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Home >> GMC >> 1999 >> Forward Control 7.4 B >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Diagnostic Procedures >> Basic Fuel System Checks (Diesel Engines) >> Fuel Pump Flow Test
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Fuel Pump Flow Test

  1. Remove fuse for fuel pump circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Disconnect fuel line at fuel pump outlet fitting. Install a hose at fuel pump outlet fitting and place hose in a container to collect fuel.
  2. Crank engine for 15 seconds. If fuel pump does not supply about a 1/2 pint of fuel in 15 seconds, go to FUEL SYSTEM PRESSURE TEST .