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  • Another MC2100 Question

    I hope someone can tell me whats going on here.

    I had a Carter non BBD on my 86 CJ. I was having really performance problems. I swapped it out for a MC2100, and I have seem to traded one set of problems for another.

    Without going into detail about the previous issues, I now have some rather peculiar issues. I'll try to list them below.

    1. Hard starting. I'll roll the engine over several times. Nothing. Many times when I release the ignition key switch, I get a blow back up through the carburetor. Sounds kinda like a phewwwwww. It's like it's trying to start but will not. After several attempts, it will start.

    2. The electric choke works, closes off when cold, opens up when warm. During the process of cranking, it will open which I think is making it harder to start.

    3. Screw settings. The idle mixture screws are set to 1 3/4 out from bottoming and the idle screw is set to 1 1/2 turns.

    4. I cant keep it idling at a steady rpm, recommended curb idle is 680 rpm. It wants to run around 800 to 850. The idle screw has no effect at this rpm level. I can increase it and increase the idle speed, but lower is end is not there.

    5. I've tried to set the carb using the lean drop method, but when I back the idle mixture screw back out, the rpm speed just keeps increasing to a couple thousand rpm. I run it back in and the engine speed does not drop off like I have read that it should. The engine just dies. Which is an indication of good vacuum.

    6. I have no vacuum leaks. I've measured it, and it runs around 20 inches.

    7. Timing is set to 9 degrees BTC.

    8. I have done the Nutter bypass.

    9. I still have the PCV system connected and the EGR circuit. EGR is closing, I can reach my fingers in and press on the diaphragm opening the EGR and the engine stalls.

    10. When I get it out on the road and run it, I get a stutter when I load it, like when I'm coming up the drive way in second gear and give it gas. It stutters and spits and I have to shift down into first.

    Thanks

  • #2
    Originally posted by birddawg View Post
    I hope someone can tell me whats going on here.

    I had a Carter non BBD on my 86 CJ. I was having really performance problems. I swapped it out for a MC2100, and I have seem to traded one set of problems for another.

    Without going into detail about the previous issues, I now have some rather peculiar issues. I'll try to list them below.

    1. Hard starting. I'll roll the engine over several times. Nothing. Many times when I release the ignition key switch, I get a blow back up through the carburetor. Sounds kinda like a phewwwwww. It's like it's trying to start but will not. After several attempts, it will start. Ford type ignition? maybe the crank circuit kaput or accelerate pump not giving initial shot

    2. The electric choke works, closes off when cold, opens up when warm. During the process of cranking, it will open which I think is making it harder to start. That is wrong. Give the choke some extra tension so it stays closed. Should actually snap closed when operated. There is a vacuum circuit that will open it about a 1/4" once running

    3. Screw settings. The idle mixture screws are set to 1 3/4 out from bottoming and the idle screw is set to 1 1/2 turns. Good basic start

    4. I cant keep it idling at a steady rpm, recommended curb idle is 680 rpm. It wants to run around 800 to 850. The idle screw has no effect at this rpm level. I can increase it and increase the idle speed, but lower is end is not there. At 850 it is running not idling, Possible vacuum leak and acclerater pump issue

    5. I've tried to set the carb using the lean drop method, but when I back the idle mixture screw back out, the rpm speed just keeps increasing to a couple thousand rpm. I run it back in and the engine speed does not drop off like I have read that it should. The engine just dies. Which is an indication of good vacuum. idle mixture screw has no effect when running, ie throttle plates open. Makes me wonder if the bowl is set high. Don't understand how adjusting the air mixture can achieve an idle of 2k

    6. I have no vacuum leaks. I've measured it, and it runs around 20 inches.Did you measure it at 850 rpm or the crappy idle speed? Would expect excellent vacuum when running at 850rpm

    7. Timing is set to 9 degrees BTC. set ofcourse with vacuum line disconnected from dizzy

    8. I have done the Nutter bypass.?

    9. I still have the PCV system connected and the EGR circuit. EGR is closing, I can reach my fingers in and press on the diaphragm opening the EGR and the engine stalls. good

    10. When I get it out on the road and run it, I get a stutter when I load it, like when I'm coming up the drive way in second gear and give it gas. It stutters and spits and I have to shift down into first.Accelerator pump

    Thanks
    Again these are just my opinions based on the little knowledge of carburetors I have but I manage to get by ok todate

    Comment


    • #3
      Vacuum leak would be my guess. Did you use and adapter plate of some type when you mounted the 2100? (not sure if you need one for the 2100 or not) I switched carbs once and had almost the same issues. If I tried to let it idle, it would die. If I gave it just a little gas it would run smooth. I couldn't start it right away... had to pump the gas and to give it gas to fire. Found that I had the carb gasket on backwards which created a very small opening to the rear of the carb.

      Other than that, I have no clue and wish you luck

      Comment


      • #4
        One issue I had with my conversion was the linkage hit slightly on the manifold. I had to grind it down so it would clear. Got good idle after that.

        However, I agree with the acc pump as stated already. If that and/or the float is off, your MC2100 will do all kinds of nasty things.

        Also I would surely check the ignition as stated too. If the old carb was not the sole cause of all the issues, then those problems are still there. A dying spark box can really ruin yer day. I swapped mine to an E-coil (Ford TFI) when I swapped my carb. I wound up at 8 BTDC, so that sounds good there...as long as the vacuum was disconnected as stated too...that will really throw off the reading. Also tho, hard top get an accurate timing set if it's not idling right. May just try the backwoods timing of loosen the bolt, get it to start and turn the dizzy until it runs best. Then tinker with the idle and then set the timing the right way once it runs better. I like white crayon to mark the dizzy and the timing marks to make it all easier to see and re-align should it slip or just not work.

        Comment

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