Results 1 to 11 of 11
  1. #1
    Join Date
    Aug 2004
    Location
    Red Deer, Alberta, Canada
    Posts
    1,237
    Country Flag: Canada

    External sump to solve starving problems

    So I'm currently deciding on what way I'm gonna go with fueling my 6.0l. I can get fab work done for a decent price so I could get my factory tank baffled and have a intank pump unit retrofitted in. Only problem with this way is I have no clue on how I should baffle the tank.(any ideas?)

    Now over on LS1tech theres a few of us guys talking about fuel tank mods. I'll just quote what he said.
    The rock-crawler cars with fuel injection sometimes use an external sump fed by a Delco/Carter high GPH low pressure pump, then plumb the bottom of the external sump to the high pressure fuel pump and the return to the top of the external fuel sump. At the top of the tank is a return line to the main tank, so the sump is always full.

    I did the same thing on my car and my external pump is about a quart of fuel and made from a piece of aluminum pipe about 5" in diameter and a $65 low pressure boost pump from Summit. Short of rolling the car, the suction side of the fuel injection pump is always in fuel (don't ask how I know this)
    It sounds overkill but maybe again its not? I think my first way to attack the fuel tank is the more suited route for me.

    -Matt

    Matt
    72 Chevelle 370ci LS Turbo. Speedtech equipped.


  2. #2
    Join Date
    Aug 2004
    Posts
    583
    It's not a bad idea, just more components that you have to try and fit in your vehicle.

  3. #3
    Join Date
    Nov 2002
    Location
    state of confusion
    Posts
    1,499
    Country Flag: United States
    Mostly that's what I did with my '79 when I moved up to EFI, and didn't want to modify a 20 year old fuel tank that was otherwise functioning perfectly well. I also added a large filter and a regulator, and fitted the little tank (I fabbed mine from stainless) with a Holley carb float bowl in order to have control over the fuel level. In normal street driving, I can run the 18.1 gallon tank down to under 1.5 gallons without getting a stumble, though autocross needs there to be somewhat more than 3 gallons. All those pumps, the tank, the low pressure filter, and the regulator fit in the spare tire well, which got covered.

    Norm
    '08 GT coupe, 5M, suspension unstockish (the occasional track toy)
    '19 WRX, Turbo-H4/6M (the family sedan . . . seriously)
    Gone but not forgotten dep't:
    '01 Maxima 20AE 5M, '10 LGT 6M, '95 626, V6/5M; '79 Malibu, V8/4M-5M; '87 Maxima, V6/5M; '72 Pinto, I4/4M; '64 Dodge V8/3A

  4. #4
    Join Date
    Nov 2004
    Location
    Colorado
    Posts
    1,323
    Country Flag: United States
    I forget which boat company it is, but they use what they call a Fuel Control Canister. Its a big filter, and a small tank with the pump mounted inside. The block mounted fuel pump keeps the FCC full, and the pump is cooled and kept wet this way. I tried this on my car, and the problem is getting the air out of the system. In addition things start to look like Rube Goldberg inventions after a while.

    I am going to cut an access panel into a new tank for my EFI 69, and install the pump in the tank, along with baffles and fuel cell foam.
    I have found a source for Viton rubber sheets, perfect for a gasket for the panel.

  5. #5
    Join Date
    Sep 2004
    Location
    Kettering, OH
    Posts
    537
    I've been curious to know why someone hasn't tried this option:

    Tanks Inc.

    John

  6. #6
    Join Date
    Aug 2004
    Location
    Red Deer, Alberta, Canada
    Posts
    1,237
    Country Flag: Canada
    Hammered. I'm looking at running that set-up with additional baffling. Right now when I go around corners with 3/4 tank I can watch my fuel gauge go from one extreme to the other.

    -Matt
    Matt
    72 Chevelle 370ci LS Turbo. Speedtech equipped.

  7. #7
    Join Date
    Aug 2004
    Location
    Milwaukee, Wi.
    Posts
    327
    Look into the airplane guys fuel systems, they do all kind of acrobatics and don't run out of fuel! I think they call it a redundant fuel system. Same idea as the rock crawlers, but maybe a little bit more sophisticated.

  8. #8
    Join Date
    Aug 2004
    Location
    Vancouver BC
    Posts
    189
    I think a good way to baffle a tank for a certain EFI setup is too have a look at the factory baffles in a tank that came from that vehicle. This way you know that the system will work well in cornering, braking , and acceleration.
    I'm going to have to check the dimensions to be sure but I think that, in my case, a steel 98 ls1 fuel tank is close (less than 1" difference)to the height of my 81 tank. I want to have the center section of the 98 tank grafted into my 81 tank, fuel pump and all. You may want to look for and match something up similar for your chevelle. I was quoted a round $250 for the fab work so all I need is a tank so I should be well under $500 all said and done.

    The Tanks.inc setup looks lke it should work well. I am debating going this route if plan a doesn't happen.

    BTW - I'm also doing a 6.0 swap. It's good to have others with similar projects as most people choose the aluminum block gen IIIs.

  9. #9
    Join Date
    Aug 2004
    Location
    absecon, new jersey
    Posts
    405
    Country Flag: United States
    73 corvette chop top silver LS6 motor ,LS6 intake,700r4,2400 pro torque convertor ,3.70 gears,modified hooker sidepipes to fit LS1,17 x9.5 boyd starburst,nitto 275/50/17-255/50/17 tires,vb&p suspension,nitrous,L-88 headlights,autometer guages.L88 hood,flares,spreader bar,vb&p sway bars

  10. #10
    Join Date
    Nov 2002
    Location
    state of confusion
    Posts
    1,499
    Country Flag: United States
    Quote Originally Posted by nitrovette
    Heres another idea
    I looked that page over and I think you should plumb the return line back to the main tank instead. My reasons involve heating of the fuel on each trip it takes through the engine compartment and fuel rails. From experience I know that this can, on a really hot day, vapor-lock an EFI pump that's not mounted internal to the surge tank (I'm not sure what the effect to an internally-mounted EFI pump might be). Best to dump it back into the large fuel volume and the greater tank surface area for rejecting this heat out to the atmosphere.

    And there is a possibility of increased return line backpressure affecting the fuel pressure in the rails if the return line has to compete with the lift pump in filling the sump. This would be more noticeable at idle, when the return flow is at its maximum and engine fuel requirements minimal, making the engine's tolerance for too much fuel the least.

    Norm
    '08 GT coupe, 5M, suspension unstockish (the occasional track toy)
    '19 WRX, Turbo-H4/6M (the family sedan . . . seriously)
    Gone but not forgotten dep't:
    '01 Maxima 20AE 5M, '10 LGT 6M, '95 626, V6/5M; '79 Malibu, V8/4M-5M; '87 Maxima, V6/5M; '72 Pinto, I4/4M; '64 Dodge V8/3A

  11. #11
    Join Date
    Feb 2005
    Posts
    13
    Nitrovette - Thanks for recommending my page, I'm glad to know someone may have found it useful.

    Norm - You're right, and that's basically what I did. I only used one of the extra ports I added to the external tank. One for input from the main tank, one for the output from the internal pump, and one for return to the main tank. I then teed the return from the engine into this return line just before the main tank. (If you read the webpage closely, in the Line Routing section, you'll see that I state the port for return line from the engine is optional, and that the engine return could go to the main tank, which is what I did. In hindsight, maybe I should change this to state the engine return should always go to the main tank and that the fourth port shouldn't be installed at all.)

    FYI -
    I've now had this setup in for a couple of years, (I think, lost track of time) without any problems. No leaks and no deterioration of the housing.

    This is a DIY for someone without the means to make a tank from scratch, as several of the guys above have done. Making a tank from scratch would be an even better option and give more sizing/mounting options. But this tank worked fine for me. (Almost too good actually - I was used to knowing when I was low on fuel by the engine stumbling around corners and when braking and accelerating. Now I have to watch the fuel gauge, because it doesn't stumble until it is bone dry.)

    I also thought along the lines of Zedzag recommendation of grafting part of a newer tank to my old tank. I decided to go this way because it was relatively quick and easy and I didn't have much time at the time.

    Ray