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Thread: This was Interesting

  1. #1
    Registered Member scorpion1110's Avatar
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    This was Interesting

    So I am working on the 55 handyman.

    I have been putting in a new wire harness but also cleaning stuff up that bugged me and was related to initial start and break in.

    Today I wanted to clean up the fuel lines. Previously the 5/16th hard line ended and ran into a clear fuel filter, which ran into the mechanical pump. The pump fed into another filter which in turn ran the dual feed lines to the carbs.

    I posted a while back about the car being hard to start and possibly running an auxilary fuel pump. Rather than that I decided to add a check valve at the carbs right before the pressure gauge with a 40 micron fuel filter just before the pump. The clear filter was just for a visual when we set up the motor; I wanted to insure against any crud that came out of the tank, even though I flushed it, and I wanted to see when I had fuel to the pump.

    So I open the lines at the carbs and they are dry. I install a Russell check valve with AN6 fittings at the carbs feed line.

    Then to the main line. I decided to just cut the rubber line at the filter, and then was going to dump the fuel filter into a jar- the filter was full.

    So I opened the line and...

    The fuel disappeared. It was sucked out of the filter as soon as I opened the lines before the pump. Ok, so there was a vacuum pull towards the tank? It wasnt gravity because it was gone in a sec. Not sure what was going on, but I suspect this was impacting my fuel delivery issue.

    I shortened the hard line and inserted an Earls filter and then to the pump. I thought of a second check valve before the pump but decided against it.

    The motor isnt ready to start up yet, as I am not done with the motor wiring.

    It just seems odd that the filter was pulled dry immediately, and by the way when I opened the rubber line, it was empty as well.

    Thoughts?

    Scorp
    Last edited by scorpion1110; 09-15-2019 at 07:52 AM. Reason: spelling typo
    Scorp

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  2. #2
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    I can't speculate about your "vacuum" situation. However, I would not put a check valve in the line from the tank to the pump, and I wouldn't put anything finer than a 100 micron filter which is pretty coarse. Both the check valve and the filter are too much restriction for a suction line.

  3. #3
    Registered Member WagonCrazy's Avatar
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    2 filters + a check vave in the line + another filter just before the carb

    You have a restriction in the line somewhere. My bet is it's filter related. Pull them all out and plumb it without any filter (temporarily) to see if the problem goes away.
    Then put 1 NEW filter in before your fuel pump somewhere and you're good to go.
    Put a "serviceable" filter in...one that you can quickly pull out, open up, flush clean, reassemble, re=install....
    1957 Nomad- LS1/T56 on C4 chassis
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  4. #4
    Registered Member scorpion1110's Avatar
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    Thanks Rick-

    So there was likely suction still holding from the pump, which broke when I cut the line and the fuel pulled back. It was quicker than I expected.

    So do you really think the 35-40 Micron before the pump is a problem for general street use? What you are saying is the current thought pattern, 100 microns before pump, minimum 35 after and 10 if you have FI. My friend who is an old racer said that the 40 micron before the pump wont impact it for street use. If its a real issue, I want to pull it apart before I button up the passenger side because I can get to everything.

    The check valve is right before the pressure gauge and at the end of the feed from the pump.

    Ideally I would like to leave it alone, and save some $$$ and time, but will pull it back apart if its going to cause me headaches.

    Scorp
    Last edited by scorpion1110; 09-15-2019 at 07:50 AM. Reason: cant spell for crap
    Scorp

    Rides:

    1955 Chevy 2-door Wagon
    1967 MGB GT
    1970 Honda Trail 70
    1974 Yamaha 175 Enduro
    2004 Tacoma 4x4

    I lost my best friend on 10/3/2018. Rest in Peace Dear Lucy. I miss you everyday.

  5. #5
    Registered Member chevynut's Avatar
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    Do you have a vented cap on your fuel tank? These tanks aren't vented and they need to have a vented cap or you can create a vacuum in the tank from pump suction or temperature changes.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

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    Other vehicles:

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  6. #6
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    55 and 56 do not use a vented cap. Instead, there are 2 notches in the cap seat that allow ventilation.

  7. #7
    Registered Member BamaNomad's Avatar
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    Quote Originally Posted by Rick_L View Post
    55 and 56 do not use a vented cap. Instead, there are 2 notches in the cap seat that allow ventilation.
    Hmmm... Now THAT is great information... Thanks Rick..

    note. And if the tank has been replaced, especially with a custom one, the two notches *may* not be there, which would require a vented cap!

  8. #8
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    The filler pipe is the one with the cap seat and notches in it, it is a separate piece and usually would be re-used when replacing the tank. They are available repro though, and I think those have the notches just like the originals.

  9. #9
    Registered Member chevynut's Avatar
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    The point is......check and make sure the tank is getting vented. My filler neck has this notch in it. It's not hard to imagine that it could get plugged with a soft cap gasket, dirt buildup, or whatever.

    20070220_074.JPG
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax

  10. #10
    Registered Member chevynut's Avatar
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    I don't understand why you would need a check valve after the mechanical pump. Isn't the outlet valve of the pump essentially a check valve? If fuel is draining back, it seems to me that the pump outlet check valve must be leaking.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax

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