Bad Fuel Pump Symtoms & Diagnosis

Modified on Wed, 11 Jan, 2023 at 1:57 PM

ELECTRIC FUEL PUMP FAULTS

INSUFFICIENT FUEL

  • Air leak at intake side of pump
  • Air leak at diaphragm flange
  • Leaking valves
  • Perforated or faulty diaphragm
  • Vapor lock in fuel line
  • Faulty electrical feed
  • Bad ground
  • Contact points burnt
  • Corroded throw-over mechanism
  • Incorrectly adjusted throw-over mechanism
  • Excessive diaphragm tension
  • Blocked filter

PUMP BEATS RAPIDLY

  • Carburetor flooding
  • Air leak in suction line
  • Fuel leak
  • Vapor lock in fuel line


EXCESSIVE DELIVERY PRESSURE

  • Incorrect pump fitted


DOES NOT OPERATE

  • No electrical supply
  • Bad ground
  • Faulty coil winding
  • Faulty internal pump connection
  • Dirty contact points
  • Corroded or incorrectly adjusted throw-over mechanism
  • Diaphragm pressure excessive

MECHANICAL FUEL PUMP FAULTS

INSUFFICIENT FUEL

  • Air leak at filter bowl or suction side of pump
  • Air leak at diaphragm flange
  • Leaking valves
  • Blocked vent in gas tank
  • Perforated or hardened diaphragm
  • Worn or broken pump linkage
  • Blocked filter
  • Vapor lock in fuel line

EXCESSIVE DELIVERY PRESSURE

  • Carburetor needle valve seating improperly
  • Incorrect needle valve
  • Diaphragm faulty
  • Incorrect diaphragm spring
  • Pump mounting gasket too thin


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