Pontiac FIREBIRD 1972 Service Manual page 663

ENGINE FUEL 6B-9
SPRING
OIL
RETAINER,
y
PUMP BODY
CKER ARM
Fig. 60-1 1 Fuel Pump
-
Typical
2. Discontinue fuel line at the carburetor inlet fitting.
Install a rubber hose approximately 8-10" long over
the end of the fuel line.
3. Place suitable container at end of the hose and crank
engine a few revolutions.
If little or no gasoline flows from open end of line, then
the fuel line is restricted, gas tank filter restricted or the
pump is inoperative. Before removing pump, disconnect
fuel lines at fuel pumpand 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.
4. Reconnect fuel line at the carburetor, start engine
and check for leaks.
11. 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.
1. 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.
2. Start engine and run at slow idle (using gasoline in
carburetor bowl) and note reading on pressure gauge.
3. If pump is operating properly, the pressure should be
3 to 6-1/2 constant for V-8 and 3 to 5 psi constant
for L-6. If pressure is too high or too low or varies
materially at different engine speeds, the pump
should be replaced.
When checking pressure on cars equipped with a fuel
return line. the return line must be plugged.
On fuel pumps without fuel return lines, there is an
internal bleed valve. There may be no pressure at fuel
inlet nuts at carburetor unless engine is in operation.
111. PUMP (INLET) VACUUM
Low vacuum or complete loss of vacuum provides insuffi-
cient fuel to the carburetor to operate the engine through-
out normal speed range.
1. 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.
2. 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.