Mitsubishi MOTORS Space Runner 1999 Workshop Manual Supplement page 549

13B-68
Symptom
Fuel pressure too low
Fuel pressure drops after racing Fuel pressure drops after racing
No fuel pressure in fuel return
hose
Fuel pressure too high
Same fuel pressure when vacuum
hose is connected and when
disconnected
Symptom
Fuel pressure drops gradually after
engine is stopped engine is stopped
Fuel pressure drops sharply
immediately after engine is stopped
MPI –
On-vehicle Service
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
15. Stop the engine and check change of fuel pressure gauge
reading. Normal if the reading does not drop within 2
minutes. If it does, observe the rate of drop and
troubleshoot and repair according to the table below.
Probable cause
Leaky injector
Leaky fuel regulator valve seat
Check valve in fuel pump is held open
16. Release residual pressure from the fuel pipe line.
(Refer to P.13B-69.)
17. Remove the fuel pressure gauge and special tool from
the delivery pipe.
Caution
Cover the hose connection with rags to prevent splash
of fuel that could be caused by some residual pressure
in the fuel pipe line.
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
Remedy
Replace injector
Replace fuel pressure regulator
Replace fuel pump