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Thread: weber carb trouble

  1. #1

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    weber carb trouble

    Hey y'all I've got a tricky situation that I need some help on before it kills me. I put a Weber 3236 on my 2.6 MMM 3 weeks ago when I couldn't pass the emissions test. It ran great until today. I was driving up a 3 mile steep hill in 2nd gear at about 3/4 throttle when it suddenly stuck. I pulled over and checked out the linkage and it was fine-returned to normal idle position and no sticking in the throttle cable. I managed to nurse it home by alternating coasting in gear with ignition off and power on in a higher gear. Removed the carb, took off top cover, everything looks clean, good and normal. Checked movement of all parts-accelerator pump, choke, and throttle with same result-working fine. I installed the carb and fired it up, idling about 3500 still. I covered the air horn with my hand and idle drops with less air, but I noticed gas atomizing in the secondary constantly. I have the stock fuel pump and no pressure regulator per the Weber rep's recommendation. Any ideas on what would cause this? Is my fuel pressure too high? Am I taking fuel off of the wrong outlet from the pump? I checked out the pump hoses when I did the initial install and am pretty sure I got the fuel return line done correctly. I can't understand why it would run flawlessly for 3 weeks and then suddenly go into zombie mode. I've have tried for 3 weeks to contact the weber help line about another issue with no success so I'm pretty sure that's a dead end. Can some one direct me to a solution please? thanks

  2. #2



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    Somthing is holding the throttle open. Cable is sticking or somthing is holding the butterfly open.
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  3. #3

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    but the throttle is closed like normal. I disconnected the cable to make certain it wasn't the issue. gas is dumping into the secondary somehow. I'm wondering if some gunk got through the filter and got stuck in some part of the main float area.

  4. #4



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    Ya it's possible that some crap got into the needle and seat. But it should be running real rich and black smoke out the tail pipe, not high rpm. Is the throttle stop sitting in the adjuster screw? Or is there a gap?
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  5. #5



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    The stock manual fuel pump is overpressurizing the needle and seat, forcing fuel past it at idle. Take a close look at the needle and seat - the needle will be deformed and not seal to the seat. You may have also blown out gaskets inside the carb, causing other paths for fuel that are uncontrolled. A rebuild of the carb will be necessary, and a proper electric fuel pump will solve the problem you are having.
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  6. #6

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    Thanks guys. Any ideas on correct fuel pump? Maybe a Holley #12-804? And will it need a pressure regulator also? Thanks a lot for the help.

  7. #7



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    I think it's 4 - 7 PSI is all it needs. Look in the weber manual. It will tell you. There is one in the manual section under the first gen factory manual. I have one in there.
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  8. #8

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    thanks again

  9. #9



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    Be sure to mount it as close to the tank as possible - it is a pusher style pump and cannot draw fuel well if mounted in the engine compartment. Check out the various threads on here for all the particulars. Geronimo has been running with an electric pump since 1983. Keep in mind that the weber works better with a high flow rate pump even more so than higher pressure.
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  10. #10

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    I really appreciate your help. Hopefully I'll have this all sorted out today.

  11. #11

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    Final update-problem solved. Incredibly it was "none of the above" for the problems and solutions. It was an adjusting screw for the secondary butterfly-it was loose and vibrated itself loose enough at WOT to idle at 4000 rpm. I took it apart today with intent to replace what I thought was the broken part and realized what had happened. So I adjusted it correctly, this time with Loctite thread locker, installed it and it runs like a champ, with the stock fuel pump. Thanks to all for your help. I've attached two photos to illustrate. So, if any of you that have a Weber 3236 installed on your ride ever experience an extremely high idle for no apparent reason, check to see if the secondary butterfly is closing completely at idle.
    Click image for larger version. 

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ID:	3965Click image for larger version. 

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ID:	3965

  12. #12

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    Final update-problem solved. Incredibly it was "none of the above" for the problems and solutions. It was an adjusting screw for the secondary butterfly-it was loose and vibrated itself loose enough at WOT to idle at 4000 rpm. I took it apart today with intent to replace what I thought was the broken part and realized what had happened. So I adjusted it correctly, this time with Loctite thread locker, installed it and it runs like a champ, with the stock fuel pump. Thanks to all for your help. I've attached two photos to illustrate. The first one shows how far open the butterfly was, and the second shows how high the screw was. So, if any of you that have a Weber 3236 installed on your ride ever experience an extremely high idle for no apparent reason, check to see if the secondary butterfly is closing completely at idle.
    Click image for larger version. 

Name:	secondary.jpg 
Views:	120 
Size:	46.2 KB 
ID:	3965Click image for larger version. 

Name:	screw.jpg 
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ID:	3966

  13. #13

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    sorry, can't figure out how to edit or delete a post

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