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Technical Possible vapor lock?

Discussion in 'The Hokey Ass Message Board' started by Mack.c, Oct 18, 2017.

  1. Mack.c
    Joined: Oct 17, 2017
    Posts: 8

    Mack.c

    1E8B7BEB-8E36-4DC8-8F5B-8B0224B62662.jpeg I have a 46 merc with sbF 302. When cold it starts and runs fine with fuel filter on carb side full. When the motor heats up the filter starts emptying out and motor dies. I have a new electronic fuel pump(Holley blue), rebuilt Holley carb, new coil, wires, and plugs. Brand new tank as well. Any help would be appreciated. Also has anyone ever ran a return line for the fuel system to circulate?
     
  2. sloppy jalopies
    Joined: Jun 29, 2015
    Posts: 5,256

    sloppy jalopies
    Member

    don't know about the lock... but to recirculate the fuel stirs the gas in the tank... helps keep today's gas from gelling... buddy / mechanic will not run a carb on any of the rods he builds...
    runs injection so it stirs the tank...
     
    Mack.c likes this.
  3. Mack.c
    Joined: Oct 17, 2017
    Posts: 8

    Mack.c

    I might look into that. I’ve been having this problem for a while now.
     
  4. LBCD
    Joined: Oct 28, 2009
    Posts: 1,059

    LBCD
    Member

    Fuel line getting too hot more than likely, need to shield the supply line and a phenolic carb spacer. Nice 46 and 41 in the pic!


    Sent from my iPhone using H.A.M.B.
     

  5. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 9,214

    mgtstumpy
    Member

    What about the gas tank breather (vent) line, it could be clogged or collapsed causing a vapour lock? It needs to be open to allow in air to displace the gas being used by the engine. Just a thought.
     
  6. Is the fuel also being routed thru a mechanical fuel pump? Where is the electric fuel pump located, and is it mounted above the fuel level in the tank?
     
  7. Mack.c
    Joined: Oct 17, 2017
    Posts: 8

    Mack.c

    Never even thought about the vent line. Good call. I will Check that out tonight!
     
  8. Mack.c
    Joined: Oct 17, 2017
    Posts: 8

    Mack.c

    No it’s just the electric. It’s located slightly below the tank
     
  9. Mack.c
    Joined: Oct 17, 2017
    Posts: 8

    Mack.c

    I do need to insulate the line for sure.
     
  10. Mack.c
    Joined: Oct 17, 2017
    Posts: 8

    Mack.c

    They just opened a summit by my house in Arlington tx. Looks like I’m stopping by there to get parts
     
  11. Mack.c
    Joined: Oct 17, 2017
    Posts: 8

    Mack.c

    Thanks man, great looking headaches they are lol
     
  12. Well that eliminates a couple of potential issues. I'd say the next step would be to run the engine till it warms up and stalls. Then disconnect the fuel line at the carb, route the line into another container and turn the pump on and see what kind of output it has. And as already mentioned, make sure the tank is properly vented. Or loosen the filler cap and see if that allows more fuel flow.

    Is there a filter anywhere inline between the pump and the carb?
     
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  13. It should be fairly easy to add a return line to the tank.. you can drill the filler neck and use JB Weld on the fitting, and add or replace the filter with a "return line filter" that has a restricted return fitting on it. This is what I did ... not knowing that my problem all along was a defective ignition module. (ok, dumb - shoot me..ahahah)....
    https://49fordcoupe.smugmug.com/Fighting-Vapor-Lock/
     
    Mack.c likes this.
  14. Mr48chev
    Joined: Dec 28, 2007
    Posts: 33,861

    Mr48chev
    ALLIANCE MEMBER

    Especially if the gas cap is new and the car quits right at about the same amount of running time every time I'd be looking into making sure that the cap is actually vented.
    I see that you answered his post further down.
    Two simple ways to test it. Run it until it quits again and remove the cap and see if air rushes into the tank. It may seem like it is coming out but it would have created a vacuum in the tank. If the gas level is low you might hear the side of the tank pop back out. The other way would be to leave the cap loose or off and see what happens.
    Vapor lock issues that I have had always have happened while running in hot weather and under a load. But that was a cooler full of Ice water dumped on the intake and fuel pump a 44 ounce cup at a time pulling a grade in Utah in 1977.
     
  15. Mack.c
    Joined: Oct 17, 2017
    Posts: 8

    Mack.c

    There is a filter between the tank and fuel pump, and one between the pressure regulator and the carb
     

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