 , duct 28 and hole 29 some charge is sucked in by
the vacuum formed in the restriction of the venturi, caused
by the opening of the throttle and this automatically com-
pensates for the reduction in the delivery through the duct
34.
When the starting device is not in operation, valve 33
covers the hole 29 and so preventing the passing of fresh
charge. Diagram ' C (FIG 2:5).
Engine s t a rting:
So that full advantage may be taken of the progressive
action starting device the engine should be started as
follows:
1 Cold starts:
The starting device should be moved across the position
'A', (FIG 2 : 6) . Once the engine has fired push the control
in partially.
2 Warm starts:
Only partially move the starting device as shown in
position 'B' (FIG 2 : 6).

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)

3938
28 29 30A3132 33
28 29 30 3.1B28
29 30 31C
34 34
34
37 36 35 23
FIG 2:13 Diagrammatic section views of 26.OC Weber carburetter through the starting device
1
2.34
5
27
26.
25,
24.
23.
22
1617
8
21
209
_6
.4
7
.8
10 19 1817
16 1595
1011
1213
14.
FIG 2 :14 Diagrammatic section views of 26.OC Weber carburetter
Key to Fig 2:14 1 Fuel inlet connection 2 Filter gauze 3 Filter inspection plug 4 Air corrector jet
5 Air intake 6 Idle speed jet holder 7 Idle airduct 8 Emulsion tube 9 Secondary venturi 10 Idle mixture duct
11 Primary venturi 12 Progression hole 13 Idle orifice to duct 14 Idle mixture adjustment screw 15 Throttle
16 B o w l - t o - w e l l duct 17 Emulsion tube housing well 18 Well-to-idle jet duct 19 Idle speed jet 20 Nozzle
21 Emulsion orifices 22 Main jet 23 Bowl 24 Float 25 Float pivot 26 Valve needle 27 Needle valve
When the starting device is not in operation valve 30
covers the hole 29 so preventing the passage of mixture as
shown in diagram 'C (FIG 2:13).
Engine starting:
So that full advantage may be taken of the progressive
action starting device the engine should be started as
follows:
1 Cold starts. The starting device should be moved
across to position 'A' as shown in FIG 2:13. Once the
engine has fired push the control in partially.
42
2 Warm starts. Only partially move the starting device
to position ' B ' as shown in FIG 2:13.
3 Engine warm-up. As the engine begins to warm up to
its normal operating temperature. Gradually push home
the starting device lever so as only to supply the engine
with the richened charge enabling the cold engine.
operation to be smooth and regular. Position ' B ' s h o w n
in FIG 2:13.
4 Normal car driving. Once the engine has reached its
normal operating temperature the starting device
should be completely brought out of operation by
bringing the control lever to the position C shown in
FIG 2:13. Key t o Fig 2 : 1 3
23 Bowl 28 Starting mixture duct
29 Starting mixture duct30 Starting valve
34 Emulsion air orifices
38 Starting air corrector screw
C Choke disengaged B Choke partially inserted 37 Starting jet33 Bowden fixing screw
A Choke fully inserted 36 Starting reserve well 32 Starting device control wire 31 Starting device control lever
35 Bowl-to-starting jet duct
39 Reserve well emulsion air slot

1
14,5
7,52 9 48 35
76
FIG 2:15 Float level setting diagram Weber car-
buretter type 26.OC
7.5 = .29 inch 14.5 = .57 inch
Key to Fig 2:15 1 Carburetter cover 2 Cover gasket
3 Needle valve 4 Valve needle 5 Lug 6, 7 Arms
8 Needle ball 9 Float
Idle speed adjustment:
The idling speed is adjusted by movement of the throttle
setscrew and the mixture setscrew. The throttle screw
allows for the adjustment of the throttle opening whereas
the conical mixture setscrew has the purpose of metering
the amount of charge issuing from the idling speed pas-
sage, which will then mix with the air flowing past the
throttle which when correctly set for normal idling speed
should leave a gap between its edges and the throat walls.
This ensures a correct petrol/air ratio best suited to the
engine requirements and smooth operation.
The idling speed should always be adjusted with the
engine running and at its normal operating temperature
by first setting the throttle to its minimum opening by
turning the throttle setscrew so enabling an accurate
adjustment to be made. Then slowly turn the mixture set-
screw either in or out so as to adjust the mixture petrol/air
ratio to the most suitable for the throttle opening, this will
accomplish a fast and steady idling speed which should be
then reduced by closing the throttle opening slightly by
easing back the throttle setscrew. This adjustment should
continue until the best idling speed is obtained.
Adjustment of fuel level in float chamber:
To check and adjust the level of fuel in the carburetter
float chamber proceed as follows:
1 Check that the needle valve 3 (see FIG 2:15) is
screwed tight on its seat.
2 Keep the carburetter cover 1 upright or else the weight
of the float 9 will lower the ball 8 fitted on the needle 4.
F50043
Key to Fig 2:17 1 Filter housing 2 Spring hooks
3 Filter element 4 Cover 5 Air suction pipe, hoses
and clamps 6 Re-circulation pipe for blow-by gases and
oil vapoursFIG 2:17 Removing the air cleaner, 500F, L
2
1 3
4.
6
5
FIG 2:16 Taking out the filter element, 500, 500D AIR CLEANER ELBOW
HOSE
AIR CLEANER BODY
FILTER ELEMENT Check that with the cover held in the vertical position
and the float arm 6 in slight contact with the ball 8 of the
needle 4, the float is .2953 inch away from the cover
w i t h its gasket 2 fitted flat against the cover face.
3 Check that the float level is .5709 inch from the cover
face and if necessary bend the lug 5 to give the required
setting.
4 If the float 9 is not correctly positioned bend the float
arm 7 until the correct adjustment is obtained. Ensure
that the arm 6 is perpendicular to the needle axis and
does not show any rough spots or indentations which
might impair free movement of the needle. Check that
the float 9 moves about its pivot pin.
Every time a new float or needle valve is fitted the above
detailed adjustment operations must be completed to
ensure correct fuel levels.

FIG 2:18Diagram of blow-by gases re-circulation device
Key to Fig 2:181 Head cover 2 Blow-by gases and oil vapours breather valve 3 Oil filler cap4 Strainer
9 Air suction pipe, air cleaner to carburetter 8 Flame trap
13 Exhaust duct 12 Crankcase 7 Carburetter 6 Air cleaner
11 Filter gauze
10 Movable partition 5 PipeEngine 110 F. 000 Engine 120.000
designed to dampen the air intake noise and the carburet-
ter venturi hiss and is so located in the blower conveyor
system so that only clean dry air is drawn into the induc-
tion system.
To ensure complete protection of the engine it is
recommended that the air filter element be replaced every
6000 miles or even earlier if the vehicle is operating in
dusty conditions.
It should be noted that an oversize air cleaner may be
obtained if the vehicle is to be operated in very dusty areas.
Air cleaner—engine 110 F.000:
To remove the air cleaner element, disengage both the
spring hooks 2 as shown in FIG 2:17 and lift away the
cover 4 by turning it inwards together with the hose 5. 2 : 9 Air cleaner (sedan)
The pleated paper air cleaner element is contained in a
casing housed in a recess of one of the silencing chambers
provided in the blower conveyor as shown in FIG 2:16.
The air cleaner is connected to the carburetter by means of
a specially shaped hose. The silencing chamber is
44For full instruction refer to Section 2 :6. Carburetter cleaning:See Section 2 :6 for full check details. Throttle valve components:
Engine 110 F. 000