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HOMESERVICE MANUALSPONTIAC1984FIERO BASE, STANDARD, MY8REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSIS1.8L/2.5L/5.7L TBI TESTSCHART A5 - FUEL SYSTEM DIAGNOSIS (CORVETTE)
1984 Pontiac Fiero Base, Standard, MY8

Chart A5 - Fuel System Diagnosis (Corvette)

1984 Pontiac Fiero Base, Standard, MY8SECTION Chart A5 - Fuel System Diagnosis (Corvette)

The ECM turns on the in-tank fuel pump as long as the ignition is "ON" and the engine is cranking or running. The ECM will allow the pump to run as long as it receives reference pulses from the distributor. If there are no reference pulses, the ECM will shut off the fuel pump within 2 seconds after key "ON." The fuel pump test terminal is located in term. "G" of the ALDL. When the engine is stopped, the pump can be turned "ON" by applying battery voltage to the test terminal. Improper fuel system pressure will result in one or all of the following symptoms: Cranks but won't run, Code 44, Code 45, cuts out, may feel like ignition problem, poor fuel economy, loss of power, and hesitation.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).
  1. If the fuse is blown, this will confirm a short to ground on circuit 120. To prevent mis-diagnosis, be sure fuel pump is disconnected before test.
  2. This test determines if the pump circuit is ECM controlled. The ECM will turn on the pump relay, then turn it off after 2 seconds of the engine not cranking or running.
  3. This step turns on the fuel pump if circuit 120 wiring is good.
  4. This step checks for battery voltage at the pump relay.
  5. This step checks relay ground circuit 450.
Fig 1: Chart A5, Fuel System Diagnosis Flow Chart (Corvette)
G1347
RENDER: 1.0x

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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.