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Thread: Fuel pressure woes

  1. #1
    Senior Member whitey's Avatar
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    Fuel pressure woes

    Well, heres the problem, and im trying to find a solution...

    Fuel pressure at idle is 37 to 40 psi.

    Fuel pressure at WOT was at 12psi according to my scanguage, AF was around 13.4(autometer wideband gauge). I replaced the fuel pump today, with a new aeromotive 340. Fuel pressure at WOT now reads around 24psi according to my scangauge, AF was around 12.4. I swapped my FPDM with another unit, same results. I have 10g wire coming from my battery, to a 30/40A relay, that feeds my FPDM with verified 14.2volts. Stock wires from FPDM to the pump. Its the stock returnless style fuel system.

    What am i missing here? Is the scangauge off in psi when reading the fuel pressure? If so, why am i running on the lean side at WOT? Previously(before all this was happening) i was running a ~11.5 AF at WOT. Thanks for reading, love, whitey.
    Last edited by whitey; 11-26-2017 at 07:18 PM.
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    Senior Member RubberCityRauder's Avatar
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    do you have a boost a pump?
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    whitey (11-26-2017)

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    Maraudering the globe Spectragod's Avatar
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    Fuel pressure is low, fuel filter, kinked fuel line etc.


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    whitey (11-26-2017)

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    Senior Member whitey's Avatar
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    No boost a pump.
    I will change the fuel filter soon. I changed it about 6k miles ago though with a motorcraft filter.
    --Confucius say: Man with itchy asshole, has stinky finger--

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    Maraudering the globe Spectragod's Avatar
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    Might have some trash in it, or..... you have something plugged up...


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    6 speed junkie justbob's Avatar
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    You should be seeing right around 40 at all times with a scan gauge/ OBD port set up as it reads delta pressure and not actual fuel pressure.

    Assuming you originally had good pressure and you changed your pump and saw an increase, I️ would almost bank on a bad pump out of the box, or leaking at the hose connection to the pump since the hose supplied is to big for the nipple to begin with plus wrong clamps supplied..

    Unless youíve pumped some seriously bad gas, I️ highly doubt your filter is bad. I️ bet I️ go 30-40,000 Miles in between cleaning/changing filters and they are always fine.

    Or for giggles hook up a fuel pressure gauge and look for an additional pound or so for each pound of boost added to the original 40.


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    whitey (11-29-2017)

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    Maraudering the globe Spectragod's Avatar
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    Quote Originally Posted by justbob View Post
    You should be seeing right around 40 at all times with a scan gauge/ OBD port set up as it reads delta pressure and not actual fuel pressure.

    Assuming you originally had good pressure and you changed your pump and saw an increase, I️ would almost bank on a bad pump out of the box, or leaking at the hose connection to the pump since the hose supplied is to big for the nipple to begin with plus wrong clamps supplied..

    Unless youíve pumped some seriously bad gas, I️ highly doubt your filter is bad. I️ bet I️ go 30-40,000 Miles in between cleaning/changing filters and they are always fine.

    Or for giggles hook up a fuel pressure gauge and look for an additional pound or so for each pound of boost added to the original 40.


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    And this above is why I have a mechanical fuel pressure gauge.

    I didnít factor in a bad pump or loose hose since you had been into it and changed the pump out. It is plausible, and with the amount of defective parts rolling out into mainstream sales, I would say it is possible.

    I kinda got a little lost when Bob started talking about nipples......hmmmm



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    You can go a long way with a smile, You can go a lot further with a smile and a gun.

    Boost gets you felony stopped!!!

    When you are dead, you donít know you are dead. It is difficult only for others. It is the same way when you are stupid.


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    Senior Member musclemerc's Avatar
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    it may be time to consider a full dual setup

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    Intercept THIS tbone's Avatar
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    Boost a pump and Aeromotive 340 are not recommended to be used simultaneously.

    WARNING (AMPERAGE)

    The Walbro and Aeromotive pumps used in either single or dual applications obviously produce more flow than stock pumps – BUT AMPERAGE IS MUCH HIGHER. Example: Up to 73% 14.2-17.2 vs 9.9 amps (Walbro GSS340). Therefore, the stock wiring system is incapable of handling the increased loads and must be upgraded or replaced. This higher pump amperage negates using the BOOST-A-PUMP™ and it’s 17.5-21V advantage. The BOOST-A-PUMP™ is not designed to operate these high amp aftermarket pumps. Check out the flow numbers and cost of the 2 approaches. You will see that it is difficult to beat the cost of a Kenne Bell BOOST-A-PUMPģ/Stock Pump combination for the overwhelming majority of applications.
    Last edited by tbone; 11-27-2017 at 03:38 PM.

  14. #10
    Senior Member musclemerc's Avatar
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    ^^^ This is true....

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