BeMyWay

Weber 32/36 Bogging On Initial Acceleration

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I have recently install a Weber 32/36 carbureator on my 1983 BMW 320i (e21) 1.8L engine and it bogs every time I try to rev the engine from idle.  

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Back story...I removed the  K-Jet (mechanical fuel injection) from the car because it would have cost me more to repair than I paid for the car. 

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So now it is running and idling great, but it will not respond immediately with initial throttle.  It make a throaty air intake sound.  if you do not release the throttle, the engine will backfire and die.

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The intake and manifold came from a 2002 I had.  I rebuilt the carb.  I have checked and do not have vacuum leaks.  

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Also, the jets were cleaned and are primary 165 and secondary 160.

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Also, if I run this screw (in the red box) all the way in, the car will not run.  In all the data I have found so far says to screw it in all the way.  So for the time being I keep it screwed out to keep it idling.

Carb 1.JPG

 

Anyway, if you have any suggestions, I would appreciate any help.

Thanks

 

Edited by BeMyWay
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Your idle jet (at the bottom of your pic) is screwed way in, I notice...

 

When you, with the car off and the choke plate held open, open the throttle, does the carb squirt a jet of fuel down the

smaller primary barrel?  It's supposed to...

 

t

 

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I looked and what do you know...no spray.    Are you saying the idle mixture or idle jet screw is way in?  I will run out the idle mixture screw first and see if she will run.  If after adjusting these screws and she does not spray, I will break the carb down tomorrow and look for blockage.

 

Also, on the image below, what is the correct setting for the Idle Jet screw (3a)?  Should it be all the way in (seated) or adjust to make it idle better.  If I run the idle jet screw all the way in, the engine will not idle and dies.

weber-carburetor-adjustment.jpg

 

Thanks.

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The Idle jet screw and mount 3a should be completely tight - snug   It should not be loose and sucking air.

The idle mixture screw 3b should be  abpout1 and 1/2 turns out of a light seat as a starting point  May take more or less depending on how close your primary jetting is to the needs of the motor

165 may be a little rich for a stock 1.8 engine  If you can get it to idle down to 500 rpm them set the best idle possible with 3b Next adjust the idle speed to 900 rpm

The second big issue is to be sure the throttle linkage is nor overly tight on the Linkage adapter and binding the linkage  or preventing the throttle butterfly's to close completely . Back this off from tight, use some Loctite and bend the lock washer in place on a flat surface of the linkage connector 

If you don't get a spray of gas  when opening the throttle,   then suspect the accelerator pump.  Check your linkage to be sure it's connected

A Stumble you describe  is most likely  an accelerator pump issue 

Download the tuning instructions from Redline and follow them religiously.  The jetting is very important to getting the Carb to run right. the instructions will tell you which way to go with jets based on how it acts in the proper adjustments. 

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The symptoms and lack of spray say that this is a pump jet issue. Fix that and then follow the 'lean best idle' technique above. The trick is to get it idling well with the minimum throttle opening to keep it on the idle jet and not the transition. 

 

Just out of interest, what are you using for ignition?

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Interesting...my idle jet does not have a screw mount.  I will snug it down and see if I can get it to run.

Thanks 

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6 minutes ago, Simeon said:

Just out of interest, what are you using for ignition?

 

I am using the stock electronic ignition.  

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It sounds like you have a chunk of junk in there somewhere.

 

The test Toby had you do was to see if the accelerator pump was doing its job and providing that squirt of fuel. 

It has a diaphragm which could be punctured, but it is probably not.  This is that diaphragm and the 

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It gets fed fuel from the bowl by passing through an orifice, around a brass threaded pin, which you should unscrew from the top, to make sure it is clean and clear in there.  Corrosion happens between the brass and carb body, causing white powdery buildup, which caused it to get plugged up.  that hole at two oclock is the one the pin is in, in this photo.

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The pin is the one on the left in this photo and the accelerator pump feeds fuel through the thing at the top, which should be removed and the parts and passages cleaned.

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The jets you are referring to as 160 and 165 are actually the air correctors.  They sit on top of the emulsion tubes.  You should pull them out and remove the tubes to make sure that area is clean and clear as well.

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make note of which emulsion tubes/jets are installed and make sure they go back in the same holes (sorry for stating the obvious).  

 

I think your rebuild did not go deep enough, in terms of removal/cleaning.  That is where I would start.  It will not run well at all, without that visible squirt of fuel from the accelerator pump.

 

Those two things that bridge the throats are called the auxiliary venturis and they need to be a snug fit, with the side that has a hole matched to the side with a hole.  In other words, they can be installed backwards.  If they need shimming, I found that a shim cut from a beer can worked well, at about .004".

 

Time to pull it out and open it back up... imho.

 

 

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'76Mintgrun'02...thanks for the pictures...I'm on it.  I need to do the same for a 1976 '02 I'm about to pick up.  All this information is what I need!

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The stock electronic ignition (I am not that familiar with K jetronic) uses mechanical advance and a vacuum advance capsule?

 

When you get your car running check the operation of both with a timing light. You might need to advance your initial timing to suit the carb but you then need to worry about what the maximum advance would be. Not sure of the specs for that distributor but you may be better timing it based on a maximum safe advance (say 34 to 36 degrees) at whatever enginespeed the maximum advance is all in at (say 3000rpm). 

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I took the carb partially apart and found the accelerator to be okay.

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What I did find was the primary jet was not allowing fuel to pass through.  I use a guitar string to route it out and it finally began to squirt fuel...

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I took it for a test drive and it drove nicely...I still have to tweak the mixtures and check the timing again...tomorrow is a good day!

 

Thank you all for your IMMEDIATE help. 

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Good job and thanks for the immediate update.:)

 

(timing before carburetor adjustment, when it comes to fine tuning)

 

 

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On 8/17/2016 at 1:51 AM, Simeon said:

The stock electronic ignition (I am not that familiar with K jetronic) uses mechanical advance and a vacuum advance capsule?

 

When you get your car running check the operation of both with a timing light. You might need to advance your initial timing to suit the carb but you then need to worry about what the maximum advance would be. Not sure of the specs for that distributor but you may be better timing it based on a maximum safe advance (say 34 to 36 degrees) at whatever enginespeed the maximum advance is all in at (say 3000rpm). 

 

I'm looking into the timing specs and will tweak it with using the carb settings and the seat of ye 'ol pants...thanks.

 

 

9 hours ago, '76Mintgrun'02 said:

Good job and thanks for the immediate update.:)

 

(timing before carburetor adjustment, when it comes to fine tuning)

 

 

 

Thanks for your help (and all others also).  Great advice about the tuning.  Sometimes the scheduling of the fixes is just as important, or more so, than the fixes.

Take care.

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Does this Idle Jet screw need to be screwed in snugly?  When I screw my all the way in, the car speeds up then dies and then will not restart.  If I back it off a 1/4 to 1/2 turn she runs fine.  It starts now without any priming...however, I think the jets are too big, because she is running rich at idle.  I am looking to purchase smaller jets and see how that works.   

 

Please let me know if there is anyone with some smaller jets that they want to sell.

Take care.

weber-carburetor-adjustment.jpg

 

Carb 1.JPG

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Is that photo of your Weber?  If so, have you connected the cable to the choke, or is it free to move around?

 

The idle jet cover screw should be snugged down.  Is the jet clean?

I ordered new jets to use c.d.'s prescription, for the 32-26 and it seems to be working well on my engine.

Soon, I will install the AFR and see how it is really doing.

I think I ordered my jets from Carbs Unlimited, because they are just across the water in Seattle.

What size jets are you running now?

 

I see two hoses coming off the vacuum nipples and assume one is going to the distributor (top one), but where is the other going?  Is it plugged?  (again, is that photo of your carb?)

 

Sorry, more questions than answers from me.

 

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