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Thread: Back to my fuel vapor in the lines.

  1. #41
    Registered Member WagonCrazy's Avatar
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    What is the heat source that's causing the boiling? Do you have a fuel line up against an exhaust component?
    1957 Nomad- LS1/T56 on C4 chassis
    1959 Fleetside Apache 1/2 ton, shortbed, big window, 327ci.

  2. #42
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    Tony there's no magic. Something is wrong. You could try some race gas or av gas, but that's not what you want to run, so why even do it?

  3. #43
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    Quote Originally Posted by WagonCrazy View Post
    What is the heat source that's causing the boiling? Do you have a fuel line up against an exhaust component?
    Right now I'm guessing the fuel pump is getting hot from both the heat from the radiator and the heat from the block, although I do already use a 1/8" insulating spacer between the pump and the block. And yes I didn't think of it recently but evidently I'm not the only one with that problem or they wouldn't even make the insulating spacers for it. https://www.cantonracingproducts.com...&category=8510
    Tony

    1955 Bel Air Sport Coupe

  4. #44
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    Quote Originally Posted by Rick_L View Post
    Tony there's no magic. Something is wrong. You could try some race gas or av gas, but that's not what you want to run, so why even do it?
    Rick, please excuse my sarcastic outburst, but I've been dealing with this problem for about 5 years now and I keep telling people that it is heat related and they keep ignoring that fact.
    I'm thinking of an electric fuel pump near the tank. I have run various kinds of insulation on the fuel line in the engine bay and they didn't help.
    Tony

    1955 Bel Air Sport Coupe

  5. #45
    Registered Member WagonCrazy's Avatar
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    Tony,
    Don't mean to be belittling or beligerant here. Just helping you sleuth this problem with some objective thinking...

    Heat is common with all engines. The original SBC and BBC never had a heat insulator necessary between the mechanical fuel pump and the block. So if your engine is creating that much heat, then you have to ask yourself why so much heat beyond a standard engine?. Run it and take a cheap Harbor freight laser thermometer and check the block temps around the top of the pistons, bottom of block, etc. Is it more than boiling point (say 250 degrees) near that fuel pump? Is the pump the same temp as the block (when running of course)? I like Laszlo's suggestion of starting simple and diagnosing each component from the carb back.

    So, couple of thoughts:
    Your video with the engine running and viewing the fuel filter (to me) seems to show not enough fuel flowing thru that filter. I suspect your pump. So pull the feed line to the pump, install a 2 foot length of rubber hose and feed the pump with a small tank of fuel with that line drawing from it. Then shoot a video of the fuel filter with the engine running and compare the flows. If it flows at a higher rate, then you know the fuel pump is being starved somewhere BEFORE the pump. (The lines themself or the tank pickup). If the flow rate is the same, then you know the pump is consistent, but maybe not putting out the 5 to 6 pounds of pressure as it should. Put a gauge on the backside of the pump and run it again and check the pump output pressure.

    If your fuel system is not passing enough fuel during driving, then it will eventually starve the carburetor. The bowls will run dry and the engine will stall while driving. Can you confirm that it's running the carb dry during driving? Or is this a "no fuel at warmed up startup" problem?
    1957 Nomad- LS1/T56 on C4 chassis
    1959 Fleetside Apache 1/2 ton, shortbed, big window, 327ci.

  6. #46
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    I think I've checked the temp of the block but it's been a while. I know I've tried to check the temp of the fuel pump but those infrared thermometers don't work well on reflective surfaces and it's chrome. In that video there is a tiny bit where you can see my hand down near the pump. I thought the pump felt hotter when it was boiling than when it wasn't but that isn't a great test.

    To shoot that video I first ran the car on the highway to get it hot, then let it sit in drive with the parking brake on and the hood closed for a while. I don't think it's that bad when driving, but yes it does run out of fuel going WOT from 1st and if it's hot it will die in 2nd. The accelerator pump in a Q-jet has it's own reservoir that doesn't go dry with the rest of the bowl, so pumping the pedal will give it short bursts of power. So yes I know the bowl is going dry.

    Next time it's warm enough here to test it and it's bubbling in the filter, I plan on hitting the fuel pump with a garden hose to cool it down and see what happens. That is a lot easier than changing fuel lines on a "hot off the highway" engine, but I will do it if the cold water doesn't stop the bubbling.

    Just to catch you up in case you missed it, I have changed pumps and ran an all new 3/8" line with no improvement. A while back, years ago, I cut the lower part of the baffle next to the radiator and made a half ass baffle to direct cool air to the pump, and that helped a lot, but only on the highway. That isn't in place now, I forget why/when I took that out. Thinking of that now I suppose I could install another tube similar to the cold air intake but one that blows directly on the pump. Yes it would only help while moving, but it would be much more efficient than the baffle I had in there before. I have some real ugly galvanized flexible tractor trailer exhaust pipe I could try it with and if it works get some shiny stuff like the air intake.
    Tony

    1955 Bel Air Sport Coupe

  7. #47
    Registered Member BamaNomad's Avatar
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    Could this another case where the 'chrome' is a part of the problem???

  8. #48
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    Quote Originally Posted by BamaNomad View Post
    Could this another case where the 'chrome' is a part of the problem???
    I was wondering the same. what kind of pump is it.

  9. #49
    Registered Member Troy's Avatar
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    My dad always says...If it don't go chrome it!!! This seems to be if it's chrome it don't go!!!

  10. #50
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    What? What would the chrome do? Oh, maybe the seal would leak sucking in air? I have to run out for some things and I'm taking the 55. See how well it runs today that it's cold out.
    It's a Holley pump, and the same one before it gave the same problem.
    Tony

    1955 Bel Air Sport Coupe

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