Fuel Pressure
Basic diagnosis of fuel system should begin by determining fuel system pressure.
CAUTION:
High fuel pressure may be present in fuel lines and component parts. Relieve pressure before attempting to open system for testing or component replacement. DO NOT allow fuel to flow onto engine or electrical parts or allow an open flame in area while testing fuel system components.
- Depressurize fuel system by disconnecting fuel pump wiring harness at fuel tank. Start engine. Let engine run until fuel is exhausted and engine stops. Turn ignition off. Disconnect negative battery cable. Connect fuel pump wiring harness connector.
- On 2.0L, remove throttle body bracket. On all models, wrap fuel lines with shop towel and disconnect high pressure fuel line at fuel rail. Install Adapters (MD998709 and MD998742) between fuel rail and high pressure fuel line. Connect fuel pump pressure gauge.
- Connect negative battery cable. Apply battery voltage to fuel pump check terminal to activate fuel pump. See Fig 1 . Check for fuel leaks. Disconnect battery voltage from check terminal. Start engine and let idle.
- Disconnect and plug fuel pressure regulator vacuum hose. Measure fuel pressure. On all models except 2.0L turbo, fuel pressure should be 47-50 psi (3.3-3.5 kg/cm2 ) at idle. On 2.0L turbo, fuel pressure should be 36-38 psi (2.5-2.7 kg/cm2 ) at idle.
- Remove plug and connect fuel pressure regulator vacuum hose. Measure fuel pressure with vacuum hose connected. On all models except 2.0L turbo, fuel pressure should be 38 psi (2.7 kg/cm2 ) at idle. On 2.0L turbo, fuel pressure should be 27 psi (1.9 kg/cm2 ) at idle.
- Increase engine speed to 2500-3000 RPM 2-3 times. Ensure fuel pressure does not drop when engine returns to idle. Check for fuel pressure in fuel return hose by gently pinching hose while raising engine speed. There will not be any fuel pressure in return hose if fuel volume is low.
- Stop engine and check for change in fuel pressure. Fuel pressure should not drop. If fuel pressure drops slowly after engine is stopped, replace fuel injector. If fuel pressure drops immediately after engine is stopped, replace fuel pump.
- If fuel pressure is too low during test, go to next step. If fuel pressure is too high, go to step 10). If fuel pressure is the same when fuel pressure regulator vacuum hose is connected and disconnected, go to step 11).
- Check for clogged fuel filter, faulty fuel pressure regulator or faulty fuel pump.
- Check for bent or clogged fuel return hose (pipe) or faulty fuel pressure regulator.
- Check for clogged or broken fuel pressure regulator vacuum hose or faulty fuel pressure regulator.