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PART 10-1-
GENERAL FUEL SYSTEM SERVICE
10-3
FUEL PUMP, TANK AND LINES DIAGNOSIS GUIDE
LOW FUEL PUMP
PRESSURE OR VOLUME
HIGH FUEL PUMP
PRESSURE OR VOLUME
LOW FUEL PUMP
VACUUM
LOW FUEL PUMP
VOLUME WITH NORMAL
PRESSURE
FUEL PUMP LEAKS FUEL
FUEL PUMP LEAKS OIL
FUEL PUMP NOISI
FUEL TANK AND/OR
INLET LIN! HOSIS
COLLAPSED
Dirt accumulation in the fuel and
air passages, improper idle adjust-
Diaphragm stretched or leaking.
Fuel pump diaphragm spring is
weak.
Rocker arm or eccentric worn or
undersize.
Excessive clearance between rock-
er arm and fuel pump link.
Fittings loose or cracked.
Diaphragm spring too strong or
improper
spring.
Diaphragm
surface
too
tight
(over-tensioned).
Diaphragm stretched or leaking.
Fuel pump springs weak.
Fuel pump valves improperly seat-
in g.
Diaphragm ruptured.
Fuel filter clogged.
Fuel pump to carburettor inlet line
obstructed, crimped or
leaks.
Diaphragm defective.
Fittings loose.
Fuel pump retaining bolts loose.
Mounting gasket defective.
Rocker arm or eccentric worn.
Mounting bolts loose.
Rocker arm springs weak or
broken.
Fuel tank vent restricted.
ments and improper fuel level are
the major sources of carburettor
CARIURmOR DIAGNOSIS GUIDI
FLOODING OR UAKING
CARBURETOR
HARD STARnNG
Cracked carburettor body.
Defective main body and for fuel
bowl gasket.
High fuel level or ftoat setting.
Fuel inlet needle not seating prop-
erly or worn needle and/ or seat.
Improper starting procedure caus-
ing a flooded engine.
Improper carburettor fuel level.
Improper idle adjustments.
Sticking or incorrectly seating fuel
inlet needle.
Incorrect fuel pump pressure.
Fuel filter clogged (low volume).
Fuel line cracked or broken.
Fuel
pump
valves
improperly
seating.
Dirt in fuel tank and/ or lines.
Fuel tank vent restricted.
Diaphragm ruptured.
Main body retaining screws loose.
Pump link has no free play (fro-
zen).
Diaphragm vent opening plugged
or
omitted.
Rocker arm or eccentric
worn.
Excessive clearance between rock-
er arm and fuel pump
link.
Main body retaining screws loose.
Restriction in fuel supply line to
fuel pump.
Threads on fittings
stripped.
Body cracked.
Diaphragm pull rod oil seal rup-
lured or improperly installed.
Rocker arm bumper pad defec-
tive.
troubles.
Ruptured accelerating pump dia-
phragm.
Excessive fuel pump pressure.
Defective power valve gasket,
Ruptured power valve
diaphragm.
Improper carburettor gasket and
/
or spacer combination.
Incorrect setting of choke thermo-
static spring housing.
Choke linkage or plate
binding.
Binding qr broken manual choke
linkage.
Restrictions or air leaks in the
choke vacuum or hot air passages.
Dirty air cleaner element.
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