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Home >> Mitsubishi >> 2003 >> Eclipse GT, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Diagnostic Procedures >> Fuel System >> Fuel Pressure >> Using Fuel Pressure Gauge Set (MB991637)
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Using Fuel Pressure Gauge Set (MB991637)

  1. Remove the union joint and bolt from Adaptor Hose (MD998709) and instead, attach Hose Adaptor (MD998742) to the adaptor hose.
  2. Install Fuel Pressure Gauge Set (MB991637) to assembled hose and adaptor via a gasket.
  3. Install the assembled fuel pressure measurement tools between the fuel rail and the high-pressure fuel hose. See Fig 1.
    CAUTION: To prevent damage to the scan tool, always turn the ignition off before connecting or disconnecting it.
  4. Connect Scan Tool (MB991502) to the data link connector.
  5. Use the Actuator Test 07 to drive the fuel pump. Check that there is no fuel leaking from any section when the fuel pump is operating.
  6. Stop the fuel pump.
  7. Start the engine and run at idle.
  8. Measure fuel pressure while the engine is running at idle. See FUEL PUMP PERFORMANCE  table.
  9. Disconnect the vacuum hose from the fuel pressure regulator and measure fuel pressure with the hose end closed with your finger. See FUEL PUMP PERFORMANCE  table.
    Fig 1: Installing Fuel Pressure Gauge Set (MB991637)
    G00229863Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  10. Check to see that fuel pressure at idle does not drop even after the engine has been revved several times.
  11. While revving the engine repeatedly, hold the fuel return hose lightly with your 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.
  12. If any of the fuel pressures measured in steps  10- 13 are out of specification, trouble shoot and repair according to FUEL PRESSURE TROUBLE SHOOTING  table.
  13. Stop the engine and observe fuel pressure gauge reading. It is normal if the reading does not drop within two minutes. If it does, observe the rate of drop and trouble shoot and repair according to FUEL PRESSURE DROP TROUBLE SHOOTING  table. Start, then stop the engine.
    1. Squeeze the fuel return line closed to confirm leak-down occurs from defective fuel pressure regulator.
    2. Squeeze the fuel supply line closed to confirm leak-down occurs from defective fuel pump check valve.
    3. If pressure continues to drop with both fuel lines squeezed closed, injector(s) are leaking.
  14. Release residual pressure from the fuel pipe line. See FUEL SYSTEM PRESSURE RELEASE .
    WARNING: Cover the hose connection with shop towels to prevent splash of fuel that could be caused by some residual pressure in the fuel pipe line.
  15. Remove the fuel pressure gauge set, and hose and adaptor from the fuel rail.
  16. Replace the O-ring at the end of the high-pressure fuel hose with a new one.
  17. Fit the high-pressure fuel hose into the fuel rail and tighten the bolts to 37-53 INCH lbs. (4-6 N.m).
  18. Use the scan tool to operate the fuel pump and check the fuel line for any leaks. Repair as needed.
  19. Disconnect the scan tool.
FUEL PUMP PERFORMANCE

Application At Idle w/Vacuum - psi (kPa) At Idle w/o Vacuum - psi (kPa)
All Models (Except Lancer Evolution VIII) 39 (270) 47-50 (330-350)
Lancer Evolution VIII 33 (230) 42-45 (289-309)
FUEL PRESSURE TROUBLE SHOOTING

Symptoms Probable Cause Remedy
Fuel pressure too low, fuel pressure drops after racing, no fuel pressure in fuel return hose. Clogged fuel filter. Replace fuel filter.
..... Fuel leaking to return side due to poor fuel regulator valve seating or settled spring. Replace fuel pressure regulator.
..... Low fuel pump delivery pressure. Replace fuel pump.
Fuel pressure too high. Binding valve in fuel pressure regulator. Replace fuel pressure regulator.
..... Clogged fuel return hose or pipe. Clean or replace hose or pipe.
Same fuel pressure when vacuum hose is connected and when disconnected. Damaged vacuum hose or clogged nipple. Replace vacuum hose or clean nipple.
..... Defective fuel pressure regulator. Replace fuel pressure regulator.
FUEL PRESSURE DROP TROUBLE SHOOTING

Symptoms Probable Cause Remedy
Fuel pressure drops gradually after engine is stopped. Leaky injector. Replace injector.
..... Leaky fuel regulator valve seat. Replace fuel pressure regulator.
Fuel pressure drops sharply immediately after engine is stopped. Check valve in fuel pump is held open. Replace fuel pump.
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