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Thread: Can't Shake a Lean Condition - HELP

  1. #41
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    MAF looks good. Voltage and wiring looks correct as well.

    Wondering if I have a fuel pressure issue. . I turn the key on. It primes to ~40 psi, and then the pump turns off. Within 1-2 seconds, the fuel level goes to ~20 psi, and to zero within 7-8 seconds. Assuming this isn’t normal from other post I have read on NASOIC. I had in my head there was an drain back valve. If yes, is this s on the pump stock in the tank?

  2. #42
    Senior Member alpine227's Avatar
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    If you have to open the throttle to start, sounds like it's too rich. Can you adjust cranking pulse widths?

  3. #43
    Senior Member Bob_n_Cincy's Avatar
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    Quote Originally Posted by mrbiglar View Post
    MAF looks good. Voltage and wiring looks correct as well.

    Wondering if I have a fuel pressure issue. . I turn the key on. It primes to ~40 psi, and then the pump turns off. Within 1-2 seconds, the fuel level goes to ~20 psi, and to zero within 7-8 seconds. Assuming this isn’t normal from other post I have read on NASOIC. I had in my head there was an drain back valve. If yes, is this s on the pump stock in the tank?
    There are 3 condition that the full pump should be running.
    1. for a few second after ignition is turned on.
    2. while cranking the starter.
    3. while engine is running.

    The fuel pressure dropping to zero in 7-8 seconds indicates to me a problem in the fuel system.
    I would expect it to hold pressure for minutes or even hours.
    1. bad check valve in the fuel pump (in tank).
    2. bad valve in the fuel pressure regulator (normally under intake manifold).
    3. leaking fuel injector.
    4. leak somewhere between pump and FPR.

    Bob

    EDIT: your Perrin aftermarket FPR is bolted on top the intake.
    Last edited by Bob_n_Cincy; 09-24-2017 at 12:10 PM.
    818S #22 Candy Blue Frame, Front Gas Tank, 2.5L Turbo, Rear radiator, Shortened Transmission, Wookiee Compatible, Console mounted MR2 Shifter, Custom ECU panel, AWIC soon
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  4. #44
    Senior Member flynntuna's Avatar
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    Just to add to what Bob said, a leaking fuel injector could lead to fuel in the oil, very bad. But a leaking injector should make starting warm a little more difficult right? Behaving like a flooded condition?

  5. #45
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    Pretty sure I have a bad check valve on the fuel pump. Put Subaru OEM FPR on and it still wouldn't hold. New pump on the way...

    Thanks for insight. Will let you know how it turns out.

  6. #46
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    Bad Check Valve on the pump. Swapped for a DW300 (much quieter than the Wahlbro). Started right up. Thanks all for the help!

  7. #47
    Senior Member alpine227's Avatar
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    Yes they are, Glade your up and running!

  8. #48
    Senior Member AZPete's Avatar
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    Whew, finally after 5 months! I've been following this all along not because I could help, but to learn what could cause the lean condition. Congrats, Mrbiglar, and thanks for the lessons.
    818S/C : Chassis #25 with 06 WRX 2.5 turbo, ABS, cruise, PS, A/C, Apple CarPlay, rear camera, power windows & locks, leather & other complexities. Sold 10/19 with 5,800 miles.
    Mk3 Roadster #6228 4.6L, T45, IRS, PS, PB, ABS, Cruise, Koni's, 17" Halibrands, red w/ silver - 9K miles then sold @ Barrett-Jackson Jan 2011 (got back cash spent).

  9. #49
    Senior Member fletch's Avatar
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    Quote Originally Posted by Bob_n_Cincy View Post
    Mrbiglar,
    Per the schematic below your pin 3 & 4 are backwards. Black wire should be on pin 3 and white wire should be on pin 4 of the sensor.
    I had the same issue as the OP -persistent too lean, AFR & AF Correction pegged at max values. Double checked everything, swapped O2 sensors, etc. After reading this post I decided it was worth a try swapping sensor + and - to see if the condition would reverse. In fact, the pin swap fixed the problem. Turns out the 2006 FSM has sensor + and - swapped.

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