NOTE: Test numbers refer to test numbers on diagnostic chart.

Use Pressure Gauge (J-34730-1) and Adapter (J-35957-10) . Wrap shop towel around fuel pressure fitting to absorb any fuel leakage when installing gauge. On correctly functioning system, fuel pressure will not leak down when ignition is off.
Manifold vacuum pressure is low when engine is idling. When vacuum is applied to fuel pressure regulator diaphragm, fuel pressure will drop to approximately 25-30 psi (1.8-2.1 kg/cm² ).
Applying vacuum to pressure regulator should cause fuel pressure to drop slightly.
Pressure leak-down may be caused by one of following:
- In-tank fuel pump check valve not holding
- Pump coupling hose leaking
- Fuel pressure regulator valve leaking
- Injector sticking open
Pressure less than 39 psi (2.7 kg/cm² ) may be caused by one of following:
- Regulated fuel pressure is too low. System will be running lean and may set Code 44. Hard cold starting and overall poor performance is possible.
- Restricted flow is causing a pressure drop. Vehicle with fuel pressure drop at idle usually not driveable. Fuel pressure drop while driving will cause engine surge and then stop as pressure rapidly drops.
Restricting fuel return line when battery voltage is applied to fuel pump, allows fuel pump to build over regulated pressure. Pressure should be 65 psi (4.5 kg/cm² ) or greater.
This determines if high fuel pressure is due to restricted fuel line or a pressure regulator problem.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Chart A-7, Fuel System Pressure Test (Turbo): Notes