Mitsubishi Stealth 1994 Import Service Manual page 689

MULTIPORT FUEL INJECTION -
Condition
After the engine is stopped, the
fuel pressure drops gradually.
There is a sudden sharp drop of
the fuel pressure immediately
after the engine is stopped.
On-Vehicle Inspection of MFI Components
(13)Stop the engine and check for a change of the value
indicated by the fuel pressure gauge. The condition is
normal if there is no decrease of the indicated value within
two minutes.
If there is a decrease of the indicated value, monitor the
speed of the decrease, and, referring to the table below,
d e t e r m i n e t h e c a u s e o f t h e p r o b l e m a n d m a k e t h e
appropriate repair.
Probable cause
The check valve (within the fuel
pump) is not closed.
(14)Reduce the internal pressure of the fuel pipes and hoses.
(15)Disconnect the fuel pressure gauge and the special tools
from the delivery pipe.
Caution
Because there will be some residual pressure in the fuel
pipe line, use a shop towel to cover so that fuel doesn't
splatter.
(16)Replace the O-ring at the end of the fuel high-pressure hose
with a new one.
tighten the installation bolt at the specified torque.
Tightening torque: 5.0 Nm (3.6 ft.lbs.)
the fuel pump so as to activate the fuel pump.
line.
Remedy
Replace the injector.
Replace the fuel pressure regulator.
Replace the fuel pump.