fuel pump FIAT 500 1971 1.G Workshop Manual

FIG 1:1 Left side view of the power plant to suit
500 Sedan
10
FIG 1:2 Right side rear three-quarter view of the power plant for 500 Station Wagon Mounted on the top of the cylinder head is the overhead
valve rocker mechanism that is operated by a chain driven
camshaft through tappets and vertical pushrods.
The carburetter is of the downdraft type fitted with a
starting device that is controlled by a lever on the central
floor tunnel. A pleated paper element air cleaner and
silencer is fitted to the carburetter air intake. A mechanical
diaphragm type fuel pump operated from the camshaft by
a pushrod, supplies petrol to the carburetter from a fuel
tank located at the front of the vehicle.
Engine lubrication is provided by a gear pump driven
from the camshaft and mounted within the timing cover
drawing oil from the engine sump. The oil is cleaned by a
centrifugal filter situated at the rear end of t h e crankshaft
and pressure is controlled by a valve mounted on the
pump body. Crankcase ventilation is provided for through
a rubber hose connected to the top of the rocker cover.
The engine is cooled by air from a centrifugal blower
mounted on the generator shaft and housed in a specially
designed cowling conveying air to and around the engine.
The air temperature is governed by a special thermostat
fitted in the engine cowling.

6 Release the ignition distributor support retaining nut
and lift away the distributor together w i t h its support.
7 Remove all the mounting bolts of the engine cooling
cowling and lift away the assembly. Release the t w o
carburetter retaining nuts and carefully remove the
carburetter together with its drip tray.
8 Lift away the valve rocker assembly having first
released the t w o retaining nuts together with the plain
washers and lock washers. Carefully lift out the valve
rocker pushrods noting their relevant positions.
9 Slacken the four central cylinder head cap nuts and
the four conventional nuts in the order, shown in
FIG 1 :44 or 1 :46. Lift the cylinder head from the
barrels. If difficulty is experienced it is essential to use
Fiat tool A.40014 or a similar drilled plate, otherwise
serious damage could be caused if other means are
used (see FIG 1:9).
10 Remove the four pushrod sleeves and the casing
containing the oil ducting to the overhead valve gear.
11 Remove the fuel pump retaining nuts and washers
and lift away the pump. Carefully pull out the pump
control pushrod from the crankcase.
12 Remove the six screws holding the centrifugal oil filter
pulley cover and lift away the cover. Remove the
centrifugal filter mounting flange by unscrewing the
crankshaft central bolt. Also remove the timing cover
containing the oil pump gears and the oil pressure
regulating valve. Note the position of the nuts,
toothed and plain
washers for correct reassembly.
13 Release t h e four camshaft sprocket retaining bolts and
lift away the sprocket and timing chain. Using Fiat
pulley A.46020 or a large universal two-leg puller as
shown in FIG 1 :10 remove the crankshaft sprocket
and its body.
14 Carefully lift out the rocker pushrod tappets making a
note of their location and gently pull out the camshaft
making sure the front bearing bore is not damaged by
the cam lobes or distributor drive gear.
15 Mark the flywheel and crankshaft to ensure correct
reassembly and release the six f l y w h e e l retaining bolts
together w i t h the lockwashers and lift away the fly-
wheel.
16 Using Fiat tool A.60156 on the two central studs, lock
the two cylinder barrels in place as shown in FIG 1 : 1 1.
TOOL A. 40014
FIG 1:9 Tool A.40014 for cylinder head removal
F50015
17 Turn the engine upside down ensuring that no weight
is placed on the studs and remove the oil sump and the
oil suction scoop.
18 Mark the connecting rods and end caps to ensure
correct reassembly and remove the end caps. Place the
engine on its side and remove the cylinder barrels
clamp. Ensure that the studs are clean and carefully
slide off the connecting rod-piston-cylinder assem-
blies from the crankcase.
19 Remove the six screws holding the rear main bearing
housing to the crankcase and lift away the housing.
Remove the six screws holding the front main bearing
housing to the crankcase and lift away the housing.
20 Carefully ease the crankshaft from the crankcase
moving it diagonally to assist withdrawal. FIG 1:11 Cylinder hold-down tool A.601 56 TOOL A.60156 FIG 1 :10 Removing crankshaft sprocket w i t h puller
A.46020
PULLER A.46020

STUD REMOVAL
PULLER 40010
FIG 1 :12 Removal of stud from crankcase by puller
A.40010
FIG 1 :13 Engine without blower cowling and cylinder
head cover.SPACER A N D CONNECTION
FOR ROCKER SHAFT
LUBRICATION TUBE
OILVAPOR
.VENT PIPE
CASINGS FOR PUSHRODS
(AND OIL RETURN
TO CRANKCASE
21 To ensure no damage occurs to the long cylinder
barrel mounting studs these may be removed using
Fiat puller A.40010 or a universal stud removal as
shown in FIG 1 :12.
1 :5 Engine disassembly (station wagon)
To dismantle the engine proceed as follows:
1 Remove the exhaust silencer and manifold by releasing
the four nuts holding the two flanges from the cylinder
head. Also disconnect the two silencer mounting
brackets and lift away the exhaust system (see
FIG 1 : 2).
2 Place the engine on a firm wooden top bench. Release
the clip holding the tappet cover and lift away together
with the drip tray. Disconnect the fuel line and throttle
linkage at the carburetter and carefully lift away the
carburetter together with its insulator joint and gaskets.
3 Remove the generator drive belt by releasing the three
nuts so splitting the semi-pulley. Lift away the drive
belt.
16
FIG 1 :14 Tool A.60084 for valve and valve springremoval
TOOL A . 60084
4 Remove all the bolts securing the air conveyor ducting
to the cylinder head and to the crankcase, carefully
separate the panels and lift away the separate panels
ensuring no damage is caused to the mating faces.
5 Release the ignition distributor retaining bolt and lift
away the distributor.
6 Remove the fuel pump retaining bolts and also the
three fuel pipe retaining clips and lift away the fuel
pump assembly together with the insulator, gaskets
and control rod.
7 Release the t w o valve rocker retaining nuts, note the
order of assembly of washers and ease away the rocker
shaft assembly from the top of the cylinder head.
Carefully lift out the valve rocker pushrods noting
their relevent positions for correct reassembly.
8 Slacken the four cylinder head cap nuts and the four
conventional nuts in the order shown in FIG 1 :46. Lift
the cylinder head away from the barrels. If difficulty is
experienced it is essential to use Fiat tool A.40014 or a
similar drilled plate as shown in FIG 1 :9, otherwise
serious damage could be caused if other means are
used.
9 Remove the four pushrod sleeves and the casing con-
taining the oil ducting to the overhead valve gear.
10 Remove the six screws holding the centrifugal oil filter
pulley cover and lift away the cover. Remove the
centrifugal filter mounting flange by unscrewing the
crankshaft central bolt. Also remove the timing cover
f r o m t h e rear of t h e crankcase. Note carefully the posi-
tion of the nuts, toothed and plain washers for correct
reassembly.
11 Release the four camshaft sprocket retaining bolts
and lift away the sprocket and timing chain. Using
Fiat puller A.46020 or a large universal two-leg puller
as shown in FIG 1 : 1 0 remove the crankshaft
sprocket and its key
12 Carefully lift out the rocker pushrod tappets making a
note of their location and gently pull out the camshaft
making sure that the front bearing bore is not
damaged by the cam lobes.

sections of the air conveyor securing with seven
screws, seven toothed washers and five nuts.
22 Slide the fuel pump control rod into its seating,
assemble the insulator between oil wetted graphite
gaskets and fit the pump to the crankcase using nuts
and toothed washers.
23 Fit the air conveyor cover complete with the accelera-
tor control relay lever and rod. Secure using eight
mounting screws, eight toothed washers, eight plain
washers and eight nuts. Fit the fuel line retaining clip
which is secured by one of the air conveyor upper
screws. Install the generator and fan drive pulley
having first placed four adjusting rings between the
pulley halves and the thrust ring on the outside.
Secure the pulley to generator shaft using three
screws and three toothed washers. Fit the generator
fan drive belt.
24 Refit the carburetter having first positioned the
bakelite heat shield between the t w o oil moistened
graphite gaskets. Secure the carburetter using t w o
copper washers and t w o self-locking nuts. Fit the
exhaust silencer and secure to the exhaust manifolds
with nuts and spring washers. Place the t w o graphite
gaskets between the manifold joints. Fit both exhaust
silencer upper mounting brackets and secure them
on the top side to the brackets already in place w i t h
nuts and toothed washers on the bottom side w i t h
screws and toothed washers.
25 Carefully position the distributor at a 10 deg advance
setting and secure w i t h a
nut, plain washer and
spring washer. Fit the fuel pump to carburetter line
complete w i t h mounting bracket rubber lining and
secure the line with two clamps. If difficulty is
experienced in positioning the fuel line into the pump
or carburetter funnels it is suggested that the line
ends should be heated in hot water and thoroughly
dried before installing.
26 Install the air cleaner elbow and rubber hose assembly
on the top of the carburetter using a graphite gasket
in between and secure w i t h nuts, plain washers and
spring washers. Carefully position the air cleaner, line
and hose assembly and connect it to the elbow.
Secure the cleaner to air conveyor cover using screws
and toothed washers.
27 Fit the spark plug cables complete with the rubber
grommet for cable mounting bracket on engine
cowling and connect the cables to the distributor
and spark plugs. Fit the oil pressure gauge sender
unit together w i t h its sealing washer.
28 Install the cylinder head cover and oil breather pipe
assembly w i t h a cork gasket inserted between.
Secure w i t h self-locking nuts and fibre washers.
Connect the accelerator control relay lever rod to the
carburetter and secure with the clip.
29 Fill the oil pan with the correct grade and quantity of
oil, insert the dipstick and the engine is ready for
refitting.
1:18 Engine assembly (station wagon)
Reassembly of this engine is straightforward as it is
the reverse procedure to dismantling. It is recommended
that Sections 1 :5 and 1 :17 are studied as the assembly
technique is similar for both the horizontal and vertical
F50031 cylinder engines. The following points should however
be noted:
1 Refer to FIG 1 :45 for the correct positioning of the
connecting rod-piston assembly on the 120.000
engine.
2 The sequence of tightening the cylinder head nuts is
different, the new order being given in FIG 1 :46.
Key to Fig 1 :47 1 Suspension arm 2 Screw,
rubber pad to bracket 3 Bracket-to-engine nut
4 Nut, arm to bracket 5 Arm bracket 6 Spring
7 Arm pin-to-support nut 8 Screws, pin to support
9 Pin arm to supportFIG 1 :47 Power plant rear suspension FIG 1:46 Cylinder head stud nut tightening sequence.
500 D. F and L Sedan and Station Wagon

FIG 1 :48 Power plant front support cross-section
FIG 1 :49 Checking the generator and blower drive
belt tension
1 :19 Power plant mountings
The combined power and transmission unit is elastic-
ally mounted on two supports.
The front of the unit rests on a crossmember which is
secured under the car floor through two rubber block
mountings that are bolted to the gearbox casing as
shown in FIG 1 :48. The position of the rubber blocks
on the crossmember is adjustable so that the assembly
can be correctly aligned.
W i t h t h e rear of the unit the engine crankcase is sprung
to the b o d y rear crossmember through an articulated
swinging arm that compresses a coil spring as shown in
FIGS 1 :47 and 1 :49. A rubber bump pad is mounted
inside the spring to give a progressive action.
Whenever the power and transmission unit is being
serviced the condition of the mountings should be
checked and any worn or damaged parts renewed.
1 :20 Adjustment of generator and fan drive belt
The centrifugal oil filter cover/pulley on the crankshaft
transmits the drive through a V-belt to the generator and
centrifugal fan pulley.
32
(b) Engine stalls
1 Check 1, 2, 3, 4, 10, 1 1 , 12, 13, 14 and 15 in (a)
2 Sparking plugs defective or gaps incorrect
3 Retarded ignition 1 Defective coil
2 Faulty distributor capacitor (condenser)
3 Dirty, pitted or incorrectly set contact breaker points
4 Ignition wires loose or insulation faulty
5 Water on sparking plug leads
6 Corrosion of battery terminals or battery discharged
7 Faulty or jammed starter
8 Sparking plug leads wrongly connected
9 Vapour lock in fuel pipes
10 Defective fuel pump
11 Overchoking
12 Underchoking
13 Blocked petrol filter or carburetter jets
14 Leaking valves
15 Sticking valves
16 Valve timing incorrect
17 Ignition timing incorrect
(a) Engine will not start 1 :22 Fault diagnosis
Since its introduction the Fiat new 5 0 0 model has
been continually developed. The main modifications that
have been made are as follows:
1 Heating system safety device
2 Recirculation device for the blow-by gases
3 Cylinder head modified to incorporate item 1
4 Double valve springs fitted
5 Cylinder barrels modified to incorporate item 1
6 Flywheel modified to incorporate new type diaphragm
spring clutch mounting
7 Larger air cleaner container.
Details of these modifications are to be found in the
relevant sections if they necessitate a change in service
overhaul procedure. Other information is to be found in
Technical Data.
1 :21 Modifications
When the V-belt has been correctly adjusted the belt
should sag 13/32 inch under a hand pressure of about 22 lb
as shown in FIG 1 : 4 9.
Should the belt be too slack the generator and
centrifugal fan will not operate at the correct speed
causing overheating and a discharged battery. Also the
belt will slip causing rapid wear of the belt. Conversely
if the belt is too tight excessive loading will be placed
on the generator bearings causing excessive bearing
wear and noisy operation.
To adjust the belt tension proceed as follows:
1 Remove the three nuts ' B ' (see FIG 1 :49) on the
generator pulley and this will split the pulley into two
parts between which are spacer rings.
2 The tension of the belt is increased or decreased by
either reducing or increasing the number of spacers.
3 Place the spacer rings removed from between the
pulley halves on the pulley outer face so that the rings
may be re-inserted when fitting a new belt.
4 Tighten the three nuts to a torque wrench setting of
14.5
lb ft.
Key to Fig 1 :49 A Normal give-in: about 13/32 inch under
a 22 Ib pressure B Nuts securing the pulley halves with
spacer rings

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 26.1MB2 : 7 Modifications
2 : 8 Carburetter operation and adjustment,
Weber 26.OC
2 :9 Air cleaner
2 : 1 0 B l o w - b y 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 o i l 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 t w o nuts and washers holding pump to
crankcase.
3 Carefully lift away the pump, gaskets and insulating pad
from the crankcase (see FIG 2 : 3).
F50035

CONTROL ROCKER FROM TANK TO CARBURETOR
FIG 2 : 1 Fuel pump. Arrows point to fuel inlet and outlet
FIG 2 : 2 Fuel pump components
KeytoFig2:2 1 Cover screw 2 Screw gasket3 Cover gasket 4 Cover 5 Upper body
6 Spring for inlet valve 7 Inlet valve 8 Outlet valve
9 Spring for outlet valve 10 Plate gasket 11 Plate screws
12 Valve retaining plate 13 Filter gauze 14 Diaphragm,
complete with tie rod 15 Return spring 16 Spring
thrust cup 17 Felt 18 Washer for felt
1 9 Connection screws 20 Lower body 21 Rocker
22, 24 Gaskets 23 Insulating pad 25 Pump control
pushrod
36
FIG 2 : 3 Fuel pump and control pushrod
FUELPUMP CONTROLPUSHROD
INSULATING
PAD
FUEL PUMP
A l l 500 Sedans are equipped with Weber type 26. IMB
carburetters w i t h detail differences only between the
models. The carburetter is of a downdraft single choke 2 : 6 Carburetter operation and adjustment,
Weber 26.IMB Carefully slide the pump control pushrod into the
crankcase, assemble the t w o gaskets w i t h the insulating
pad in between and slide over the pump retaining studs.
Ease t h e p u m p towards the crankcase ensuring the push-
rod locates correctly in the rocker end. Finally tighten the
two retaining nuts and spring washers. Installation:Ensure t h a t all parts are clean and dry. Assembling is the
reverse procedure of dismantling. Lubricate the rocker
lever and pin before placing them in the lower body. 2 : 5 Reassembly, installation and adjustment 1 Refer to FIG 2 : 2 and remove the cover mounting
screw 1 and washer 2. Lift off cover 4 and filter 13.
Mark the relative position of the two halves of the pump
body. Remove the pump bodies interlocking screws 19
and separate the upper half from the lower half of the
body.
2 Push down the centre of the diaphragm assembly 14
and rotate through 90 deg. to release diaphragm from
the rocker 2 1 . Lift out diaphragm and spring 15.
3 Release the t w o valve assemblies in the upper body by
removing the valve retaining plate locking screws 1 1 ,
and lifting out the plate 12, gasket 10, valve springs 6
and 9, and valves 7 and 8.
4 Using a pin punch remove the rocker pivot pin together
w i t h the t w o washers and carefully lift away rocker and
reaction spring.
5 Thoroughly wash all components in petrol and
blow
dry with compressed air or a foot pump. Inspect the
valves 7 and 8 for evidence of damage and valve springs
6 and 9 for weakness or cracks. Check to see that the
diaphragm reaction spring and rocker are not distorted
or unserviceable. Generally inspect all parts for cracks,
distortion and the diaphragm for stiffness and also the
rocker and pin for wear. Dismantling:

Air cleaner—station wagon:
A pleated paper air cleaner element is housed in a
special air intake chamber connected to the front of the
engine air cooling cowling (see FIG 4 : 2) . This chamber
will be seen located towards the rear of t h e power unit
compartment. Remove the retaining wing nut, lift off the
lid and the element can be withdrawn by lifting upwards.
2:10 Blow-by-gases recirculation device
Engine 110 F.000
All the oil vapours and blow-by-gases that are formed
in the engine crankcase are drawn to the cylinder head
cover recess 1 (see FIG 2:18). From here they travel into
the pipe 5 via a breather valve 2 which is firmly attached to
the oil filler cap 3 and the strainer 4 located in the filler
neck. The oil vapours and gases are then d r a w n back into
the duct 9 from the pipe 5 which connects the air cleaner
6 to the carburetter 7. This ensures a complete closed cir-
cuit circulation.
Engine 120.000:
From engine No. 288156 the oil vapours and blow-by-
gases instead of being exhausted to the atmosphere are
conveyed to the air cleaner and from here they are drawn
back into the combustion chambers. To ensure that an
excessive of oil vapour does not pass along the piping
with the blow-by-gases a diaphragm is fitted in the duct
in front of the breather valve 2 (see FIG 2 :18), the dia-
phragm comprising a filter gauze 11 and moveable parti-
tion 10.
It should be noted that the oil vapour strainer 4 (see
FIG 2:18) and the flame trap 8 can easily be removed
from their seating for cleaning or renewal.
2 : 1 1 Fuel tank
The fuel tank is located in the front compartment as
shown in FIG 2:19, it comprises a filler union fitted with a
cap, a fuel reserve supply indicator sender unit and a con-
nection incorporating a filter for the main fuel supply pipes.
To remove the tank proceed as follows:
1 Remove the contents of the front compartment includ-
ing the spare wheel and tool bag.
2 Disconnect the main fuel line at the sender unit and also
disconnect the cable to the fuel reserve supply indicator.
3 Remove the four screws together w i t h the clips that fix
the tank to the body and carefully lift away the fuel tank.
4 Carefully drain the contents of the tank into a clean dry
container of a suitable capacity.
Fuel tank—sedan (110 F.) and station wagon (120):
The fuel tank is arranged in the front compartment as
shown in FIG 2 :20. To remove the fuel tank proceed as
follows:
1 Remove both screws which secure the front ends of the
clamping bands to the dash panel. The screws are
shown by arrows in FIG 2 :20.
Petrol tank cleaning:
The tank must be thoroughly checked for leaks espe-
cially at the joint seams. Should a leak be found it is
F50045
advisable for a garage to attend to this as it is very dange-
rous to apply heat to a petrol tank without first taking strict
precautions and a garage will be in a better position to do
this. To clean the tank interior, remove the drain plug and
spray in a jet of air or petrol so that all sediment and dirt
deposits can be loosened. Then vigorously shake the tank.
Flush the tank w i t h petrol and blow the tank dry. Repeat
this procedure until the tank is clean. Refit the drain plug.
Whilst the petrol tank is away from the car it is advisable
to disconnect the fuel feed pipes at the pump and the
carburetter and ensure that these are clear by using an air
jet to one end of the pipe.
Key t o Fig 2 :20
Note Arrows point to fuel tank clamping band screws vent valve
indicator tank unit1 Fuel tank2 Filler cap with
3 Fuel suction pipe and reserve supply
4 Tank clamping bands
FIG 2:20 Location of the fuel tank in front compart-
ment, 500F, L FIG 2:19 Fuel tank in front compartment. The fuel
reserve supply indicator (red light) glows when fuel
amount in tank is less than .8 to 1.1 Imp galls, or 5 litre FUEL TANK
FUEL LINE TO PUMP
FUEL GAUGE CABLE

2:12 Fault diagnosis
(a) Leakage or insufficient fuel delivered
1 Air vent in tank restricted
2 Petrol pipes blocked
3 Air leaks at pipe connections
4 Pump or carburetter filters blocked
5 Pump gaskets faulty
6 Pump diaphragm defective
7 Pump valves sticking or seating badly
8 Fuel vapourizing in pipelines due to heat
(b) Excessive fuel consumption
1 Carburetter needs adjusting
2 Fuel leakage
3 Sticking controls or choke device
4 Dirty air cleaner
5 Excessive engine temperature
6 Brakes binding
7 Tyres under-inflated
8 Idling speed too high
9 Car overloaded(c) Idling speed too high
1 Rich fuel mixture
2 Carburetter controls sticking
3 Slow-running screws incorrectly adjusted
4 Worn carburetter butterfly valve
(d) Noisy fuel pump
1 Loose mountings
2 Air leaks on suction side and at diaphragm
3 Obstruction in fuel pipe
4 Clogged pump filter
(e) No fuel delivery
1 Float needle stuck
2 Vent in tank blocked
3 Pipeline obstructed
4 Pump diaphragm stiff or damaged
5 Inlet valve in pump stuck open
6 Bad air leak on suction side of pump
46