Cold Start Issues

Discussion in 'Fuel and Air Systems' started by carfreak6970, Nov 13, 2018.

  1. carfreak6970

    carfreak6970 Well-Known Member

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    Hello,

    I have talked about this car here and there in my restoration thread of my 67 GTS. But this thread is regarding cold starting issues on a 70 charger:

    The problem is that if you try and start the car after it has been sitting for awhile, or when the engine is cold, it will not start. It will crank and crank with nothing happening. HOWEVER. If I spray starter fluid down both barrels, the engine wont even go through one full rotation and it will roar to life. Then you have to sit in the car and basically play with the throttle to keep it running until it starts to warm up, at that point it will idle fine on its own. Once the car is warm, restarting is not an issue.



    Some background on the car. The car has been under restoration for over 10 years, I finally got it on the road last october and really only put about 100 miles on it since then. It is a mild 440 build with a 727. Both the engine and trans were rebuilt. There were no crazy things done to the transmission, and the engine only got a slight bump in compression (due to pistons, however I dont know how much) and a mild cam. The engine was broken in. All new bearings, rings, oil pump etc. The carb is an AVS. I am not to sure what the carb was off originally, or what the carb numbers are. The initial timing is set at 12-15 deg BTC. The carb was rebuilt by my dad in the past couple years.

    I have a couple theories on why this could be happening:
    1. The choke is bad and not letting it start. It is coming off to soon hence why I have to keep playing with the throttle until the car is warmed up.
    2. The choke unloader is bad (or set wrong). and unloading the choke to soon, causing a similar issue to theory 1. - confession, not to sure if that is even possible.
    3. The carb float valve is sticking closed. Not allowing fuel to fill the bowl until the engine starts, and the added vacuum forces it open.
    4. There is a leak in the carb somewhere that allows the fuel to vaporize


    Am I far off on any of those theories? am I missing anything? Suggestions?
     
  2. JoeSBP

    JoeSBP RLTW!

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    to me it sounds like the bowls are draining into the intake(leaking power valve) and you are starting it, and keeping it running off the accelerator pump until the fuel pump fills the bowls.

    *edit Doh! just saw you have an AVS, I still say bowls are leaking down into the intake..
     
    Last edited: Nov 13, 2018
  3. tonysrt

    tonysrt FABO Gold Member FABO Gold Member

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    From all my experience with Mopar Engines it's never a problem when they are cold. When there hot that's a different story. You have a bad carb if the choke is working and it doesn't start. I've had 318's,340,383,440 and a Hemi gen2 and never a problem when cold. When cold, with air cleaner off and choke open look to see if you can pump gas into the carb. If you have a clear filter see if there is gas in it. Since it fires with a shot of fluid doesn't that tell you there may be no fuel in the bowls.
     
  4. TrailBeast

    TrailBeast Slightly Twisted Member

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    A non functional choke will act just like this and sometimes can be worked around by pumping the crap out of it 4-5 times before you try and start it.
    If it doesn't fire, pump it a few more times and try it again.
    Of course all the above is basically a work around, but it sounds to me like the choke needs fixed or adjusted correctly.

    With it cold and the air cleaner off, pump the throttle to the floor once and check the choke butterfly for being pretty much completely closed.
    If it isn't it needs adjusted.

    The fact that you have to play with the throttle to keep it running even after it does start is the dead giveaway that this is what the problem is.
     
    • Agree Agree x 1
    • tonysrt

      tonysrt FABO Gold Member FABO Gold Member

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      I thought that the people on this forum were real Motor heads. But with some of the questions I've seen, it leads me to believe that is not always the case. With the knowledge some people have on this forum it really impresses me. I've been running Mopars since 65, from my 58 Fury, 68 Roadrunner, 71 340 Duster, 77 Cordoba, 83 Town & Country & my 05 Ram Rumble Bee. All of them great cars. Today I was let down by my 05 Ram that wouldn't crank because I hadn't used it in a week and the original battery, 14 years old, said were not going anywhere. If it wasn't pouring this A.M. I would have jumped it, but instead used my other car. I did forget to mention my 10 SRT and 71 Cuda with the Gen 2 Hemi. I'm am a convicted Motor head.
       
    • JoeSBP

      JoeSBP RLTW!

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      Cool story bro. Thanks for bringing nothing to the table and taking the time and effort
       
    • tonysrt

      tonysrt FABO Gold Member FABO Gold Member

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      If you read my #3 post you'll see I tried to give him some helpful info. But I guess some guys just like to hear them self talk. So I did bring something to the table.
       
    • JoeSBP

      JoeSBP RLTW!

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      I guess, and I'm sure the older members do get tired of seeing the same questions asked time and time again. I apologize for tagging a jab.

      I'm not an AVS guru, or a carb guru at all actually, but as stated above, I'm thinking you have no fuel.
      It could be simply draining out down into the intake, or heat soak can cause it to percolate/evaporate out.
      On a cold engine, I would pull the air cleaner and look for signs of raw fuel dribbling down the carb throat. Depress the throttle fully open, and ensure the choke is resetting properly. I read on the bottom side of the AVS there are some places they are known to leak once they have been rebuilt a few times. The heat soak issue can be resolved with a spacer. I've mostly tinkered with Holley's, but I would go through and set the carb back up from A-Z. Hopefully an AVS wizard will chime in.
       
    • pishta

      pishta I know I'm right....

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      there is no where for fuel to leak out in an AVS carb, its not a TQ. If there is no fuel in it, it boiled out after the last run. use a insulator under the carb, like phenolic or plastic. When I was young, I gave up and went to a electric pump, problem solved...or worked around. the choke pull off cannot pull the choke completely off. it only allows the choke plate to move slightly under engine load.There are physical throttle stops (actually steps) involved in a choke application that need to be lowered by heat from an electric coil or exhaust heat. Push gas once to set choke on cold motor: when you do this the cold spring is under tension to pull the choke plate closed. this is tied to a throttle stop ramp that rotates under the throttle stop and props up the throttle to a fast idle position. When the warmed coil spring relaxes the choke, it rotates the curved shaped throttle stop back that progressively closes the throttle until it no longer props the throttle open. Thats why your idle gets lower and lower when it warms up. For all this to happen semi automatically, there needs to be residual fuel in the bowl. My electric would pump for 4-5 seconds every morning when I turned it on, thats how long it took to fill the empty bowls. without the fuel in the bowl, I had to crank it for maybe 10 seconds before the fuel would fill the carb, too long on a morning. Try this: put some gas in a squirt bottle and fill the bowls next cold start morning before you try and start it. Just put a few healthy squirts in the breathers outboard of the step up spring covers. Then push gas one time and crank without foot on gas.
       
    • JoeSBP

      JoeSBP RLTW!

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      no welch plugs?
       
    • carfreak6970

      carfreak6970 Well-Known Member

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      Thank you all for the responses.

      I was aware that to set the choke you have to depress the gas pedal to set it. Unfortunately I dont have much experience determining the cause when something isnt working the way it should. But you live and you learn.

      I know when I depress the gas pedal the choke blades close. The problem is I am the only one over there trying to get the thing started, so I never had the extra pair of eyes to determine if and when the choke comes off. Appears I may need to contract some help (or a starter button). However when I am playing with the throttle when it is cold it is hard to determine if the fast idle is the least bit engaged.

      The carb does have a spacer under it. The old man has been adamant about having one of those under carbs since before I came around. So we are covered there.

      So the general consensus is the choke is not operating properly. I am not to sure if this choke is the adjustable kind. I know I have seen some that were and some that weren't. But will be easy to check.

      Pishta, that is an interesting thought on fuel delivery. Now if there is a fuel delivery problem at first start up, wouldnt there also be fuel delivery issues during normal operation of the vehicle? From experience a pumps performance is what it is, it really doesnt change. This vehicle does sit about a month or two at a time before it gets started again. This issue does happen at cold start up yes. So if I run it on a Saturday, I will have the same issue on Sunday. But also have the same issue the following month. However, the 70 Polara with a similar set up (440, AVS, 727) does not have this issue. A couple cranks with that and it fires up no problem.
       
    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

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      Correct. As long as there is fuel in the bowl it should fire up in a try or two.

      Take off the aircleaner if needed. Do not try to start the car. Work the throttle lever on the side of the carb with your hand. The choke should close and fast idle screw should be sitting on the step of the fast idle cam. If these settings aren't pretty close, the rest won't work right either.

      Starting the car:
      Have you tried just giving it a few extra shots of gasoline by working the throttle? With the air cleaner lid off, you should see fuel shooting out the accelerator pumps as the throttle is opened quickly.

      OK. go and start the car. You can put the lid back on loose or leave it off. Put the wingnut where you wont loose it or drop it into the carb. Do not look down the carb while cranking.
      You can just start it from inside; or if you want to be right there under the hood, put the key in run position and use a remote starter switch or screwdriver to jumper the relay.
      As soon as the engine starts the choke will be pulled slightly further open by a vacuum operated link. After 10 -20 seconds try tapping the throttle to see if the choke's bimetal coil has moved enough to let the fast idle screw sit on the next step down.

      Since this is a modified engine, that's about right, maybe. At some point measure the timing and rpm so know what it actually is.

      1. To say the choke is bad is too general. It's initial position, and/or the fast idle position just may not be set correctly and thats why it doesn't start.
      2. Choke unloader usually is mechanical lever that forces the choke fully open when the throttle is held fully open. Its for clearing an intake which has been flooded with too much fuel. The vacuum motor that opens the choke further after start is called the choke qualifier.
      3. No. Fuel should remain in the bowls. Although given enough time the lightest, most easily ignited components will evaporate. Easy enough to check for fuel in the bowls.
      a. Remove air cleaner lid and work the throttle. If the accelerator pumps have fuel, the bowl has some fuel. The pump itself only holds enough for a few shots at most.
      b. Remove the carb top and look.
      4. Older carbs have open fuel bowl vents and open air cleaners. So yes, they lose more fuel to evaporation than later systems. Same with the intake manifold.

      Lots of additional tips about carburators and chokes, as well as explanations for the concepts can be found here:
      Master Technician Service Conference - Chrysler's Training for Mechanics
      The filmstrips and movies often supplement the pamphlets, although some cover the almost exact same thing.
      Particularly good to look at will be the 1970 Carburation Fundementals and 1969 Finer points of four barrels.
       
      Last edited: Nov 15, 2018
    • carfreak6970

      carfreak6970 Well-Known Member

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      Mattax, thank you for that. I did read those articles and they are pretty informative. Ill print them off and bring them along when I try and find out why it needs to be primed externally everytime I have to start it.
       
    • carfreak6970

      carfreak6970 Well-Known Member

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      I was able to do a little more work on this issue when I was home. So like normal I ran out of time so I wasnt able to do everything that was suggested here but I was able to find a couple things out:

      upon opening the throttle plates on the cold motor, the choke plates do close. It still cranks like no ones business with no starting. So again I had to prime it with starting fluid.

      It fired right up after that. The choke plates were still closed but if you did not feather the throttle it would die. I was about to adjust the fast idle screw when I noticed the fast idle cam was not engaged (however the choke plates were still closed). So I manually set the fast idle cam, twist the key and the car fired right up and ran on its own.

      So for what ever reason the choke plates close like they should, but the fast idle cam is not rotating into position like it should. How can that be?
       
    • AJ/FormS

      AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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      The Link-rod has to be bent just right to set it.
      If the engine springs to life with starter-fluid AND REMAINS running, then there is obviously fuel in the bowls.
      To set the choke, the blade must first close completely, and pull up the fast idle cam. Then as soon as manifold vacuum comes up,the choke pull-off can has to pull the choke off to a preset amount, which varies from one engine to the next. It could be between 2/32 and 4/32 . Then you tap the gas pedal and the cam drops to it's second highest step.There you set the idle fast speed with the screw provided, to whatever your engine likes... which varies hugely with timing.
      How long the choke stays on is governed by the preload on the bimetalic spring, and by the level of heat going into the preheat chamber under the carb. The former you have to set in accordance of the ambient temp, and the latter is controlled by the heat-riser preload spring, and the amount of heat in the exhaust and the amount of carbon in the carb heating chamber.
      All these things have to be kindof delicately balanced one against the other. Once you get it right, it's awesome. Getting it right can be a real struggle. For factory engines, the factory settings are the best place to start. And for those specs you need a FSM.
      Tips;
      >if the blade does not stay fully closed during cranking, the system will not work. With a fully closed blade, fuel will be pulled from every orifice possible by the high cranking vacuum...... but only if the throttle valves are correctly set by the fast-idle cam. The vacuum has to pass around the valves to do it's job under the choke blade. if you have set your initial timing too high, then your throttle valves will be too far closed. With a misadjusted linkrod then and not enough fast idle speed, there will be insufficient vacuum under the blade to pull enough fuel for starting, so you will have to pump the crap out of it, in accordance with the ambient temp, before starting, and continue baby-sitting afterwards.
      >If the fuel level is low, you will have trouble synchronizing the various adjustments.
      >If the bi-metal choke spring is tired it will stay on too long, and flood the engine.
      >If the choke pull-off diaphragm is ruptured it will not be able to do it's job and flooding will occur.
      >If the manifold heat-riser is not working correctly, or if you have headers,or if you have a non-factory intake on it without a heat cross-over, then the carb will not warm up properly, or quickly enough, and all kinds of problems will show up.
      >If you do have a factory iron intake on it with a cross-over...... that cross-over has to be open and clean to work properly.
      >Without the carb heat from the cross-over, icing can occur at ambient temps within a few degrees of freezing, and when the humidity is just right. This can drive you crazy cuz by the time you get the hood open, the air box off, and are staring down the venturies, the doggone ice has melted, and you never see it! Icing does not occur at or before start-up. It can occur shortly after start-up with throttle valves that are very close to closed, which can occur if your idle-timing is too high. Ya know everybody seems to want to run 20 to 25 degrees idle-timing, but here is one example where that would be too much. if the idle-timing is too high, the throttle opening will be too small to achieve your warm-up rpm. Then the engine will be slow to build heat and the choke will stay on too long. Another thing that can happen is with the nearly closed throttle, the Vcan will not be activated, so she will give you no help. The more timing you throw at the cold engine, the faster it will idle on a given throttle opening. This can be good or bad. A balance has to be found. If your spark port is active at the rpm you have chosen, then you can use the Vcan to pull in some timing. If it is not, then you gotta do it with initial plus mechanical. No big deal. Remember, this paragraph pertains to icing during the first minutes after start-up.
      >And finally, modern alcoholized fuels do not age well in vented gastanks. One week is enough to evaporate the parts of the fuel that are in there to help starting. Just one week.But worse is that the alcohol attracts water from the atmosphere.The water is heavier than the gas,does not stick to gasoline molecules,settles to the bottom, and the volatiles evaporate.So there you sit with the good gas gone and water in the wells. You can install an electric pump and do what? pump the water to the front, to add to what is sitting in the wells? meh, not my best thought. No prevention is the best policy; if you only drive the car on weekends, then don't burn alcoholized fuels. But if you have to, you can buy products to put in your fuel to bind the water to the alcohol, and then it will pass harmlessly thru your system. AFAI recall, this product does not work to bind the water to gasoline. When used as directed it will not harm your system.
      FWI
      >Icing can occur any time the ambient temp is within a couple of degrees of freezing,higher or lower,the humidity is just right, the carb is cold, and the throttle opening is very small. So this includes cruising at some hiway speeds.

      Good luck
       
      Last edited: Nov 26, 2018
      • Agree Agree x 1
      • Mattax

        Mattax Just the facts, ma'am FABO Gold Member

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        Next time, just try pumping in some extra fuel by working the throttle. The accelerator pumps will shoot fuel in every time the throttles are opened from idle or off-idle.

        Sounds like the choke qualifier isn't working, aka vacuum kick. The choke plates should open slightly as soon as the engine is running. The vacuum diaphram should be connected to a manifold vacuum source and the link to the choke as shown.
        . upload_2018-11-26_16-36-56.png

        A rod linkage determines the fast idle screw to cam relationship.
        upload_2018-11-26_16-40-35.png
        Both of these photos are of the 1968Plymouth FSM. (AVS came on 340 and 383cid engines that year) Use Drill #54
         
        Last edited: Nov 26, 2018
      • carfreak6970

        carfreak6970 Well-Known Member

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        Awesome!! thank you for that!! I have the FSM for the 70 dodge so I will have to mark this page next time I am home!
         
      • Shenango

        Shenango Well-Known Member

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        There is also a bowl vent that will come into play on the 70 Carter AVS carb. I had problems with my 70 340 and cold starts when I first got it and some linkage adjustments made a big difference.

        I'm only 60 miles or so North of you near Meadville. If you want a second set of eyes to look over your issue send me a private message. Looks like we will have temps in the 50 this weekend and a road trip sounds good to me.
        Good luck, Jerry
         
      • carfreak6970

        carfreak6970 Well-Known Member

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        I appreciate the offer Jerry. However the car is at my parents place back in Lancaster Pa