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My OBD shows that I have low fuel pressure in a 1997 Ford Mercury (tracer). Do I have to replace the fuel pump? If so, do I have to replace the whole thing or is it enough to replace just the motor unit? What else might cause low fuel pressure reading?

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    I am not familiar with a code or a data output that measures fuel pressure on the OBD system. If it's a code what's the code, if not is it a data point that simply says low fuel pressure, or does it give a valve? Also please include the engine size in your question. – Move More Comments Link To Top Jul 31 '11 at 19:29
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Generally speaking (not familiar with that model), it could be due to:

  • Bad fuel pump (fairly rare, fuel pumps are one thing that usually last forever)
  • Clogged fuel filter (has it been changed recently/ever?)
  • Bad fuel pressure regulator (although, they usually fail the opposite way)
  • Leaking fuel injectors (unlikely, would require a pump that's marginal to begin with)
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    I'd change the fuel filter first, that one is often overlooked... – Timo Geusch Aug 2 '11 at 19:29
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The 97 Mercury Tracer doesn't use a Fuel Rail Pressure sensor and any reading you're getting from your OBD2 application is false.

If you believe that the fuel pressure is low, hook up a fuel pressure gauge and verify before replacing anything.

Refer to Brian Knoblauch's answer for potential causes.

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1997 Ford Escort wagon, my found issue. Ethanol caused rubber fuel hose to metal tube failures. Hose would swell in hot weather, or when engine heat concentrated enough to swell hose inward. Fuel pressure dropped so bad it would not start. replaced hose, never another issue.

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