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Please Help!! No one can seem to give me a solid answer

Discussion in 'The Garage' started by coopdog, Apr 10, 2006.

  1. coopdog

    coopdog Registered Member

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    72 Chevy Truck, BB 454, tank is behind the seat

    I am replacing my mechanical fuel pump with an Edelbrock electric fuel pump part # 1791. The Edelbrock technician said to mount the new pump below the tank on or near the frame...no problem. However, when I removed my mechanical fuel pump I noticed that there were two fuel lines...a 3/8" line and a 1/4" line. The Edelbrock tech said the 3/8" line is the main fuel line and that it should go/hook up to the electric fuel pump….NO PROBLEM! But what do I do with that 1/4" line…it runs from the tank to the engine compartment…I was told it was a return line for the old mechanical fuel pump….I have a bolt with a hose clamp on the end of it.

    Can I just remove this line altogether???
     
  2. justhorsinaround

    justhorsinaround 3/4 ton status

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    My gut says yes. On the condition however that your float bowl needle and seat are in good condition.

    I've run several motors with no returns and electric fuel pumps with no issues.
     
  3. coopdog

    coopdog Registered Member

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    Ok..just so I understand...Its alright to remove the return line and just cap it off under the tank. The carb is brand new so should have a problem there. This wont hurt my gas mileage will it??

    Thank you for the response

    Semper Fi

    Coopdog
     
  4. justhorsinaround

    justhorsinaround 3/4 ton status

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    Nope all the return is/was (from what I understand) for bleeding off the pressure the fuel pump kept wanting to push into the bowl. Now then if you have a new carbuerator I wouldn't sweat it.

    I could be wrong, but as I said I've run many a vehicle with no return line with no issues.
     
  5. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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  6. coopdog

    coopdog Registered Member

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    After reading the above link I am not a 100% certain that the 3/8" line is the main fuel line and the 1/4" line is the return line. Is there some way to be certain which is which?

    Thanks Coopdog
     
  7. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    The 3/8" line is the fuel supply line and the 1/4" line IIRC went to your charchoal canister and is a vent line. Take the 1/4" line and mount it so that it is higher than the top of the fuel tank and place a 1/4" fuel filter on this line so it can still vent the tank properly. I have seen people just plug the line and be ok, but i've also seen people plug the line and have the fuel tank implode (suck in).
     
  8. coopdog

    coopdog Registered Member

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    Ok...makes more sense now...but my tank is behind the seat of my truck and if I am to mount the filter (so the tank can vent properly) above the tank...it will be inside the cab of the truck and smell like fuel obviously...or I coumld mount the line to the outside top of the cab which would look like crap. If I mount the line and filter below the tank it will obviously leak. It makes sense that If I just cap it off it could cause the tank to implode. Still stumped on what to do with that darn line. Any other sugestions. And thanks for the help.

    Semper Fi

    Coopdog
     
  9. R77K10

    R77K10 Banned

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    3/8 will be the main feed size if its a factory 4bbl truck

    Ie not a 6 cyl or 2bbl truck

    otherwise it will be 5/16" main, including the sender unit too,

    restrictive

    why are you going to electric when mechnical always works fine ?

    that is alot of work for no real gain

    is there a problem you have been having with the truck that is making you want to go to electric ?

    youre gonna have to knock the presure down to 7 to 9 psi or youll have a real big problem,

    the 1/4" is the return line

    it connected to the unit in the cab corner up high passenger side, or went up front to charcoal canister possibly, if i had one at all originally

    most of the 71 and 72 had the unit in the cab corner inside the double wall area by the tank, on passenger side and but not all did, only certain series did, i cant remember if it ws only in the 1/2 tons or if it was only in the 3/4 and 1 tons

    i forgot now

    but i knwo it was only in 71 and 72



    4x4high knows whats goin on



    good luck
     
    Last edited: Apr 13, 2006
  10. coopdog

    coopdog Registered Member

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    Wow..thanks for the response..thats been the most informative yet. And yes there there is a line that runs up inside the double wall of the cab and then up to the engine compartment.

    The reason for the the electric fuel pump is that the motor is s trun key engine and did not come with a mechanical fuel pump. The builders of the engine said that this motor would preform better with the Edelbrock 1791 electric fuel pump that they provided. They said the pump is set at 6.5 lbs of pressure and to not mess with it. They had no advice as what to do with the 1/4" return/vapor line. Three more questions for ya please.....

    Can I remove the 1/4 return line (the portion that runs up to the engine compartment) and cap it off under the truck?

    Do I need a fuel filter before the fuel pump? (already one at the carb)

    Can I replace the metal 3/8 fuel line with a rubber one? (reason is the metal one is badly bent and runs right next/on top of my headers...the rubber line would allow me to run it next to the frame)

    Thank you so much for the help!

    Semper Fi

    Coopdog
     

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