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Need advice from the Weber gurus
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whale
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PostPosted: Tue Aug 11, 2020 9:35 pm    Post subject: Need advice from the Weber gurus Reply with quote

One side of my Weber IDF 40 is not working at all. I can pull the plug wire for that cylinder and there is no difference. There is spark, however, my fuel pressure is a steady 3.5 lbs and my valves are set correctly. The plug itself remains clean (not fat, not lean. Clean as in not getting any fuel).

So far, that seems like a somewhat typical issue. Hereís where it gets weird...

I have cleaned the carb multiple times. It is spotless. I can also spray carb cleaner in each hole and it emerges from the right places on the carb. From what I can tell by matching up the amount of carb cleaner gushing out of the good side of the carb with the bad side, both idle circuits seem to flow identically. I can even pour fuel in and see it coming out of the four holes just above the butterfly.

I switched carbs from one side of the engine to the other and the problem follows the bad barrel within the carb.

Going one further, I also swapped jets, air mixture screws, and all other internal items on the carb. Floats are set correctly, too. I bought and installed a new idle jet just to make sure.

I checked for vacuum leaks and there donít appear to be any.

The issue still remains on that specific side of my carb while the other half works fine, as does the opposite IDF. Despite my best efforts and several full-fledged cleanings. It is as if Iím not getting any fuel through that one side.

If I spray starter fluid down the faulty barrel the engine comes alive.

Iím at a loss. Any suggestions on what I should try next?

Thank you in advance.
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madmike
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PostPosted: Wed Aug 12, 2020 3:49 am    Post subject: Re: Need advice from the Weber gurus Reply with quote

If your just using carb spay to clean it's not enough pressure to get to crap out , ,complete disassembly and hot tank it Wink blow out with High pressure air
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modok
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PostPosted: Wed Aug 12, 2020 4:32 am    Post subject: Re: Need advice from the Weber gurus Reply with quote

You have overlooked something
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whale
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PostPosted: Wed Aug 12, 2020 9:11 am    Post subject: Re: Need advice from the Weber gurus Reply with quote

I used air to clean the carb.. I also soaked the carb overnight so it is very clean.

I agree that I must be overlooking something, but having swapped out all parts within the carb and having ensured everything is adjusted right, I have no clue what the issue might be. Thatís why Iíve come to the forum for help.. Very Happy
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whale
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PostPosted: Wed Aug 12, 2020 12:59 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

I should add that after cleaning the carb for the umpteenth time I ran a very thin (.09 inches) guitar string through all of the passages to ensure all of the ports and passageways are clear and not clogged up.

And yet, I'm still not getting any fuel to run through that specific side of the carb and into the cylinder.

Sigh....
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Ohio Tom
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PostPosted: Wed Aug 12, 2020 1:19 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

Few questions:

Did you take the butterflys out? if you did, are you sure you got them properly re-located?

Have you adjusted or removed the air bleed screw (next to the mixture screw) at the base of the carb?

Have you torqued on the nuts on the end of the shaft?
If so, how did you hold the shaft?.

If you held the shaft on one end and torqued the other, you can easily twist the shaft, thus creating a big change in throttle plate position.
I Have seen this on carbs that folks have tweak the nuts on.
You can find this by measuring the position of each butterfly with a caliper or other tool. If you find a twist, you know that's the issue.

I usually fix this by twisting the shaft the other way using 2 small adjustable wrenches.
How much? I usually setup the motor on the test stand and have it running. Then I can give a twist, then hear if that cyl is coming back. If not, twist more, check again.


Sometimes crap can sit down in the bottom of the " Jet well" and lift up and plug the jet only when running. Shut it off and it falls to the bottom.
Dellortos are famous for this.
Lots of compressed air and a long nozzle is good to have...
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whale
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PostPosted: Wed Aug 12, 2020 2:05 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

Hi Tom,

Thank you very much for your reply!!

I haven't had the butterflys out myself, but the carbs are used so there is a chance that someone has removed/replaced them before me. Both butterflies close tight against the side of the walls, but I'll check on the measurement of both butterflies just to make sure everything is right.

I have the air bleed screw all the way in. I pulled it out (a few times) while cleaning the carbs. I read that the air bleed helps when syncing up the various barrels, but does little once the main jets come into play.

I synced up the three working cylinders/barrels using the other air bleed adjusters, but couldn't do much with the non-functioning barrel. My "snail" was showing a pull from the intake though.

I tightened the nuts on the shafts by holding the throttle arms (i.e., the piece that connects to the heim joint). The nuts are snug enough to hold the throttle arms in place and the retaining washer is folded over to hold everything in place, but the nuts are not tight enough to bind or distort the shaft. The shaft bearings seem to be fine, too. No apparent vacuum or fuel leaks from that area.
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PostPosted: Wed Aug 12, 2020 2:11 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

this may very well not be your problem, but it happened to me once so ill share..

I had the same situation, one cylinder not firing and the plug was clean.

turns out one of the enrichment plungers got stuck open dumping a TON of fuel down that cylinder, so much so that it wasn't firing at all, hence the plug staying clean.

do your carbs have the enrichment circuit still? or are they much newer models that have this feature completely omitted?


if you have proven that you have strong spark in that cylinder, then its a simple case of not enough fuel, or too much fuel. gotta track it down!
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PostPosted: Wed Aug 12, 2020 2:26 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

Had a curious adventure some years ago...

A friend of mine got a new pair of spanish IDF's out of the box and had almost the same issue, enough fuel at idle but almost none at one barrel at acceleration or load.

They searched a long time, interchanging the carbs, setting float level and so on.

To make this long story short, one of the mains was not drilled through....


Another crazy mistake:

A friend lost a closing plug for the idle/bypass-bores and simply took a screw of the same thread in. Unfortunately the screw was longer than the former plug, closing all bypasses. This was an easy car to tune...



What I want to say:

You have to check almost everything, every bore, jet, plug, set screw and so on to bring the carb back to work.
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whale
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PostPosted: Wed Aug 12, 2020 3:30 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

Thanks for your suggestions VeeDee.


I became soooooooo sick of pulling that carb to test, then clean, the test it again that I went through every possible orifice (even the bolts holes!!) to make sure it is spotless and every port flows freely.

I swapped all of the internal parts from the working carb to the half-functional carb. That included all of the jets, floats, etc.

I am at the point now where I'm beginning to think there is an issue with the bottom frame of the carb itself. That is the only item that has remained constant.

If anyone has a Weber IDF 40 carcass lying around, I would be very interested in rebuilding it with my wonky IDF.
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modok
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PostPosted: Wed Aug 12, 2020 5:05 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

How does the fuel get from the float bowl to the idle jet?

How does it get from the idle jet to the progression ports?

What size are the holes?
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whale
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PostPosted: Wed Aug 12, 2020 5:09 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

This is a great video that offers a thorough explanation of the Weber IDF idle circuit. The presenter, Vic Ferarri, shows the path for the fuel, the manner in which the air is mixed with the fuel, and the most common places where clogs can happen. He also explains how to clean the carb properly should you have an issue with your idle circuit. It is well worth watching.

I have gone through my idle circuit from top to bottom.



Link
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PostPosted: Wed Aug 12, 2020 5:13 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

time to invest in that ultrasonic cleaner you've always wanted Wink once you have one you'll never go back...

ive got this one, you can find em cheaper if you look harder than my 5 second google search. https://www.ebay.com/i/263302250036?chn=ps&nor...600ebb1d63

of course, you still have to wipe the carb down, and make sure you've got all the junk out w/ compressed air, but this will work 10x better than splitting old wire into individual strands and trying to poke em in passages w/out bending em Smile i also use my unit for just about everything i can fit into it. if you have the money, buy the largest one you can afford.
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PostPosted: Wed Aug 12, 2020 5:20 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

If YOU know where the fuel path is, then you can find the ERROR in the video, as it relates to your carbs
Wink
Passage must pass, plugs must be plugged, and jets must be the right size. So simple yet YES it can fool you. but if you want us to check your work, you have to show your work.
If you traced the passages and identified all the plugs Ok, I can take your word for it, but...... you could also tell us what you found and we could check that it's right.
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whale
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PostPosted: Wed Aug 12, 2020 6:20 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

I am not a pro when it comes to Weber IDFs. The fellow in the video certainly knows more than me so I went by his advice and experience.

If there is an error in his video PLEASE let everyone know so that we can all benefit.

As for what I found with my carbs... the passages for my idle circuits are absolutely, positively clean. There is zero doubt about that. I can blow air through them, I can pass a large volume of carb cleaner from one end of the idle circuit to the other end, and I can run a very thin wire all the way through it, as well. In every way that I can bench-test the two carbs, they appear to be identical.

Likewise, I swapped everything (jets, floats, gaskets, top cover, etc...) from my working IDF over to the non-functional IDF. Literally everything that could be removed (except for the pressed in plugs) was swapped.

I checked out the seating for the air mixture needles with a high powered military magnifying glass. It's difficult to tell for certain because the hole is extremely small, but there doesn't seem to be anything causing a problem there.

I also checked out the internal seating for the idle jet (where the tip of the jet presses into the body of the carb. That, too, appears to be fine.

And yet, the issue remains.

I'm not sure what more there is for me to check. That is why I have come "hat in hand" asking for help from those on the site. I am defintely not trying to be obstinate or ungrateful and I am willing to check and double check whatever anyone suggests. I'm just totally at a loss.
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whale
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PostPosted: Wed Aug 12, 2020 6:33 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

Following up on an earlier suggestion, I just checked the butterflies. I shone a flashlight from the top and also from the bottom of the carb. There is no light passing by the butterflies. They are sealing tight against the edges of the carb.

I don't if there is an official way to test the shaft, but I wiggled the butterflies back and forth and up and down. There is no movement to and fro in the shafts or the bearings.
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PostPosted: Wed Aug 12, 2020 7:14 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

Ok....at 7.25, he points to where the drilling would be if it was in the main well, and says "that's below the main jet". no
Actually the carburetor body casting is designed so that it can be drilled either way. And in HIS carburetor, it is 1/2" below where he is pointing.

the idle feed is either below the main jet, OR into the main well, depending on which passage is drilled.
You can look at the outside of the carburetor body and see bosses for both. the one that is drilled has a plug in it and the other will be blank.

In all models of 40 idf that I have seen, the idle feed is from the main well. the actual hole in the side of the main well is a calibrated size, and I'm glad you didn't ask what that size is...... because i don't remember. but the fact that that passageway only has a small hole into the well does make it more likely something can get stuck between that and the idle jet.

if it WAS a leak, it would have to be above fuel level because it doesn't leak/flood....
far as plugs which could be missing or leak, that would be the plugs in the carb base, and by the idle air bleed, and outside of the carb.

if the carburetor casting is porous and that's the air leak, maybe it IS something not worth fixing, but there is no voo-doo going on, it's just plumbing and calibrated holes. So, fix the plumbing and calibrate the holes, and it WILL work.
I have seen defective carbs. My favorite was a solex with a plugged passage..... found a broken off drill bit in there.....just another day at the carburetor factory, I wonder where that drill bit went? Laughing
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PostPosted: Wed Aug 12, 2020 9:38 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

I use a sharpie on the jets to check if they seat. Maybe you used too much air and dislodged a plug. Put some sealant on all of the plugs and see if it helps. I had one that leaked. Put a dab of jb on it. If it runs fine off the idle circuit, that helps to narrow it down.
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PostPosted: Sat Aug 15, 2020 8:00 pm    Post subject: Re: Need advice from the Weber gurus Reply with quote

Also make certain your aux vent is not upside down and the top gasket is not plugging any of the small ports.
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