GMC 1976 ZEO 6083 Maintenance Manual page 352

6M- 10 ENGINE FUEL SYSTEM
ENGINE HESITATES ON ACCELERATION
Possible Cause Corrective Action
Intake manifold is loose or Using a pressure oil can, spray light oil or kero-
gaskets are defective. sene around manifold legs and carburetor base . If
engine RPM changes, tighten or replace the mani-
fold gaskets or carburetor base gaskets as
necessary.
Hot idle compensator not Normally the hot idle compensator should be closed
operating (where used).
when engine is running cold and open when engine
is hot (approx. 140°F at comp .) replace if
defective .
Air leaks into carburetor idle Tighten all carburetor screws . If gaskets are hard
channels . or cracked, replace as necessary.
Poor secondary throttle valve If mis-aligned, loosen screws, align valves,
alignment. tighten screws and re-stake as necessary.
Carburetor flooding . 1 . Remove air horn and check float adjustments.
NOTE : Check by using procedure
outlined under "engine flooded" .
2 . Check float needle and seat for proper seal .
Page 6M-8 .
If a needle seat tester is not available, mouth
suction can be applied to the needle seat with
needle installed . If needle and seat are defective,
replace with factory matched set .
3. Check float for fuel leaks, bent float arm or
binding float hanger.
NOTE : A solid float can be checked for fuel absorp-
tion by lightly squeezing between fingers. If wet-
ness appears on surface or float feels heavy (check
with known good float), replace float assembly .
Dirt in idle channels .
If excessive dirt is found in carburetor or idle
channels, clean fuel system and carburetor .
Replace fuel filter as necessary.
Possible Cause
Corrective Action
Defective accelerator pump
1 . Remove carburetor air horn and check pump cup.
system . If cracked, scored or distorted, replace pump
NOTE: A quick check of the pump plunger. Check pump discharge ball for proper
system can be made as follows. seating and location .
With the engine off, remove air
cleaner and look into carburetor
bores and observe pump shooters,
To check discharge ball for proper seating, fill
while briskly opening throttle
cavity above discharge ball with fuel . If "leak
valves . A full stream should emit
down" occurs remove discharge ball and clean
from each pump jet and enter
check ball seat and pump passages and jets . If
the center of the carburetor
clean, stake discharge ball seat by tapping ball
bore .
lightly against seat with drift punch and small
hammer . Replace with new discharge ball .