Chevrolet Light Duty Truck 1973 Service Manual page 470

6 M - 4 6 ENGINE FUEL
ROCHESTER CARBURETOR DIAGNOSIS
PO SSIBLE CAUSE
D irt in pump passages or pump jet.
Fuel level.
Leaking air horn to float bowl gasket.
Carburetor loose on manifold.
Problem:
Carburetor th ro ttle valve not going wide open.
by pushing accelerator pedal to floor).
D irty or plugged fuel filters.
Power system not operating.
Metering rod not adjusted to specification.
Float level too low.
Float not dropping far enough into float bowl.
Main metering jet or metering rod d irty, plugged or in­
correct part.
Problem:
Choke valve not opening completely.
Engine flooded - Carburetor flooding.
No fuel in carburetor.
Leaking float bowl.
N O P O W E R O N H E A V Y A C C E L E R A T I O N
O R A T H IG H SP EE D
(Check
e n g i n e s t a r t s h a r d
MODELS M, MV
C O R R E C T IV E ACTION
Clean and Blow out with compressed air.
Check fo r sticking float needle or binding float. Free up
or replace parts as necessary.
to specification. Use procedure A.
Torque air horn to float bowl using proper tightening
procedure. Use procedure J.
Torque carburetor to manifold bolts. (10-14 ft. lbs.).
Adjust th ro ttle linkage to obtain wide open throttle in
carburetor.
Replace w ith a new filte r element.
Check power piston fo r free up and down movement.
If power piston is sticking check power piston and cavity
for dirt, or scores. Check power piston spring for dis­
tortion. Clean or replace as necessary.
Adjust metering rod. Use procedure B.
1. Check and reset float level to specification.
procedure A.
Check fo r binding float hanger and fo r proper float align­
ment in float bowl.
1. If the main metering jets are plugged or d irty and exces­
sive d irt is in the fuel bowl. The carburetor should be
completely disassembled and cleaned.
2. Check the jet or rod for being the correct part. Consult
the parts list for proper usage.
stamped on the jet face are the same as the last two
digits of the part number.
can be identified using chart.
Use procedure K.
w h e n h o t
1. Check for binding choke valve and/or linkage.
and free-up or replace parts as necessary.
Do not oil choke linkage.
2. Check and adjust choke thermostatic coil.
Use procedure FI or I.
See procedure under "Engine cranks, w ill not start" . Pg. 1
1. Check fuel pump. Run pressure and volume test.
2. Check float needle fo r sticking in seat, or binding float.
Fill bowl w ith fuel and look for leaks.
4
Check and reset float level
Use
The last two digits
The metering jet and rod
Clean
LIGHT DUTY TRUCK SERVICE MANUAL