Weber question

teachkenpo · 04-06-2006, 09:35 PM

Hi, I am working on adjusting my weber 40 ida's on a 2.0 motor. The info I have been able to find says it should squirt .6 to .8 cc per actuation. I can only get .4 even though I have adjusted the arm as long as it will go. Any suggestions how to increase the cc output?
thanks,
John

duckmcf · 04-06-2006, 10:14 PM

Hi John,
I think the arm that you're referring to is only for light adjuctment / tuning purposes. To significantly change the output you'll need to change the pump jet.

RoninLB · 04-06-2006, 11:02 PM

does it stumble ?

teachkenpo · 04-07-2006, 12:07 AM

Hi, yes it stumbles when it hits about 4k under full throttle. I am thinking I am not dumping enough gas into it.

RoninLB · 04-07-2006, 03:44 AM

So then if you're in 3rd gear at 3.5K rpm and whack it it'll stumble after climbing a bit at 4k rpm ?

Or if you're in 3rd gear and wack it at 4k it'll immediately stumble ?

teachkenpo · 04-07-2006, 05:33 AM

If I do a strong exelleration it will stumble even in first. It sorta shuts down like it ran out of fuel. Almost feels like a governer.

captainrb · 04-07-2006, 08:52 AM

I have been told that Weber's will have a stumble/hesitation between low speed circuit and the high speed circuit.Not bad but anoying. the RPM at which it goes from low speed to high speed can be altered my changing idle jet and/or the main jet. I've fooled around with it but still remains. I just nurse it through the cross over and no other problems.

Netspeed · 04-07-2006, 09:59 AM

Here's something interesting that happened last weekend that is like your problem:

Some friends were running their Alfa 2.0 at the track and the thing stumbled but more at higher rpms....they went through everything. Replace all the high-voltage ignition stuff and then ruled that out. They changed the jets and eventually removed the carbs to inspect. Nothing wrong....guess what it was? A poor ground at the coil. Although it was bolted to the firewall, it was corroded enough that a the system produced a weak spark.

avendlerdp · avendlerdp's Garage

Try a test where you ease it up to high RPM under load. Go about 30 and put it in 3rd and ease it up to 60. If it stumbles when you are barely moving the gas pedal you have a different issue.

Remember that most driving on Webers is done on the idle jets. If you have an issue at the transition, you may have some dirt in the bowles and a clogged main jet.

Will it go to redline?

Alex

Netspeed · 04-07-2006, 12:46 PM

Also, check to see if you have a nice big blue spark coming out of the end of the plug wire.

jwetering · jwetering's Garage

Quote:

Originally posted by captainrb
I have been told that Weber's will have a stumble/hesitation between low speed circuit and the high speed circuit.Not bad but anoying. \

FWIW I've never been able to detect the transition between the idle and main circuits. Before I got the carbs three years ago I was worried about a "dead" spot. Suprised the heck out of me when I actually started driving the car. It was and still is absolutely seamless from 1000 to 7000 rpm.

That said - I have run into a situation you describe, and it took a fair bit of teardown to find the root cause. Turned out that bits of the o-rings around the mixture screws had found their way into one of the emulsion tubes, and one of the main jets. The car idled fine, but when it hit the mains it would stumble. I chased that for a while, even installing a new fuel manifold (nice PMO system BTW) since I thought I was running out fuel under full throttle. The same o-rings plugged off an idle jet once too, but that time it caused a distinct miss at idle and low revs.

Needless to say, I don't use o-rings around the mixture screws anymore.

Good luck with your problem. It is fixable.

teachkenpo · 04-07-2006, 05:31 PM

Quote:

Originally posted by avendlerdp

Will it go to redline?

Alex

No, it won't go redline. I can't get it over about 4700. I have just totally rebuilt the carbs, and they are put together properly and spotless. The only other thing I did was replace the idle jets from .055 to .060. Yesterday it was worse, and I added washers to the float valve to to fill the bowls more. Today, it is a little better, but still bad.

RoninLB · 04-07-2006, 06:27 PM

maybe fuel pump is on its way to kaput ?

otherwise it's pretty hard to detect the transistion.. generally.

My transistion starts coming on [4th gear] around 3.2k with the mains mostly taking over by 3.8k. A single digital and bar graph EGT ga is great entertainment and an tuner's dream. Some pelicanheads attempt to adjust their carbs with Pelican's $300 O2 meter contraption. I forgot the name?

911pcars · 04-08-2006, 12:30 AM

I vote for suspected fuel pump as well.

The engine needs fuel, air and spark. Without one or more, engine will not run.

Sherwood

SteveF_911 · SteveF_911's Garage

teachkenpo

I just spent a few hours yesterday working on Weber's on my 2.0.

On the idle jets I fin 55 a little big I prefer a 50.

Check all your spark plugs, try and determine if all cilynders are running the same. If the plugs are black then you are rich.

From what you are telling us you think the car is not getting enough fuel on the main jets. Could be a fuel pump or it may be something in the carbs.

If you have just rebuilt your carbies check that the Aux Venturies are not in upside down this will give these symptoms.

Also check it is not a ignition problem.

Good luck carbs can be a real ***** when they play up.

teachkenpo · 04-08-2006, 05:08 PM

Well, I am away until monday, so I will have to wait until then to work on it a little more. First thing I am going to do is swap fuel pumps, and if that doesn't work, I will change the idle jets back to 55. If that improves it, I will order some 50's and see if that improves it also. All the suggestions are very helpful. Thanks to all who responded. I will update when I have more info.
John

RoninLB · 04-09-2006, 12:02 AM

Quote:

Originally posted by jwetering

That said - I have run into a situation you describe, and it took a fair bit of teardown to find the root cause. Turned out that bits of the o-rings around the mixture screws had found their way

good story.

I've had flakes off a gasket make me nuts.

teachkenpo · 04-11-2006, 11:06 PM

Update!
Hi, here is where I am in the diagnostic process.
I changed the fuel pump - No improvement
I changed the idle jets back to .055 from the .060 - No improvement
I added washers to the float bowl valves - No improvement

So I still have a car that stalls and sputters when it hits near the 5k mark. Any other ideas?
thanks

deanp · 04-12-2006, 06:27 AM

Not familiar with what the 2.0's are using to regulate the fuel pressure. What do you have for fuel pressure?

What are you using to regulate it?

When was the last time you changed the fuel filter?

Where in MA are you?

teachkenpo · 04-12-2006, 06:31 AM

Quote:

Originally posted by deanp
Not familiar with what the 2.0's are using to regulate the fuel pressure. What do you have for fuel pressure?

What are you using to regulate it?

When was the last time you changed the fuel filter?

Where in MA are you?

Hi, the fuel pressure is running at about 3.5-4 psi. There is no regulator. It is using the factory fuel pump. The fuel filters are all new. I am in the springfield area. Thanks,
John