Jump to content
downhillwolf

Weber DCOE 40 problem

18 posts / 4767 viewsLast Reply

Recommended Posts

Hi, im having a problems with my dcoe's.

There is a problem, after rebuilt and ultrasonic bath i couldnt make them sync so they could run steady.

So i went to a shop for carburator adjusting. The worker did try to tune my dcoe's and still they werent steady at idle. So he put my car on tester to test my exhaust and oil pan gases. Oil pan was ok, so there was no gases escapig behind pistons.

But in the exhaust he did find massive amount of unburned gases.

After more detailing we found out that some idle screws didn't make engine correspond to cut the fuel off.

So there sould be a leak of fuel comming from somewhere.

I did check all canals, and all nozzles.

I did also remove choke mechanism and make choke pistons cone and inner edge too. So they must perfectly fit so no fuel could pass by.

I don't know what else should it be.

Does anyone have any clue? Any similar simptoms and did make it right?

Share this post


Link to post
Share on other sites

Float level and needles come to mind. As does fuel pressure.

And a lot of other things.

Look at the theads that Fred73tii posted a week or 2 back about his

DCOE's and go through all the suggestions there.

It's pretty comprehensive.

t

Share this post


Link to post
Share on other sites

That thread starts here:

Need DCOE help, loss of power on track (long)

http://www.bmw2002faq.com/component/option,com_forum/Itemid,50/page,viewtopic/t,376777/

The saga continues here:

Need DCOE Help, odd Synchronizer readings

http://www.bmw2002faq.com/component/option,com_forum/Itemid,50/page,viewtopic/t,377302/

and ends here:

DCOE Help Update: Problem Solved

http://www.bmw2002faq.com/component/option,com_forum/Itemid,57/page,viewtopic/t,377659/

Unburned gas could mean either a very rich mixture, or lack of spark that results in unburned fuel, which could even happen with a lean mixture. The first step is figuring which system(s) are affected: fuel delivery to carbs, carbs themselves, ignition, other electrical, internal engine issues, manifold issues, etc. It took me a number of weeks to solve my problems, I believe there were multiple issue but I changed so many things at once in the beginning that it is hard to know what they were. So, if I learned one thing, it is really do just change one thing at a time.

Fred '73tii & '69GT3

Share this post


Link to post
Share on other sites

Usually If the idle mixture screws do not respond to adjustment you have the

idle speed screw to far open and are on the the first progression hole. Make

sure when you start the tuning process have the speed screw just barely

cracked. The idea is you want to have the throttle plate open enough to

cover the first progression but not so much as to expose any of it to engine

vacuum. If you have carbs that you can remove the progression cover

you can look down the hole and see were the plate is in relation to the first

hole. Shine a light down the stack and you will see it. Center the plate over

the first hole for best performance.

Make sure you have no vacuum leaks too I have seen a lot of cars that

were running rough and the line from the brake booster to the manifold was

leaking air. The key to getting the best drive ability is setting the idle speed

screw , idle mixture, and idle jet just right. They all influence each other.

Share this post


Link to post
Share on other sites

Thanks i will read.

I have my carbs as closed as they could be, so progression holes are not on the force of vacuum.

If i close the idle screws still engine makes no response as on other 3 idle screws. Floats are measured to have both 25g and the gap to full close the income petrol valve is 8mm as specified in book. Also valves for petrol incoming are tested and working fine. Fuel pressure is not too much, because i have crossway after mechanical pump for the fuel tank and one is going to the filter and Fispa pressure valve from ferrari and then on on carbs. Pressure valve is adjusted to 3psi and this procedure is because of mechanical pump is from 6-cyl engine and have more flow and power than normal pump on 02.

When engine is reving all cylinders are adjusted fine, i have only problem at idle and few rpm's above it. Somewhere is leaking fuel because if i close the idle screw at cly1 nothing hapens, and on the other 3 there is response to almost engine die. Valves are adjusted corectly, and compression is the same in all cyl.

I have have daubts in choke valves to have fuel leak, as they were changed during cleaning and asembling. So i make them again cone, and also zhe edge inside choke valve limiter to make them fit as much as i can. But no change was done...

Any other clue?

Share this post


Link to post
Share on other sites

What chokes are installed ? & what are the jet sizes ? we need information.

Share this post


Link to post
Share on other sites

bent throttle shaft, is my guess, if the starting circuits really are sealing.

t

Share this post


Link to post
Share on other sites
bent throttle shaft, is my guess, if the starting circuits really are sealing.

t

Throttle shaft is not bent, and closes the same amount of air as working one.

Starting circuts? These are probably choke pistons?

I probably sealed them, but dont know how to make sure they are sealed for sure(cannot make so much vacum to really test them).

Share this post


Link to post
Share on other sites

I did also remove choke mechanism and make choke pistons cone and inner edge too. So they must perfectly fit so no fuel could pass by.

A slight detour on the topic at hand...I want to remove my choke mechanisms (cold start unit) as well (45DCOE9) and install block-off plates. Are the cold start jets and cold start valve assemblies left in place or removed when this is done? Do I need just the cold start block off plate, or an entire kit?

Weber DCOE Cold Start block-off plate (99005.135)

http://www.piercemanifolds.com/product_p/99005.135.htm

http://www.iemotorsport.com/bmw/2002-fuel-intake/DCOEbop.html

Weber DCOE Cold Start (choke) Elimination Kit

http://www.weberperformance.com.au/product_info.php?products_id=845

If someone could point me to the correct procedure that would be great.....sorry I can't give insight into the carb tuning issue here.

Fred '74tii & '69GT3

Share this post


Link to post
Share on other sites

@ FB73tii

You got email on that manner...

If anyone knows what should be wrong i would much appreciate.

Share this post


Link to post
Share on other sites

Those all sizes are good, because all this 2 sets of Webers were instaled on 2002 25 years ago, then tey were laying ever since (too much fuel consumption for daily).

Share this post


Link to post
Share on other sites

The starter circuits are the little plungers that are lifted by the

'choke' cable.

It's possible for the cheezy stamped steel 'lifters' to get bent,

and then the pistons inside don't drop all the way down to seal.

If you take the cover off (with the linkage and 'gears' attached to it)

then the pistons should drop all the way, guaranteeing they're closed.

Unless one's stuck...

Since 3 of 4 seem to be working, that's about the only thing

that can bypass the throttle plate.

Oh, unless the bottom of the throttle plate's bent. Or filed.

(it's an older tuning trick)

t

Share this post


Link to post
Share on other sites
The starter circuits are the little plungers that are lifted by the

'choke' cable.

It's possible for the cheezy stamped steel 'lifters' to get bent,

and then the pistons inside don't drop all the way down to seal.

If you take the cover off (with the linkage and 'gears' attached to it)

then the pistons should drop all the way, guaranteeing they're closed.

Unless one's stuck...

Since 3 of 4 seem to be working, that's about the only thing

that can bypass the throttle plate.

Oh, unless the bottom of the throttle plate's bent. Or filed.

(it's an older tuning trick)

t

Cold start or choke mechanism is removed.

Throttle plate s not bent and can seal the hole like the other one...

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.




×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.