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Scot

Scot 10/16/2017

2000 Mercury Sable LS 6 Cyl 3.00L

Engine

How do you find a fuel pressure leak? Engine is a 6 cyl. 3.0L not the 2.6. Web sight wouldn't let me change engine size.

I had the engine replaced which is 6 Cyl 30 . Used all of the fuel delivery system from old engine. Had a small miss. Changed fuel injector and coil on cyl that had miss. Thought I had that taken care of. Still had small miss. I put fuel pressure gauge on fuel line. Turn key on pressure jump up to about 38 lbs. pressure and immediately the pressure drops off to about 10. (Car will start) I have not seen any fuel leaking out onto the ground. I checked oil, no fuel in oil.

1 Answer


HouseCallAuto

HouseCallAuto 10/16/2017

The pressure drop is likely a bad fuel pump leaking internally, however, there is a fuel pressure regulator located on the fuel rail of the engine which if bad can cause low fuel pressure but they rarely fail. The way to confirm whether the pump is bad or the regulator would be to restrict the return line (which may require special adaptors) in simple terms to convey the diagnostic strategy here....collapse closed the return fuel line while measuring fuel pressure. If it still drops to 10psi, then the pump is the cause, if the pressure shoots up way high like 50psi or higher, then the regulator is bad.

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