Help with Vapor lock

Discussion in 'Troubleshooting & Diagnosis' started by dph42, Feb 27, 2018.

  1. dph42

    dph42 New Member

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    Feb 26, 2018
    Greetings gentlemen and thanks for adding me to your group! I am hoping you can help me with a couple of problems on two different cars that may actually be the same issue. I will start with my '70 since it is the most pressing due to the fact that I need to sell it due to some pressing financial issues due in part but not entirely to my recent medical problems.
    The car is a '70 model with the original motor and trans still in it. It is equipt with headers, an Edelbrock carb and intake. It had been sitting at my Son's place for 2 or 3 years with the stipulation he kept it running and driving. Well it sat. We drained the tank, replaced the fuel pump and fuel and I trailered it into town. To the point,the car starts fine, fills the filter, but will only run 10 to 20 minutes and the pump reaches between 120-130 degrees (depending on the outside temp) I can see the fuel start to boil in the filter until gone, much like a Youtube video I will try to post a link to. The fuel pump is a single line just like we pulled off, that the car ran great with for years. I have tried all kinds of things from looking for bad spots in the lines to trying with the cap off. Has anyone experienced this and do you have a good inexpensive solution. I have been told a return line will help but not sure how i would run it. The car still has its charcoal canister but all that stuff has been disconnected. Sorry for the long post but wanted to give you as much info as possible. Thanks in advance for your help! I will attempt to post the link. www.youtube.com/watch?v=cadNfSNi_Oc&t=64s
     
  2. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    Nov 4, 2004
    Ringgold, GA
    If you're seeing fuel percolate in the filter, before it gets to the carburetor, you most likely have the fuel line too close to a heat source. Is this a flex line with the filter attached, running from the pump to the carburetor? You might try a piece of heat sleeve in that area. I don't think a heat shield or isolator below the carb will help, since the fuel is perking before it gets to the carb. Years ago, with steel lines all the way to the carburetor, we put clothespins on the line as heat sinks. Don't know how much it helped but everyone did it. You could also have a fuel pump that's losing some efficiency.

    Welcome to NastyZ. :)
     
  3. dph42

    dph42 New Member

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    Feb 26, 2018
    Thanks for your response! And thanks for having me!. It is a rubber line from the pump to the filter and then to the carb. I am thinking it may be getting heated by the headers where the metal fuel line is close, mounted on the frame rail. I was reading where another member said he ran his lines underneath the upper control arm, I might look into that, but as I am needing to sell it I don't want to turn off a potential buyer. Other people have told me about the clothespins and said it worked. Just curious, were they just regular wooden ones? I really do not understand how the car always ran fine before even in the summer. I live in Central Texas and its not like our summers are very cool. I have other friends with similar set ups and say they never have any issues. I am stumped!
    Thanks,
    David
     
  4. budro6968

    budro6968 Veteran Member

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    Apr 2, 2016
    Jax Florida
    Try a fuel pressure gauge to see if it is putting out. I haven't checked in a long time what a carbed engine should be at. But I think you should be in the 5-7 Lbs area. Might verify that. The other thing is put the old pump on and see if it does the same thing. Some of my Buddies used to run a cool can. Basically it was an Ice bucket with a coil of fuel line in it to keep it cool. Kinda was fun to pull in to the 7-11 and pop the hood to put ice in there. People used to look at you funny.
     
  5. dph42

    dph42 New Member

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    Feb 26, 2018
    I believe you are correct on the pressure figures and I remember the cool cans. I cant use the old pump it actually cracked when my boy was trying to remove the old partial metal line. The agenda today is to at least temporarily find something to shield the fuel lines from the header heat and see how it does. If that works will go to a more permanent solution. I will still take any suggestions anyone might have. I can't believe no one has come up with an additive to raise the boiling point of these fuel blends. In my research the last week or so it appears to be a common problem. Mine appears to be boiling at about 120. Some start as low as 100
    Thanks ,
    David
     
  6. tom3

    tom3 Veteran Member

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    Aug 1, 1999
    ohio
    Any chance there's an air leak in the line back to the tank? Years ago I did put an electric pump back at the tank, switch it on for startup after a long park and when having some fun on a deserted road.
     
  7. Jeep43

    Jeep43 Veteran Member

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    Mar 30, 1999
    Connecticut
    I think your problem is the metal line before the pump is getting too hot. Its boiling and the gas that is created is stalling the pump.

    I would fashion some sort of heat shield between the headers and the fuel line.
     
  8. dph42

    dph42 New Member

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    Feb 26, 2018
    I believe you are correct I have been thinking the same thing for the past few days and here is what i have finally accomplished because of many delays and interruptions. I ran a 3/8 rubber line from the factory "splice" in the metal line about at the rear of the pass. door on the ground all the way to the fuel pump. The car has been outside running for over an hour now with the filter full most of the time.before it was only making it about 7 minutes on a warm day and 20 on a cool one. It did die once but it must have been some other gremlin cuz it restarted and there was still fuel. If any of you try this don't be like me and get ahead of yourself and cut that splice without crimping off the splice back by the tank cuz you will end up like me and be like the kid in the story with his finger stuck in the leaking dyke (dam). Everybody here is having a good laugh about me laying on the ground all by myself trying to keep all the fuel in the tank from siphoning out and not knowing what to do!
    Have any of you guys ever tried the insulating sheaths, if so how did they work out? I could wrap the headers but I would have to do both sides and I think that needs to be done before installation and not on a 15 to 20 year old set. Plus I am not really up for that.
    Thanks for all the advice and any more anyone would give, I am not done yet.
    Regards,
    David
     
  9. dave@ztech

    dave@ztech Veteran Member Lifetime Gold Member

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    Mar 27, 2016
    NY
    HAA HA , too funny on not thinking about, what will happen when you cut a fuel line, HAA HA , also, not a good idea to wrap the headers, they will not last long, see internet regarding header wraps, on mine , it was the holly fuel bowl, that would get too hot from the manifold , if I sat idling too long, had to get a carb heat shield
     
  10. dph42

    dph42 New Member

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    Feb 26, 2018
    Yeah its funny now but it wasn't when I was lying there cussing at myself for doing something that I knew better than to do! Luckily I had previously had a 67 c-10 parked in the same spot a couple of months prior that was all taken apart and on the ground was an old style dome light bulb, the ones that look like a glass type fuse only fatter. Well I shoved it in the line and it was good enough to slow it down quite a bit and I ran to the shop and grabbed a 3/8 bolt and clamp and that gave me the chance to re-group. Back to the headers I am pretty much 100% not gonna wrap them. When I get it sorted out i will post the results.I will still take suggestions! In the mean time everyone have a good laugh on me!
    Regards,
    David
     

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