Mitsubishi MOTORS Space Runner 1999 Workshop Manual Supplement page 148

Symptom
D Fuel pressure too low
D Fuel pressure drops after racing
D
No fuel pressure in fuel return
hose
Fuel pressure too high
Same fuel pressure when vacuum
hose is connected and when
disconnected
MPI -
On-vehicle Service
7. Select "Item No.07" from the MUT-II Actuator test to drive
the fuel pump.
Check that there are no fuel leaks from any parts.
8. Finish the actuator test or turn the ignition switch to "LOCK"
(OFF) position.
9. Start the engine and run at idle.
10. Measure fuel pressure while the engine is running at
idle.
Standard value: Approx. 265 kPa at kerb idle
11. Disconnect the vacuum hose from the fuel pressure
regulator and measure fuel pressure with the hose end
closed by a finger.
Standard value: 324 - 343 kPa at kerb idle
12. Check to see that fuel pressure at idle does not drop
even after the engine has been raced several times.
13. Racing the engine repeatedly, hold the fuel return hose
lightly with fingers to feel that fuel pressure is present
in the return hose.
NOTE
If the fuel flow rate is low, there will be no fuel pressure
in the return hose.
14. If any of fuel pressure measured in steps 10 to 13 is
out of specification, troubleshoot and repair according
to the table below.
Probable cause
Clogged fuel filter
Fuel leaking to return side due to poor
fuel regulator valve seating or settled
spring
Low fuel pump delivery pressure
Binding valve in fuel pressure
regulator
Clogged fuel return hose or pipe
Damaged vacuum hose or clogged
nipple
Remedy
Replace fuel filter
Replace fuel pressure regulator
Replace fuel pump
Replace fuel pressure regulator
Clean or replace hose or pipe
Replace vacuum hose or clean nipple
13D-83