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Thread: Salvaged - IMPORTANT: Check Your Fuel Pump Relay!

  1. #1
    Senior Member 98930EVO's Avatar
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    Salvaged - IMPORTANT: Check Your Fuel Pump Relay!

    Although the Evo X tuning community has known about this problem for years now, we want to put a friendly reminder out there to our forum-going Evo X owners to check your fuel pump relays. If your relay is a short black unit as pictured below and your car is a 2008-2010 model year, it is probably already bad. Regardless, you must absolutely replace the pictured relay if it's a short black unit.

    It is absolutely critical to replace the fuel pump relay as highlighted in the photo above. Since this relay controls the high-low voltage crossover of the fuel pump, having it go bad can cause the fuel pump to only run at low voltage instead of +12 V at WOT. Depending on your tune or chosen COBB Off-the-Shelf map - or factory tune - your car can run leaner than intended under full boost, anywhere from 11.5 AFR to 14 AFR. This is a definite recipe for a blown motor and something not even the best detonation/knock detection algorithm could prevent.

    Relay Reference

    Bad - if you have this short black relay in the position marked above you need to replace it.

    Good - if you have a green relay in the position marked above you're probably good.

    Better - the blue relay was the second recommended revision from Mitsubishi - OEM P/N 8627A024

    Best - this is the newest recommended OEM relay from Mitsubishi - OEM P/N MR122409

    * New Panasonic relay is available, more information to come if it's found to be an improvement or recommended by MMNA

    If you indeed have the short black relay (the "bad" one) you can quickly verify it has failed by pulling it out and giving it a shake. If it sounds like it's filled with sand, it's definitely bad.

    It should also be noted that Mitsubishi and other tuners recommend replacing a total of 5 relays in your engine bay fuse box. We also agree that this is a best practice, but the most critical relay to replace is the fuel pump relay as it's most prone to failure being the relay that experiences the most cycles during normal operation.

    More Reading

    A better way to check if the relay is bad:

    Here is a forum thread showing evidence of failure in the original black relay:

    Buy a full set of updated relays from Kozmic Motorsports:
    2014 PB MR Touring
    Life is too short to drive boring ass cars - Razorlab
    Because freedumb - Yxd68

  2. #2
    Senior Member redefined's Avatar
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    Thanks for this info, I didn't know! Just went out to check on mine and snapped a picture. Looks like I'll be sourcing a new relay - car is a 2012.

  3. #3
    Evo X Harlot UT_EvoX's Avatar
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    We still see defective relays out there, so just bumping this. We sell the latest orange relay on our website here:

    It includes some replacement hose for the FPR hose as well since zip ties or clamps alone can't repair crunchy and cracked hose (which is why they blow off).
    350 WHP WW Flex Fuel 2014 Evo X MR | 600 WHP OB 2008 Evo X GSR

    Evo X Builder & Tuner since 2009 - Boosted Mitsubishis since 2005 | Buy fuel kits, flex fuel setups, or order an e-tune online:

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