GMC 1976 ZEO 6083 Maintenance Manual page 351

ENGINE FUEL SYSTEM
6M- 9
ENGINE IDLES ROUGH AND STALLS
Possible Cause Corrective Action
Choke coil rod out of adjustment . Adjust choke coil rod.
Choke valve and/or linkage 1 . Clean and align choke valve and linkage.
sticking or binding. Replace if necessary.
2. Re-adjust if part replacement is necessary.
Idle speed setting.
Adjust idle speed to specifications on decal in
engine compartment.
Not enough fuel in carburetor . 1 . Test fuel pump pressure and volume, as outlined
in service manual .
2. Check for partially plugged fuel inlet filter .
Replace, if dirty.
3 . Check fuel tank lines and tank vent lines for
blockage . Clean as necessary .
4. Remove air horn and check float adjustment .
Carburetor flooding 1 . Check all fuel filters for dirt . Clean and
replace as necessary.
NOTE : Check for flooding by
using procedure outlined under
"Engine cranks - will not
start - engine flooded" Page 8.
2. If carburetor still floods, remove air horn and
check float needle and seat for proper seal . If a
needle seat tester is not available, mouth
suction can be applied to the needle seat with
needle installed. If needle seat leaks, replace
with a factory matched set.
3 . Check for fuel leaks into float, bent float
arms or binds in 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 .
4. Check float adjustments.
5. If excessive dirt is found in the carburetor,
clean fuel system and carburetor .
Possible Cause Corrective Action
Idle speed setting.
Re-set idle speed per instructions on decal in
engine compartment.
Manifold vacuum hoses discon-
Check all vacuum hoses leading into the manifold
nected or improperly installed .
or carburetor base for leaks or disconnection.
Install or replace as necessary.
Carburetor loose on intake
Torque carburetor to manifold bolts (to 15 ft . lbs.) .
manifold .