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Thread: Fuel system electrical - stupid design

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    Better than that "other" place Not Verified Feedback Score 2 (100%) x2xtreme360's Avatar
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    Fuel system electrical - stupid design

    WHY... doesn't our fuel pump prime? Almost every car I've seen has a fuel pump that primes in the ON position, yet ours doesn't. Even my fuels professor was surprised when I told him it doesn't.

    I have a fuel pressure drop off issue that I haven't been able to pinpoint yet. The pressure drops off VERY quickly after the car is turned off, and then it takes 5 or more seconds to get it fired back up due to no fuel pressure in the rails. I KNOW it's taking a toll on my starter.

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    Forum User Feedback Score 0 Beef6's Avatar
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    Do you have an afpr?

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    My Truck is Faster Than My Car Feedback Score 0 lparrill's Avatar
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    Quote Originally Posted by x2xtreme360 View Post
    WHY... doesn't our fuel pump prime? Almost every car I've seen has a fuel pump that primes in the ON position, yet ours doesn't. Even my fuels professor was surprised when I told him it doesn't.

    I have a fuel pressure drop off issue that I haven't been able to pinpoint yet. The pressure drops off VERY quickly after the car is turned off, and then it takes 5 or more seconds to get it fired back up due to no fuel pressure in the rails. I KNOW it's taking a toll on my starter.
    I'm having the SAME exact problem. I can't figure it out, I swapped in two different sets of injectors, the latest set with brand new o rings and still the same problem. I don't even know how to test to find a leak.

    And yes, I have an AEM FPR.
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    Forum User Not Verified Feedback Score 2 (100%) RealMcCoy's Avatar
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    That's a common issue with aftermarket AFPR's... The stock Denso pump with the stock FPR was very well sealed up, and priming was not necessary.

    It would not be that difficult to wire in a timed fuel pump relay from another type of car.

    Personally I'd be looking for a regulator that doesn't leak...


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    Member Not Verified Feedback Score 7 (100%) mb3000's Avatar
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    My Paxton seems to be above the norm, holding some pressure for about 12 hours.

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    Doesnt sound like a design issue but more a maintenance issue. Where is the pressure leaking out to? My guess is fuel pump.

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    Twin Turbo verified Feedback Score 5 (100%) GTOJOE's Avatar
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    Quote Originally Posted by x2xtreme360 View Post
    WHY... doesn't our fuel pump prime? Almost every car I've seen has a fuel pump that primes in the ON position, yet ours doesn't. Even my fuels professor was surprised when I told him it doesn't.

    I have a fuel pressure drop off issue that I haven't been able to pinpoint yet. The pressure drops off VERY quickly after the car is turned off, and then it takes 5 or more seconds to get it fired back up due to no fuel pressure in the rails. I KNOW it's taking a toll on my starter.
    Mine does [maybe a JDM thing]. I can hear the pump running when in the ON possition. The only mod to this system so far is the resistor bypass. My stock FPR sems to loose pressure after 2 days. If I start the car the next day it's fine. Starts perfect. After the 2nd day it starts but not as well. 3rd day it basically won't start lol. Park my car on friday night monday it won't start until I prime it and try twice. Hopefully when I get around to installing the Fuelab it won't have that problem.
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    Better than that "other" place Not Verified Feedback Score 2 (100%) x2xtreme360's Avatar
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    I do have an AEM AFPR. The issue started as soon as I installed it over a year ago, but the issue got a LOT worse 4 days ago when I had to change out my sender. There's no leaks where I did the work though. Maintenance is fine on my setup. Stainless lines, ALL new Orings. Injector seals, zero leaks as far as I can tell.

    If it weren't for the stainless lines, I could kink one of the hoses on shutdown and figure out if the fuel is going back to the tank or through the FPR.

    When I removed my sender to my aftermarket gauge the other day (located by the filter), almost NO fuel came out of the port. Leading me to believe it's getting itself back to the tank somehow.

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    Forum User Feedback Score 0 Beef6's Avatar
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    Im pretty sure its a common thing for the afpr to bleed off the pressure. Mine is usually down to 0psi in about 2 hours. Not sure about it being worse after changing out the sending unit other than a leak.

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    My Truck is Faster Than My Car Feedback Score 0 lparrill's Avatar
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    My problem was the fuel pressure dropped almost instantly. Today I swapped out my AEM FPR for a OEM one and the problem is semi-solved. At least it will hold pressure so I can get the car started, but my hotwired walbro is overwhelming it.

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