Chevrolet Light Duty Truck 1973, Service Manual

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E N G IN E F U E L 6M-51
ROCHESTER CARBURETOR D IA G N O S IS
MODELS 2 G , 2 G V - T W O BARREL
E N G I N E C R A N K S ( T U R N O V E R )
W I L L N O T S T A R T O R S T A R T S H A R D W H E N C O L D
POSSIBLE CAUSE
CORRECTIVE ACTION
Improper starting procedure used.
Check w ith the customer to determine if proper starting
procedure is used, as outlined in the owner's manual.
No fuel in gas tank.
Add fuel. Check fuel gauge fo r proper operation.
Choke valve not closing sufficiently when cold.
Adjust the choke thermostatic coil. Use procedure J or K.
Choke valve or linkage binding or sticking.
Realign the choke valve or linkage as necessary. If caused
by d irt and gum, clean w ith automatic choke cleaner.
Do not oil choke linkage.
If parts are replaced, check adjustments using procedure
D, E or F.
No fuel in carburetor.
1. Remove fuel line at carburetor. Connect hose to fuel
line and run into metal container. Remove the high
tension coil wire from center tower on distributor cap
and ground. Crank over engine - if there is no fuel dis­
charge from the fuel line, check for kinked or bent lines.
Disconnect fuel line at tank and blow out w ith air hose,
reconnect line and check again for fuel discharge. If
none, replace fuel pump. Check pump fo r adequate
flow as outlined in service manual.
2. If fuel supply is o.k., check the following.
a. Inspect fuel filters. If plugged, replace.
b. If filters are o.k., remove air horn and check for a
bind in the float mechanism or a sticking float needle.
If o.k., adjust float as-specified. Use procedure A and
B or C and D.
Engine flooded.
NOTE: To check for flooding, remove the air cleaner, w ith
the engine o ff, and look into the carburetor bores. Fuel
w ill be dripping o ff nozzles and the carburetor bores w ill
be very wet.
Check to determine if customer is using proper carburetor
unloading procedure. Depress the accelerator to the floor
and check the carburetor to determine if the choke valve is
opening. If not, adjust the th ro ttle linkage and unloader,
as specified. Use procedure I.
If choke unloader is operating properly, check fo r carbu­
retor flooding.
NOTE: Before removing the carburetor air horn use the
following procedure which may eliminate the flooding.
Remove the fuel line at the carburetor and plug. Crank
and run the engine until the fuel bowl runs dry. Turn o ff
the engine and connect fuel line. Then re-start and run
engine. This w ill usually flush d irt past the carburetor float
needle and seat. If d irt is in fuel system, clean the system
and replace fuel filters as necessary. If excessive d irt is
found, remove the carburetor unit, disassemble and clean.
Check float needle and seat fo r proper seal. If a needle and
seat tester is not available, apply mouth suction to the
needle seat w ith needle installed. If the needle or seat is
defective, replace w ith a factory matched set. Check float
for being loaded w ith fuel, bent float hanger or binds in the
float arm.
NOTE: A solid float can be checked fo r fuel absorption by
lightly squeezing between fingers. If wetness appears on
surface or float feels heavy (check w ith known good float),
replace the float assembly. Check metal float for leakage
bv shakinq. Adjust float. Use procedure A and B or
C and D.
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