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Problem modifying factory to return style fuel setup

This is a discussion on Problem modifying factory to return style fuel setup within the General Help forums, part of the LSx Technical Help Section category; I finally finished my return style setup a couple weeks ago. Basically, it goes like this: From the factory fuel ...

  1. #1
    Junior Member scauffiel's Avatar
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    Problem modifying factory to return style fuel setup

    I finally finished my return style setup a couple weeks ago. Basically, it goes like this:

    From the factory fuel tank where I have a Walbro installed, to a surge tank via -6 teflon line.

    From the surge tank, through a Bosch 044 pump, to the engine compartment via -8 teflon line.

    In the engine compartment, it splits via a Y fitting to two -8 lines, one going to the back of each fuel rail.

    At the front of the rails, I bring the two together into a regulator via -6 fittings/line, and take the regulator's single -6 return line back to the factory hard line.

    Back at the rear of the car again, the factory hard line, now the return line, joins up at a Y fitting with the surge tank return line to go back to the fuel tank via -8 line.

    Here's a picture of the setup at the engine compartment:





    Here's the Y in the engine compartment where the supply line splits to each fuel rail: (the driver's side fuel line isn't installed here)





    Here's the external pump on the surge tank:





    And here you can see the Y fitting that takes the return fuel from the factory hard line and the excess fuel from the surge tank, and goes back to the factory fuel tank:







    Now, after all THAT, here's the problem. I drove her down to get the State Inspection done. On the way THERE I heard a weird moan as I was coming to a stop, but couldn't tell if it was coming from my car or the truck next to me, so I shrugged it off. When I left the place, I heard it again, a weird moan/low screech as I came to a stop at a light; it was coming from the right rear area. So now I'm thinking brakes, but as I'm driving home on the highway it happens occasionally while cruising - that takes the brakes out of the equation. Come off the highway, and it happens again as I slow down - I notice some fluctuation in my fuel pressure when it happens - and... hold on a tick, my external fuel pump is in the right rear too.

    I think, "Okay, maybe it's my supply hose pinched between something...." Pulled into the garage and now it's a constant noise and it's definitely coming from my external fuel pump - back up on ramps she goes. The supply line isn't pinched anywhere, but it definitely makes a racket that it's never made before, kind of a constant low screech with occasional stuttering.

    Thoughts? It puts out a fairly steady 62ish, nothing dying there. The external pump and exhaust while running is so loud I can't hear my in-tank pump, but I'd think if THAT wasn't putting out (and the surge tank was running dry) then the fuel pressure would be whack at least, and the car would stumble and try to die at worst.

    I bought another 044 (needed a standby replacement anyway if that's not the problem) and swapped it in last night. After draining the surge tank during the install - which tells me the in-tank Walbro is keeping it full - and reinstalling the new one, it does the same thing after about five minutes of idling.

    Now, the only thing I noticed last night when under the rear end was the large black plastic tube that runs from the evap canister underneath to the fuel tank at the top seems a little loose where it goes through the floor where it's still inside the black cover, but I can't tell if it's disconnected. Could it have become disconnected just up inside the black plastic fuel tank cover? Does it even come apart in that area? What symptoms would a problem with that cause? Before I rip everything apart to even SEE if there's any issues there...

    If you read this far and have any ideas, I'd appreciate any help or thoughts,

    Steve

  2. #2
    cutting and welding mark21742's Avatar
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    I'd check the evap hose to make sure its on good and no holes/ cracks in it. Also do you still have the plug and back line hooked up to the solenoid that layed on the drivers side of the intake manifold from the factory?

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    Junior Member scauffiel's Avatar
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    Quote Originally Posted by mark21742 View Post
    I'd check the evap hose to make sure its on good and no holes/ cracks in it. Also do you still have the plug and back line hooked up to the solenoid that layed on the drivers side of the intake manifold from the factory?
    Yep, everything there is hooked up and good to go. I'll take a look again at the evap stuff but after talking it out with some members of the club I think it's the Bosch sucking the surge tank dry. Before the mod the regulator returned the excess fuel right there to the surge tank; after the mod I've returned it to the factory fuel tank. I'd THINK the Walbro would keep it full, but maybe not. Should be an easy test to check it out...

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    Junior Member scauffiel's Avatar
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    Okay - Took the return to the surge tank instead of taking it back to the fuel tank and it no longer makes the noises. Looks like the Bosch overpowers the Walbro handily.

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    cutting and welding mark21742's Avatar
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    Quote Originally Posted by scauffiel View Post
    Okay - Took the return to the surge tank instead of taking it back to the fuel tank and it no longer makes the noises. Looks like the Bosch overpowers the Walbro handily.
    Ok good! Could you just put on a free flow line from the surge tank back into the main tank so your not pressurizing the surge tank, or do you want it pressurized?

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    Junior Member scauffiel's Avatar
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    Quote Originally Posted by mark21742 View Post
    Ok good! Could you just put on a free flow line from the surge tank back into the main tank so your not pressurizing the surge tank, or do you want it pressurized?
    Yep, the line to take overflow from the surge to the main fuel tank was already there.

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    Moderator Cutlass's Avatar
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    Make sure the in tank pump is actually working and that the fuel filter isn't clogged. Those 2 things can make your inline pump work harder and create noise.

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