The manifold valve receives fuel from the metering unit.
When fuel pressure reaches ap-
proximately
3.5 psi, the valve opens and admits fuel to six ports in the manifold valve (one
port for each fuel nozzle line). The manifold valve also serves to provide a clean cutoff of
fuel to the cylinder when the engine is shutdown.
The injector nozzle lines connect the manifold valve to the six fuel injector nozzles.
The injector nozzles (one per cylinder) are "air bleed" type fuel nozzles which spray fuel
directly into the intake port of the cylinder. When the engine is running, flow through the
nozzle is continuous and will enter the cylinder combustion chamber when the intake valve
opens.
Since the size of the fuel nozzles is fixed, the amount of fuel flowing through them is
determined by the pressure applied. For this reason, fuel flow may be accurately determined
by measuring the pressure at the manifold valve. (Refer to Chapter
76
Performance Charts.)
All of the items described above are interdependent on each other to meter the correct
amount of fuel according to the power being developed by the engine.
73-10-00 SET-UP PROCEDURE
The full rich performance of the fuel injection system on all injected engines is controlled by
manual adjustment of air throttle and fuel mixture at idle and pump pressure at idle and full
throttle.
Fuel pressures of fixed orifice pumps can only be adjusted with the relief valve
screw located on the centerline at the rear of the pump. Adjustable orifice or variable orifice
(aneroid) pumps have an additional facility for adjusting pump pressure at both idle and full
throttle RPM.
73-1
0-01 TURBOCHARGED ENGINES
To make full rich adjustments on engines equipped with adjustable orifice pumps, run-up
engine to obtain
normal operating temperature
and proceed as follows:
A. Tee into either the fuel pump outlet fitting or metering unit inlet fitting (whichever is
more accessible) with an appropriate pressure gage and extended fuel line to observe fuel
pump pressures. (This gage should be properly calibrated and vented to atmosphere on all
engines).
NOTE.
.
.
Tees are already incorporated on some engine models.
B.
On all engines, back the throttle plate idle screw out of contact with the stop. Use the
throttle to hold to the specified idle RPM.
C. To obtain pressure limits specified for idle RPM the variable orifice adjusting screw on
turbocharged engines is located on the aneroid housing and
is
turned
CW
to decrease pressure
and CCW to increase pressure.
CAUTION.
.
.
Jarn Illit rltzist be looserled before screw curl be udjiisted. Use cure
ill
holll
loosertitzg and tiglttenii tg tlt
is
nut.
D.
Maintaining idle pump pressure and idle RPM, correct idle mixture exists
if,
upon
leaning with the mixture control, an increase of
25 to
50
RPM is obtained, depending on
airport elevation.
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