GMC 1976 ZEO 6083 Maintenance Manual page 369

tank filter restricted or the pump is inoperative.
Before removing pump, disconnect fuel lines at
fuel pump and at gas tank and blow through
them with an air hose to make sure they are
clear. Reconnect fuel lines to pump and gas
tank .
d. Reconnect fuel line at the carburetor,
tighten line fitting while holding carburetor fuel inlet
nut. Start engine and check for leaks.
Pump (Inlet) Vacuum
Low vacuum or complete loss of vacuum pro-
vides insufficient fuel to the carburetor to operate the
engine throughout normal speed range .
a. Disconnect hose from fuel tank to fuel
pump at the fuel pump . Fasten hose in an up position
so that fuel will not run out.
b. Connect one end of a short hose to the fuel
pump inlet and attach a vacuum gauge to the other
end. Start engine, gauge should register not less than
15 in . vacuum . If less than 15 in . of vacuum, replace
pump .
Pump (Outlet) Pressure
Even if fuel flows in good volume from line at
carburetor, it is advisable to make certain that pump
is operating within limits .
a. Disconnect fuel line at the carburetor inlet
fitting. Install a rubber hose approximately 8/10"
long over the line and attach a low reading pressure
gauge. Hold the gauge up so that it is approximately
16" above the fuel pump.
b. Start engine and run at slow idle (using
gasoline in carburetor bowl) and note reading on
pressure gauge.
REMOVAL
1 . Remove engine cover.
2. Remove wing nut on top of air cleaner.
3 . Disconnect P.C .V . pipe from the air cleaner
housing. See Figure 33 .
4. Lift air cleaner housing off carburetor high
enough to reach underneath it and disconnect the
vacuum hose from the intake manifold . See Figure
33 .
5. Remove air cleaner housing.
6. Inspect
air cleaner housing gasket on
carburetor, replace gasket as needed .
Removal
AIR CLEANER
1 . Raise vehicle .
5 . Remove pump .
Installation
4. Lower vehicle.
INSTALLATION
ENGINE FUEL SYSTEM
6M- 27
c . If pump is operating properly, the pressure
should be 5-1/2 to 6-1/2 constant . If pressure is too
high or too low or varies materially at different en-
gine speeds, the pump should be replaced .
FUEL PUMP REPLACEMENT
2 . Disconnect fuel line to carburetor and fuel
hose from fuel tank.
3. Loosen nut securing top of fuel pump to block.
4. Remove bolt securing bottom of fuel pump to
block.
1 . Install fuel pump with new gasket .
2. Install bolt and tighten alternately with nut to
assure an even draw down of pump to block.
3. Connect fuel hose and line to fuel pump .
Tighten fuel fittings to carburetor and fuel pump .
Hold nut at carburetor inlet while applying torque .
NOTE : : To install new gasket :
1 . Completely remove old gasket .
2. Remove protective paper from adhesive side of
new gasket .
3 . Install new gasket adhesive side down, on car-
buretor air horn .
1 . While installation the air cleaner housing con-
nect the vacuum hose to the intake manifold .