MGB & GT Forum

78 MGB with Weber setup. If you are sitting at idle and try to accelerate, you get a pretty pronounced hesitation. If you feather the gas pedal or back out of the accelerator a bit, you're ok. Very annoying for taking off at a stop sign with oncoming traffic. If I set the idle up from 750 rpm to around 900-1000, it goes away, however I get some dieseling when I shut the car off (which is not present at the 750 rpm setting). I've tried carb cleaner. The hesitation seems to get a little better (maybe it's my imagination) for a little while, but it always comes back eventually. It's much worse when the engine is cold. It nearly goes away after the engine has completely warmed up and run for a while. Any good ideas?

No stranger to this, After replacing my fuel pump diaphragm this problem has went away. My weber idle is about 1000 rpms and runs great, gas mileage is still 23-26 city. Run on..? it did this in the summer but has not since I replaced my fuel pump diaphragm. I was thinking of making a heat shield.

Anyway you might want to check your fuel pressure and give the engine a tune up if its been awhile....

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78..Bee, Leyland A/C (removed), Saturn 95 amp Alternator, Wire Wheels, Lumenition ignition, Weber 32/36, Four speed.

Not the expert on Webers, but both of my MG's have them. In regards to the dieseling there is a anti run on valve for the Weber carbs, they sell for about $17.00. I know some have re jetted the primary and secondary jet, and this has helped solve the stumble.
Ken

Ah Ken I might need one of thoise before the summer do u have a part number?

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78..Bee, Leyland A/C (removed), Saturn 95 amp Alternator, Wire Wheels, Lumenition ignition, Weber 32/36, Four speed.

James
I am searching one out, will give you the info when I get it. But if you go on ebay and look up #280454917188 it is a weber from a BMW and the switch is seen right on front left hand side of the 32/36. I'll keep looking.
Ken

Be sure to check your timing. Mine with the same setup ran really great. One day I decided to mess with the timing. The more I retarded the timing, the more hesitation I had off idle to the point of back firing and really running rough. I set it back where it was and the hesitation went away. Running well again. A lot of carb issues are really ignition issues that need to be sorted out first. Seems to me that a hot engine with bad timing would run better than a cold on with the same time. Matter of temperature to set of the ignition in my mind.

Your idle speed mixture might be a bit rich as well. If the timing isn't it, try to lean it just a bit. Just a thought.

Oh, I see the sensor right next to the acclerator pump housing. duh

The correct name for the switch is the Idle Jet Soleniod. I found the switch on ebay under Weber carbs. Or Item # 280454917188 on sale now.
Ken

Correction item #270458479399 Sorry.....Ken

Still think you should check your timing.

Yes, it could be a number of things.

I had one on my B when I got her, I think it was the 32/36 and it had the same problem. I took it to a MG shop and they couldn't get it to run any better. I bought the manual on them and found nothing there to help. So it was taken off the car with less than 400 miles on it and replaced with HS4's. Hopefully you can figure yours out, I was to leary to drive it with it wanting to almost die everytime I had to come off idle or stop.

Bradly,

Try and post some pictures of your current set up showing vacuum hoses, etc. Maybe someone will see something missing or hooked up incorrectly. Mine was such a great "plug and play" install, I find you issue and others very interesting.

Jon

X2 on the timing. Float level is critical as well. Here is a link for float level adjustments. Good luck.:spinning:

http://www.piercemanifolds.com/Float_Level_1.htm

I installed a Weber 32/36 a little over a year ago and it sounds like "We ber acceleration bog." You may want to re-tune the carb.

You can do this by starting with a warm engine with the choke off.
With the engine shut off.
1. adjust the idle screw until it just contacts the throttle lever, then turn clockwise 1.5 turns.
2. turn the idle mixture screw in until it lightly seats, then back out 2 turns.
3. Start the car it will run rough and you may have to increase the RPMs just enought to keep it running.
4. Turn the mixture screw clockwise 1/8 turn at a time and pause to let the engine adjust.
5. The engine idle will smooth out and you should hear change in the sound of the car when it comes off the main system and onto the idle system. Keep adjusting 1/8 turns until the you see a drop in the RPMs, then turn counter clockwise a 1/16 of a turn.
6. Set the idle speed back up to 900 RPMs. Take it for a drive...see if the bog is gone. If not you may have to repeat the process.

I was not able to get my Weber off of the main system and ended up shortening the spring on the idle mixture screw. It has been running great since with average MPG at 26 town and highway.

hope this is helpful,
mike