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HOMESERVICE MANUALSCHEVROLET1985ASTRO VAN PASSENGER, 2.5 E, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEM2.5L TBI TESTS W/CODESDIAGNOSIS & TESTINGCHART A5 - FUEL SYSTEM DIAGNOSIS (1 OF 3)
1985 Chevrolet Astro Van Passenger, 2.5 E, Automatic

Chart A5 - Fuel System Diagnosis (1 Of 3)

1985 Chevrolet Astro Van Passenger, 2.5 E, AutomaticSECTION Chart A5 - Fuel System Diagnosis (1 Of 3)

When ignition switch is turned to "ON" position, the ECM will turn the in-tank fuel pump on. Pump will remain on as long as engine is cranking or running, and the ECM is receiving HEI distributor reference pulses.

If there are no reference pulses, ECM will shut off fuel pump within 2 seconds after key is turned on.

Fuel pressure at TBI unit is controlled at 9-13 lbs. Excess fuel is returned to fuel tank.

Fuel pump test terminal is located in ALCL connector terminal "G". When engine is stopped, pump can be turned on by applying battery voltage to 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, or hesitation.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).
  1. If fuse is blown, test confirms short to ground on circuit 120. Be sure fuel pump is disconnected before test.
  2. Determines if pump circuit is ECM controlled. ECM turns pump relay on, then off within 2 seconds since engine is not cranking or running.
  3. Fuel pump on if circuit 120 wiring is OK. If pump runs, it is a basic fuel delivery problem which the following steps will locate.
  4. Checks for battery voltage at pump relay.
  5. Checks relay ground circuit 450.
Fig 1: Chart A5 Schematic, Fuel System Diagnosis
G201378
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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.