Percolation? Heat soak? Don't drive during summer??

Fuel and Air Systems

  1. DentalDart

    DentalDart Well-Known Member

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    My car has done that since I got it last year. Crazy to think I've only had the car a little over a year.
     
  2. RustyRatRod

    RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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    I agree. I cannot believe he hasn't done something about that yet. It's been like this ever since he got it running. I would put another ECU and coil on it. Period. Somethin's up with that crap.
     
  3. DentalDart

    DentalDart Well-Known Member

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    It was like that before I took it apart and it never caused a problem... that I know of.
     
  4. RustyRatRod

    RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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    Well you need to fix that. That could be what's wrong with it. If that coil is putting out all the time, it's probably overheating. That could be the coil itself, or the ECU. I caint believe you ain't addressed that yet. lol
     
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    • Phreakish

      Phreakish Well-Known Member

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      Strange. I thought it was a new symptom after it was back in..
      I keep misremembering things from your other threads!

      It's still not normal and may be causing other parts to go bad or it's caused by something else already being bad that gets worse with heat..

      I'd see if bypassing (temporarily) the ballast changes it, or confirm the tach is the cause. A good tach shouldn't cause that..
       
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      • AJ/FormS

        AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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        That sparking business I have never seen before!

        I skimmed the thread from the beginning and did not see anyone mention that both the carb and the tank have to be vented.
        Neither the pump nor the carb actually suck fuel. It is the 14.7 psi of atmospheric pressure that enters the tank thru the vent, then pushes the fuel to the front, in response to the pump creating a tiny low pressure area inside of it. Once there, the pump pushes it up to the float bowls. From there, it is the low-pressure inside the chambers on the intake stroke, that prompts the atmosphere to push fuel up and over the idle/main wells.
        If your float level is too high, it becomes too easy for the atmosphere to push the fuel over. If too low, then too difficult.
        Gasoline is made up of many different molecules, the lightest of which boils at about 95*F. If it is boiling in the bowls, then it is also boiling in the wells. With the engine running, this is no big deal because the bowls and the wells are vented, so it just escapes back into the atmosphere. And your engine does not need or want that crap that is boiling anyway; it is only in there to help your car start/run when the engine is cold. As the switch-over to EFI is happening, eventually I suspect, the formulators will phase that constituent out completely.

        Up here in Manitoba, we don't have your high-heat problems. But we do have a significant base elevation that ranges from about 1100 ft just West of me, down to 800 ft about 30/40 miles East of me. I am at 930 ft. Elevation changes the boiling points of all the molecules. And we have daily temperature swings of 40 to 60 degrees F .. So I need that lightweight skunk-pizz.
        This is another reason I have a mechanical fan...... it turns continuously...... continuously blowing on my aluminum heads, my aluminum intake, and my aluminum bodied carb; continuously cooling those, and then continuously pushing the hot air down and out to underneath the car.. Yaknow; I don't care how much power my T-clutched,7-blade, large-diameter, all-steel fan, sucks; I will never ever install an electric system.
        Now, consider this; where is your carburetor vent?
        On a Holley it is in the airhorn with a standpipe, inside the air filter house, semi-protected from the underhood air dynamics.
        But on a Carter-type carb,the last time I looked it was on the top of the bowl with a mechanical lifter arm, synchronized to throttle movement, OR it was terminated in the charcoal canister. What happens when my factory 7-blade starts pushing hot air across the vent hole? I mean IDK, and I don't want to know, which is just one of the reasons I don't run that type of carb. The bowl HAS to have access to a constant atmospheric pressure.

        Overnight, those lightweight VOCs evaporate, leaving you with the heavy stuff to try an ignite in the morning. The boiling points of those remaining vary all over the place, with the heaviest not boiling until 450*F, IIRC. So then lighting that syrup with a cold plenum, cold runners, and cold chambers gets a lil more difficult. And your Idle-timing is way retarded, so even if whatever gets lit, a lot of it is gonna go straight thru the system, and out the tailpipes,.... until the metals warm up some. And because of the retarded timing, the engine has very little idle-power either, until it warms up.
        But, you say, your idle-timing is NOT retarded.
        Oh yeah?
        Next time your engine is cold, in the morning; immediately after it fires up, just start cranking in some timing, until the engine rpm stops increasing. Now read the timing. What you see there is the correct amount of idle-timing for whatever the rpm rose up to. I'll guess you will see hi 30s to mid 40s. So even if your idle-timing is set to 18*, it is less than half of what the cold engine wants. And so, that is where the lightweight VOCs come in handy.
        Put a scanner on your EFI car, and see how it is programmed....
        In any case, I really just wanted make sure the vent was not overlooked. Good luck!

        As for me; I keep a 500cc bottle of fresh fuel under the hood, into which I have mixed stabilizer and 5% two-cycle oil for ring sealing and lube. I have installed the air filter house on top of the hood and sealed the underside of the hood to the top of the carb. So when I open the hood, shazzam there is my airhorn staring back at me. I squirt some gas in there, close the hood, jump in and twist the key; and instantly it fires up. Immediately, I dial in some advance with my dial-back timing box, back out of my carport and idle out thru the neighborhood. About three/four miles later,on the hiway now,the car surges forward about 3 to 5 miles an hour, indicating to me, that the engine is ready. I retard the timing back to normal, and it's go time!
         
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        • DentalDart

          DentalDart Well-Known Member

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          You co fused me with some of this... my car doesn't have EFI, its to expensive. Just a mech fuel pump (old one) and new avs2 carb. My fuel tank is vented. My timing doesn't advance past 36* as we installed a timing advance kit, unless even with the kit its able to advance farther than that when warming up? I have a new mechanical fan with a clutch on it.

          Yes the sparking at the coil is weird and no one has ever seen it before? Lol.
           
        • DentalDart

          DentalDart Well-Known Member

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          It doesn't do that constantly, only when I turn the key to the on position before I start cranking it over. Once I start cranking the engine over the coil is normal and will only do that again if i turn the key all the way off and then back to the start position before cranking it again. Its weird, I always thought I had an electric pump until Tony found the coil doing that...
           
        • RustyRatRod

          RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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          He's an expert in that field.

          He's not paying attention.
          Get that off there. Do you need some parts? I might have a spare 12V coil I can send. I may also possibly have an ignition box. I'm not sure. I'll look tomorrow for either or both.
           
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          • RustyRatRod

            RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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            Then by all means, ignore all of us and leave it on there. What WERE we thinking trying to help?
             
          • AJ/FormS

            AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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            this is a test to verify what I earlier said, about all non-EFI cars being handicapped with retarded Idle-Timing, of necessity.



            I mean your other car, the one you normally drive,lol. Or your wife's car, or Mum's, any EFI car,lol. You will see how much cold timing the factory dials into them, so you can have a super nice drive-away.
             
            Last edited: Sep 21, 2020
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            • Phreakish

              Phreakish Well-Known Member

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              I found one other internet post of a guy with constant on coils, but it was a coil pack fired corvette with efi.. So not much help with solutions.

              The coil stores energy when current passes through the primary winding. When the primary is disconnected, the secondary picks up a voltage spike which gets turned into your spark. A constantly firing coil could be caused by any number of intermittent connections. The ecm could be failing, there could be a loose connection at your pickup or at the ecm. A bad plug to your pickup. A faulty ground somewhere associated with the distributor. Or even something in the ignition switch? It's hard to say without some testing. Typically a faulty connection won't stay consistently dodgy like that since the arcing going on will typically erode something and cause the connection to fail or at least melt.
              Since it keeps doing it, I suspect the ecm is the cause but have no way to say for certain. It's just the one place I could see a transistor or something being right on the edge for a prolonged period, and when it gets warm enough it may just shut down or remain in the "switched off" state with respect to the coil ground.
              But you say the spark is still present and constant on like that, even after the engine quits. It's possible the switching becomes so fast that the coil can't absorb enough energy and fails to jump the spark gap once hot..

              This is one of those cases where it's not simple or obvious.. So it may be that parts swapping is the only "easy" way.

              I'd wager that once this symptom is fixed, it stays running more than 20 mins.
               
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              • AJ/FormS

                AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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                Rusty,what makes you think he needs a coil? Ima thinking you need more sleep.
                I mean OP could practically weld with the one he's got. I have never seen that behavior but coil would not be on my list of things to change, nor would an amp. I'd be looking into what could be telling the amp to fire like that, and of course I would be disconnecting the tach pronto, as others have suggested.

                Since the engine starts and runs normally, Ima thinking the amp is being triggered by something else.
                 
              • 69_340_GTS

                69_340_GTS Well-Known Member

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                I had a heat-soak problem on my '69 GTS that had a Mopar electronic ignition installed by the previous owner. After fooling around with carb heat shields, fuel pumps, and all the other fuel-related stuff, I decided it had to be ignition-related. When electronic stuff gets too hot, it often malfunctions. The good stuff, made in USA in the '70s-'80s, was not very prone to having these heat problems. The new-ish OEM (or other) replacement electronic parts, from China, India, Pakistan, etc... such as ignition boxes, coils, ballast resistors, are pure junk for the most part. And I'll bet that's what is on DD's car. I had numerous resistors burn out prematurely. I had a fairly new Mopar ignition box completely melt, and all that plastic goop ran out of it. Of course the car died. The answer? My solution was to go with all MSD. When you install an MSD 6AL ignition box, the ballast resistor is eliminated. That alone is a great 1st step towards reliability! You will also have to buy the recommended MSD coil. And if you really want to make it bullet-proof, get a new MSD distributor too. Of course, due to the male distributor cap on it, you'll need a beautiful new set of wires too. But that's O.K., because I have had no problems with heat ever since I replaced all those crappy ignition parts.
                 
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                • 318willrun

                  318willrun Utube channel 318willrun

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                  Sorry, just skimmed through this thread. When it don't start, did you pull the coil wire from the distributor and verify it has spark?
                   
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                  • Phreakish

                    Phreakish Well-Known Member

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                    See post 74.
                     
                  • 318willrun

                    318willrun Utube channel 318willrun

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                    That's with it off, correct? How about when he's cranking it over....
                     
                  • j par

                    j par Well-hung Member

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                    And your question verified you did not read the thread...
                     
                  • j par

                    j par Well-hung Member

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                    While I like msd and have it myself I always have a hard time recommending a $450+ investment like that for a fix...
                     
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                    • 318willrun

                      318willrun Utube channel 318willrun

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                      Another question, when you try to start it and it won't start, does it give a brief cough when you let off on the key from trying to start it? Reason I'm asking is I've seen pickups in the distributor act like that when hot. Just throwing it out there, hard to diagnose over the internet.
                      *and yes, I seen where the distributor was rebuilt and had a new pickup. Sometimes things don't work properly right from the box.
                       
                      Last edited: Sep 21, 2020
                    • DentalDart

                      DentalDart Well-Known Member

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                      That video posted was with my Old coil... my New coil does the same thing though...
                       
                    • DentalDart

                      DentalDart Well-Known Member

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                      When cranki g the car over the coil acts normal. It only does that when i first turn the key to the on position before starting to crank it over. Once I start to crank it over it goes normal.
                       
                    • 318willrun

                      318willrun Utube channel 318willrun

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                      Ok, so I'm reading that you had somebody crank it over while you held the coil wire and it fired normal while it was hot and wouldn't start. Then did you check the spark coming out of the distributor the same by pulling a plug wire and putting a spark plug in it, while it's hot and won't start?
                       
                    • yellow rose

                      yellow rose Overnight Sensation

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                      That’s an issue with that type of carb (just like a TQ or a Q-jet) because the fuel bowls sit right over the hot intake manifold.

                      It’s great that you blocked off the crossover. An electric pump is a bandaid.

                      When the engine is turned off, the temp climbs even higher and the carb gets hotter and the fuel boils off. An electric pump doesn’t fix that.

                      Ive had them do the same thing sitting at a long stop light. The engine quits and then acts like it’s flooded (because it IS flooded from the fuel percolating out of the float bowls), but because there is no fuel in the carb, you have to crank the hell out of it to get the bowls filled AND get rid of all the excess fuel.

                      I have a 73 Duster sitting in my driveway right now that had the exact same issue. I live in a hot climate, so it was a PITA. The Cool Carb heat shield fix 98% of it. You can’t fix all of it because of the design of the carb.

                      The alcohol in the fuel doesn’t help, but that’s not all the problem. The number one issue is the design of the carb.
                       
                    • yellow rose

                      yellow rose Overnight Sensation

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                      A2EF6F87-C179-482C-9223-31CC97D7CA2B.jpeg 639CCCAF-34F0-4A36-A8DC-857E33186D03.jpeg 99B9168C-8E26-47C7-BAE2-696B8B3EBA3C.jpeg 50620E9F-A068-40A0-BBF2-C2F61EE3B237.jpeg

                      Here are the pictures of the heat shield I use. I’ve used several of them. I had forgotten that I took pictures of it.

                      It won’t fix all of it, because when the ambient temp is high enough, it will still boil some of the fuel off when you shut it down. But it will stop most of it.

                      No other spacers or heat shields ever did anything but this one. The first time I used it was on a 67 Firebird with a cast iron intake and Q-jet. He spent a bunch of money and the only thing that helped was this.
                       
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