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Thread: '84 B2000 carb problems

  1. #1
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    '84 B2000 carb problems

    Hello forum!

    I have a 1984 Mazda B2000 I've been driving for about a year now. Now that winter is upon us, I thought I'd rebuild the carb and adjust the choke to make it easier to start in the cold.

    I have the carb back together, and I also took off all the EGR and smog stuff (I'm exempt from emissions and it wasn't working anyway). I made a blockoff plate for the intake manifold and I blocked the exhaust fitting off by removing the EGR pipe and putting a nickle in the fitting. :mrgreen:

    The problem I'm having is that I can't seem to get the carb to tune right. If I were to describe all the symptoms it would probably sound like a vacuum leak...

    1.) Won't idle below 1000 rpm
    2.) Idles and revs smoothly in neutral
    3.) Loses all power above 2000 RPM in gear
    4.) Won't run unless the mixture is rich
    5.) Won't run unless the choke is almost completely closed, even at operating temp.

    The part I don't get is that my vacuum gauge shows 20lbs of vac. I also tested it for vac. leak by spraying starting fluid around the manifold and vac. connections, it didn't seem to effect it any, so I don't think its a vac. leak.

    And I thought it might be that the spark isn't advancing, but the timing seems right and it is advancing. I recently replaced the cap, rotors, wires, and plugs, and I gapped the plugs to spec.

    I have no idea what my problem might be, I am going to check for fouled plugs tonight, other than that I'm at a loss... it was running OK before I rebuilt the carb, but it didn't want to run right until it warmed up.

  2. #2
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    I would look at 3 things to start

    Fuel pressure
    Float adjustment/needle and seat are correct
    Idle jets and paths are clear

    Good luck

    J

    What you have described sounds like fuel starvation to me.

  3. #3
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    I checked the float adjustments and it was off a little, so I adjusted it to the specs from the rebuild kit. I noticed that the fuel is pooling up to the line in the float bowl now, before it was a little under.

    I was also thinking that I had mixed up the jets or something, but I checked it again and they were all in their proper place. The jets are all numbered so it was easy to identify what went where.

    I am sure that the idle jets are clear as I sprayed all the jets and pathways out with compressed air when I rebuilt it.

    I also noticed that the linkage for the diaphragm on the secondary was loose, I missed putting the e-clip in it before. So I replaced the e-clip. The secondary should work now, in theory.

    After all this, I put the carb back on and its still having the same problem. It seems like the secondary is not kicking in for some reason.

    I'm thinking of taking it to a mechanic if I can't get it straightened out soon. I've been taking off from work so that I can work on it when its warm/daylight outside. But I can't afford to miss much more work.

    :lol:

  4. #4
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    So I brainstormed a little more today, and I'm thinking maybe I have the linkage for the secondary wrong. I've tried it in several different configurations, haven't had much luck with it in any of them.

    Does anyone here happen to have a pic of the B2000 Nikki carb linkage, particularly where the secondary connects? I should have taken pictures before I started tearing it apart :roll:


    My other thought is that maybe I'd be better off buying a Weber than having a mechanic tinker with the stock carb. A Weber is something I'd like to do anyway, it'd be nice getting a bit more power. It is my understanding that the Weber 32/36 would probably add a little more economy as well. I'll have my taxes back soon so now is as good of a time as any.

  5. #5
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    One more question

    Look down into the venturies ,with out the truck running open the throttle to wide open,Do you have fuel squirting out the emultion tubes when the secondarys come in? or at ant point ?

    j

  6. #6
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    I don't think the secondary throttle plate is even opening, it seems to be vacuum activated. I will try to see if any gas comes from the emulsion tubes though. Are the emulsion tubes the ones that are on the boosters and angle down into the venturi?

    Is there a preferred vendor for Weber conversion kits? I am sure thats a common topic on this forum so I'm about to do a search.

  7. #7
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    Yes the exit of the emultion tubes are in the center of the venture, If your secondarys throttle flaps are vacume acuated the accelerator pump should still be squirting fuel down the primarys as you acelerate aggressivley.

    Check with the truck running if the secondarys open when requested.

    Check for fuel squirting out the emultion tubes.

    Sorry i can`t help with a webber vendor.They should be ready available at any auto parts retailer i would think.

    J

  8. #8
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    I found a couple of vendors for the Weber kit. They seem to be going for about $350, which is a steep chunk of change but still about even with the cost of a re-man stock carb.

    I'll tinker with the secondaries when I get home tonight.

  9. #9
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    Maybe this can help you?
    mazda carburator training manual

  10. #10
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    Quote Originally Posted by mazda 818
    Maybe this can help you?
    mazda carburator training manual
    That did help a lot actually. I think it could be that I have the linkage for the secondary wrong. I didn't get a chance to look at it last night to see if the secondary was actually opening but hopefully I will tonight.

    That carb manual is much, much better than the Haynes manual I have been using, or the instructions that came with my carb rebuild kit. I actually took the Haynes back to the store last night.

    I suppose I'll spring for an actual factory service manual once I get my tax refund. :mrgreen:

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