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What to do...

Discussion in 'Tech Discussion' started by thecantaloupeman, Dec 21, 2019.

  1. DoubleDingo

    DoubleDingo Summer Is Near, Hot Temps Are Already Here

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    It's called cold weather. Feather the throttle if it tries to die. Or let it warm up sufficiently before you drive it.
     
  2. SirRobyn0

    SirRobyn0 Full Access Member

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    I'm glad you dug it up because I've actually been wondering if your still having problems. I assume it idles ok? And if you hold it in the spot where it doesn't want to run will it continue to run badly or clear up after a few seconds? Well the answer I'm going to give is academic, because it's the carburetor causing this and you look to be interested in replacing rather than repairing which is fine. But my thoughts are this, accelerator pump is possible if it's not squirting or at least tricking a bit when you give it a little gas, it could be a plugged passage, but I have also seen this happen when the throttle bushings are wearing out on the throttle shaft. you'd check this by opening the throttle a bit by hand and then wiggling it up and down, a little play is normal a lot is not. So bad throttle plate bushings are essentially a vacuum leak, depending on wear and adjustment, sometimes the idle will be ok, and once the carb is fully on the cruise circuit it's ok, but in that transition and particularly cold it's run bad, I've seen them so bad they stall if you don't give it enough gas to get over that spot. I'd check the following.

    If possible it will help if the heat riser and thermac (that's the thing on the air cleaner with the flapper in the air horn), Those working will help, but if not it's not a deal breaker.

    check for possible vacuum leaks, replace any questionable vacuum lines, check the manifold and don't over look the charcoal canister, I've seen those with huge holes in them after 30+ years of service. Vacuum issues should also affect idle, but it would be good to eliminate this possiblity before shelling out $$ for a new carb.

    If you decide to switch over to the edlebrock, I would not discourage you from doing that but do be aware that you'll be setting up the carb from scratch, so this will mean setting the choke for the first time, duration and idle speed, and then fine tuning. Setting up the idle mixture and speed as well. If switching to an edelbrock you'll need to run a rubber line or bend a new metal line from the fuel pump to the carburetor, and you'll need a new inline fuel filter before the carb and the edelbrocks do not have a filter in the inlets like the Q-jets do. If you have a 700R4 transmission you'll need a geometry correction kit because the cable from the carb to the transmission has have a certain amount of movement or it can damage the transmission. If you're keeping the original intake manifold you'll need an adapter plate for the carb, and getting a heat insulating gasket to prevent peculation is good idea. you may need to install a fuel pressure regulator as well. Edelbrocks don't like to much fuel pressure and sometimes the fuel pumps produce to much for it. I know that sounds like a lot, and in a way it is but none of it is particularly hard. The biggest thing to me is getting it dialed in especially the choke and fast idle. I will admit I'm down right anal about how my truck runs, so for me that meant starting it, making changes and then waiting for the next cold start to see if I needed to make more. If you take your time the edelbrocks can be great carbs and you may see an increase in gas mileage from it.

    That is one approach, and for some folks that's good enough, but like I said I am anal about how my truck runs, so you can bet my truck will start with one pump of gas well below freezing and after less than 30 seconds of idling you can kick it down and drive off if you wanted to.
     
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  3. HotRodPC

    HotRodPC Administrator Staff Member

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    I agree. I was going to ask how old he is, and I see he's 19. Exactly, it's called Cold Carbed Engine. You want to know one of the advantages to fuel injection and computers? There's one of the biggest ones right there. Your issue sounds totally normal to me. You can fix this by havin a properly working choke to let it run richer until it's warmed up, then you can take the choke off and it'll run just fine.

    If you've ever read an owners manual for a vehicle in the 60's maybe even early 70's, you'll see there is starting procedure and allowing it to warm up before you take off. Computers and FI took care of all that. Just start and go. The computer is doing the tuning and this is also why the Temp sensor and having a properly working thermostat are important to a computer controlled vehicle.
     
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  4. DoubleDingo

    DoubleDingo Summer Is Near, Hot Temps Are Already Here

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    Mine fires with a tap of the key when cold, choke operates like it's supposed to, but on cold mornings like now it'll do exactly what he is reporting his is doing. Feather the throttle when it sputters and voila it is taking off like normal. Once it's warmed up no feathering is needed.
     
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  5. thecantaloupeman

    thecantaloupeman Full Access Member

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    Thanks for this response. I didn’t know replacing the carb with an Edelbrock need this many things. I was planning on replacing the intake too, but I didn’t think there was much more to it. I am totally not opposed to fixing it, but it would be nice to just buy a new one and be done with it instead of fiddling around with one that may not have been properly rebuilt. That way I can upgrade my intake too.

    I don’t think this is a regular cold start issue because it wasn’t all that cold yesterday. It still felt like spring, there was a tiny wind chill but not cold at all. I know a carbureted vehicle isn’t supposed to start right away in the cold and that there is a different starting procedure but this is much different.

    When I held the pedal in that one spot it didn’t really clear up until I gave it more gas.

    Normally when I first start it I need to pump the throttle a few times to it doesn’t stall out from the low rpms. This time however, pumping the throttle actually made it sputter more. Once it passes that one spot in the throttle it gets sort of stuck in those lower rpms trying to overcome the loss in rpms and sometimes it takes a while to match where the pedal is and there is a delay.

    Normally it just increases the rpms with the pedal travel as usual. Normally if I let go of the throttle the engine eventually dies and I have to start again. Which is totally normal. But I feel like this isn’t a regular problem. Something isn’t functioning properly. It shouldn’t be idling fine, and then lose rpms when I ever so slightly press the pedal. It only does this right at the beginning of the pedal travel.


    Sent from my iPhone using Tapatalk
     
  6. Snoots

    Snoots Supporting Member Supporting Member

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    ? Sticky advance weights ?
     
  7. DoubleDingo

    DoubleDingo Summer Is Near, Hot Temps Are Already Here

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    I'm still saying it's a cold engine thing. Notice I said cold engine? Outside temp, whether it is blazing hot or freezing cold only affects how quickly the engine gets up to operating temperature, until it does get up to operating temperature you still have to drive it a certain way. Mine has vortec heads and intake which don't have the heat crossover under the carb, but I tell you what, once it sputters and I feather the throttle it will take off like it's fully warmed up. The next stop I'll have to feather it again to take off. I'm a quadrajet guy, wouldn't buy an edelbrock or a holley yet there are those that swear by them. A quadrajet is the most reliable carb you can have, you'd been money well spent going with a q-jet. But I digress.
     
  8. Backfoot100

    Backfoot100 Full Access Member

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    Pumping the throttle once or twice before you ever start it should be setting the fast idle cam. If the cam isn't setting right, it needs adjustment or the fast idle set screw needs to be turned up a little bit to increase your fast idle RPM.
    If everything is working and set properly, after you start it, you just touch the gas pedal a little bit which releases the fast idle cam and knocks it back down to regular idle speed.

    I pump mine twice before starting cold and can almost immediately put it in gear and pull it out of the garage without touching the gas. I only pull it out right away so the exhaust fumes aren't so bad in the garage.
    Then I let it sit in fast idle for a minute or two, touch the gas to kick it back into normal idle speed and I can drive off however I want to. Never a hiccup at all. Thats how its supposed to work.

    Once you start it, if you have to feather or pump the gas to keep it running you're disengaging the fast idle cam before it can do what its supposed to do. Or the fast idle cam and/or the fast idle set screw isn't set right to start with.
     
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  9. SirRobyn0

    SirRobyn0 Full Access Member

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    Thank you for that, sometimes I feel like lots of other folks think it is normal for a carbed vehicle to run like crap when it's cold and it is most definitely not normal.

    Basically it comes down to this, if someone is happy having to feather the gas to keep their truck running when it's cold then that's fine, but don't confuse that with normal. It's not. thecantaloupeman clearly isn't happy with the way his truck is running and has some great info from a few of us to help him find the issue.

    Personally I'd rather not see this thread go down the which carburetor is best rabbit hole, he asked about edelbrocks that's why I went there. I will say I agree that the Q-jet is the better carb, but I'm not about to suggest he do a home rebuild on his because Q-jets can be a bit tricky for someone that has newer done one before where as the edelbrocks are relatively easy to adjust. Another option might be to purchase a rebuilt Q-jet that he could bolt on, if you go that route you'll need to be careful where you get the rebuilt from as there as that are not so great.
     
  10. DoubleDingo

    DoubleDingo Summer Is Near, Hot Temps Are Already Here

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    LOL...you funny...if you rode in my truck you would see I clearly have it dialed in and am not feathering the throttle all the time...lol...when cold yes and only from a stop because of no heat crossover on the vortec setup. I'm out. The kid doesn't listen to reason very well anyhow.
     
  11. SirRobyn0

    SirRobyn0 Full Access Member

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    Maybe your right, the thing is none of us can drive his truck and say for sure.
     

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