5 - Fuel System LEAKDOWN Test

TOOLS REQUIRED:  SA9127E Gage Bar Set

The fuel system leakdown test will determine if the fuel system is able to hold fuel pressure when the fuel pump is not operating. The system must hold pressure to assure that the fuel supply circuit (fuel lines, filter/regulator, and fuel rail) is full of fuel. When the fuel supply is completely charged, fuel will be available at the injectors as soon as the ignition is turned on.

1. Remove air induction tube.
2. Relieve fuel system pressure. Refer to RELIEVING FUEL PRESSURE .
   Fig 1: Relieving Fuel System Pressure

   Courtesy of GENERAL MOTORS CORP.
3. Connect Gage Bar Set SA9127E to fuel pressure port.
   NOTE: Battery must be at a minimum of 12 volts when performing any fuel system test. Charge battery before proceeding if below 12 volts.
4. Energize fuel pump. Refer to ENERGIZING THE FUEL PUMP  for a minimum of 10 seconds.
   1. Record fuel pressure.
   2. Repeat this procedure a minimum of two times.
5. Shut fuel pump OFF and wait 5 minutes.
6. Record fuel pressure and subtract from pressure recorded in step  1.
7. Compare pressure loss (decay) to published specification.
   Fig 2: Fuel System Leakdown Test Table

   Courtesy of GENERAL MOTORS CORP.
8. Refer to FUEL SYSTEM DIAGNOSIS - FUEL SUPPLY CHART  and use test result to make appropriate decision.