Chevrolet Light Duty Truck 1973, Руководство по обслуживанию

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6 M - 6 0 ENGINE FUEL
ROCHESTER CARBURETOR DIAGNOSIS - ALL MODELS 4M, 4M V - FOUR BARREL
Problem:
E N G I N E S T A R T S A N D S T A L L S (Cont.)
POSSIBLE CAUSE
CORRECTIVE ACTION
Carburetor flooding,
(continued)
3. Check float for being loaded w ith fuel, bent float arms
or binds in float hanger.
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 float assembly.
4. Check float adjustments. Use procedure A.
5. If excessive d irt is found in the carburetor, clean fuel
system and carburetor.
_ ■ , E N G I N E I D L E S R O U G H
Problem :
a n d s t a l l s
Idle speed setting.
Re-set idle speed per instructions on decal in engine com­
partment.
Manifold vacuum hoses disconnected or improperly in­
stalled.
Check all vacuum hoses leading into the manifold or carbu­
retor base for leaks or being disconnected. Install or re­
place as necessary.
Carburetor loose on intake manifold.
Torque carburetor to manifold bolts (10-14 ft. lbs.).
Intake manifold is loose or gaskets are defective. Using a pressure oil can, spray light oil or kerosene around
manifold legs and carburetor base. If engine RPM changes,
tighten or replace the manifold gaskets or carburetor base
gaskets as necessary.
Hot idle compensator not operating (where used).
Normally the hot idle compensator should be closed when
engine is running cold and open when engine is hot (approx.
140°F at comp.) replace if defective.
A ir leaks into carburetor idle channels.
Tighten all carburetor screws. If gaskets are hard or cracked,
replace as necessary. Use procedure I fo r tightening air
horn screws.
Poor secondary th ro ttle valve alignment. If mis-aligned, loosen screws, align valves, tighten screws
and re-stake as necessary.
Carburetor flooding.
NOTE: Check by using procedure outlined under engine
flooded. Page 1.
1. Remove air horn and check float adjustments.
Use procedure A.
2. Check float needle and seat fo r proper seal. If a needle
seat tester is not available, mouth suction can be applied
to the needle seat w ith needle installed. If needle and
seat are defective, replace w ith factory matched set.
3. Check float fo r being loaded w ith fuel, bent float arm
or binding float hanger.
NOTE: A solid float can be checked for fuel absorption
by lightly squeezing between fingers. If wetness appears
on surface or float feels heavy (check w ith known good
float), replace float assembly.
D irt in idle channels.
If excessive d irt is found in carburetor or idle channels,
clean fuel system and carburetor. Replace fuel filters as
necessary.
3
LIGHT DUTY TRUCK SERVICE MANUAL