Low Pressure Fuel Pump Test

1985 Ford Econoline E350, Van Display Extended, 5.8 GSECTION Low Pressure Fuel Pump Test
  1. Open fuel line at high pressure pump inlet. Connect hose to line from fuel tank. Route hose to a 1 quart, calibrated container. Disconnect high pressure fuel pump electrical connector from body wiring harness.
  2. Replace fuel pump relay with modified relay. Refer to MODIFYING FUEL CUT-OFF RELAYΒ  in this article. Ground wire coming from relay to a convenient ground point to energize fuel pump and measure flow for 10 seconds.
    NOTE: It may be necessary to momentarily block fuel hose to prime low pressure pump with outlet open and no back pressure on outlet; this is normal.
  3. If fuel pump produces a minimum flow of 16 oz. of fuel in 10 seconds, pump is operating correctly. If there is no flow from pump, check electrical circuit, and also for inlet line restriction. Replace pump if required.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.