LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Jeep >> 1994 >> Wrangler S, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Fuel System >> Fuel Delivery >> Fuel Pressure Leak-Down Test
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Fuel Pressure Leak-Down Test

  1. Remove cap from pressure fitting on fuel rail. See Figure . Connect a 0-100 psi (0-7.0 kg/cm2 ) fuel pressure gauge to pressure fitting on fuel rail. Start and run engine at idle.
  2. Turn engine off and note fuel pressure gauge reading. Leave fuel pressure gauge connected. Allow 30 minutes to elapse and then compare fuel pressure gauge reading to reading taken when engine was turned off.
  3. A pressure drop up to 20 psi (1.4 kg/cm2 ) within 30 minutes is within specification. If pressure drop is not within specification, go to next step. If pressure drop is within specification, the fuel pump outlet check valve and fuel pressure regulator are operating correctly.
  4. Release fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE PROCEDURE above. Disconnect both fuel lines at fuel rail near fuel pressure regulator. Connect 3/8" fuel hose between disconnected fuel supply line and fuel rail. Connect 5/16" fuel hose between disconnected fuel return line and fuel rail.
  5. Start engine and record fuel pressure gauge reading. Turn engine off. Pinch off hose connected to fuel return line. Allow 30 minutes to elapse. If pressure drop is within specification, go to next step. A pressure drop of more than 20 psi (1.4 kg/cm2 ) within 30 minutes indicates pressure is bleeding past fuel pump outlet check valve. Replace fuel pump assembly, located in fuel tank.
  6. Pinch off hose connected to fuel supply line. Allow 30 minutes to elapse. A pressure drop of more than 20 psi (1.4 kg/cm2 ) within 30 minutes indicates pressure is bleeding past fuel pressure regulator. Replace fuel pressure regulator.
scientia non olet · About LEMON Manuals