Fuel Pressure (Optima & Magentis (Canadian))
- Release fuel pressure. See FUEL PRESSURE RELEASE . Disconnect high-pressure fuel hose from fuel delivery pipe. Cover hose connection using rags to avoid spraying of fuel.
- Using Fuel Pressure Gauge Adapter (09353-38000), install fuel pressure gauge to fuel delivery pipe. See Fig 1 or Fig 2 . Torque fuel gauge adapter bolts to 18-26 ft. lbs. (24-35 N.m). Connect negative battery cable.
- Using fuel pump check terminal connector, activate fuel pump and ensure no fuel leakage is present at pressure gauge or connection. See PRIMING FUEL SYSTEM . If no leaks are present, start engine and allow to idle.
- Disconnect vacuum hose from fuel pressure regulator, and plug hose end. Measure and record fuel pressure at idle. Reconnect vacuum hose, and again measure and record fuel pressure. See FUEL PRESSURE SPECIFICATIONS table. If fuel pressures are not within specification, go to next step. If measurements are okay, go to step 8.
- If fuel pressure is less than specified, check following conditions:
- Restricted fuel filter.
- Fuel pressure regulator leaking fuel to fuel return side.
- Leaking in-tank fuel pick-up hose.
- Low fuel pump discharge pressure.
Repair or replace as necessary. Recheck fuel pressure.
- If fuel pressure is greater than specified, check for sticking fuel pressure regulator. A restricted or bent fuel return hose or pipe. Repair or replace fuel hose or pipe and fuel pressure regulator. To replace fuel pressure regulator, see FUEL PRESSURE REGULATOR under FUEL SYSTEM in REMOVAL, OVERHAUL & INSTALLATION article.
- If fuel pressure does not change when regulator vacuum hose is connected and disconnected, check for following conditions:
- Restricted or damaged vacuum hose.
- Restricted manifold vacuum port.
- Sticking or poorly seated fuel pressure regulator valve.
Repair or replace as necessary. Recheck fuel pressure.
- If fuel pressures are as specified, stop engine and check for decrease in fuel pressure gauge. Fuel pressure should hold for approximately 5 minutes. If fuel pressure decreases slowly after engine is stopped, check for leaking injector. See FUEL INJECTOR LEAKAGE TEST , under FUEL INJECTORS. Replace as necessary. If fuel pressure decreases immediately after engine is stopped, check-valve inside fuel pump is not working. Replace fuel pump. To replace fuel pump, see FUEL PUMP under FUEL SYSTEM in REMOVAL, OVERHAUL & INSTALLATION article. After repairs are completed, recheck fuel pressure.
- After testing is completed, release fuel pressure. See FUEL PRESSURE RELEASE . Disconnect fuel pressure gauge from adapter. Ensure hose connection is covered by shop towel to prevent fuel spray. Remove adapter bolts and adapter. Install NEW "O" ring, and reinstall fuel line with original bolts. Apply battery voltage to fuel pump drive connector terminal. See Figure. Check for fuel leaks. Repair any leaks as necessary.