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Fuel pump diagnostics for internal combustion engine

  • US 4,094,191 A
  • Filed: 03/25/1977
  • Issued: 06/13/1978
  • Est. Priority Date: 03/25/1977
  • Status: Expired due to Term
First Claim
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1. In a method of diagnosing an engine fuel system of the type having a fuel pressure-regulating bypass valve, which is normally closed to provide fuel at full pump pressure at low speeds, and opens proportionally to bypass fuel to limit the pressure thereof at higher speeds, the steps of:

  • operating the engine at substantially a low idle speed and at substantially a high idle speed;

    at each of said speeds, measuring the pressure of fuel provided to the bypass valve by a pump; and

    providing a manifestation of the fact that the bypass valve is stuck in the open position if the pressure measured at said high idle speed is substantially the normal rated high idle speed fuel pressure for the engine under test and the pressure measured at said low idle speed is lower than the normal rated low idle speed fuel pressure for the engine under test.

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