Hyundai Sonata 1991 Shop Manual page 261

MPI SYSTEM
10. Reduce the fuel pressure in the fuel line.
11. Disconnect the high pressure hose and remove the fuel pres-
sure gauge from the delivery pipe.
CAUTION
Cover the hose connection with a shop towel to prevent
a splash of fuel that could be caused by residual pressure
in the fuel line.
12. Install a new O-ring in the groove at the end of the
high-pressure hose.
13. Connect the high pressure fuel hose to the delivery pipe, and
tighten the screws to the specified torque.
14. Check for fuel leaks.
o Apply battery voltage to the fuel pump drive terminal to
operate the fuel pump.
o With pressure, check the fuel line for leaks.
NOTE
If there is a problem with the change in vacuum, it is pos-
sible that the throttle body port may be restricted and
require cleaning.
Checking Condition
Engine coolant temperature: 80-95°C (176-203°F)
1. Disconnect the vacuum hose from the throttle body EGR vac-
uum fitting and connect a hand vacuum pump to the fitting.
2. Start the engine and check to see that, after raising the
engine speed by racing the engine, vacuum raises proportion-
ately with the rise in engine speed.
EGR Valve Control Vacuum Check
Y31DSOA
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Engine speed (rpm)
31Y056
31-36