Hi Michael,
Bubbles in fuel line are nothing to worry about- don't be scared to have a go at the carburettor as they are a pretty simple device.
One other thing to check is that the carburettor top cover gasket is the correct way up- it is possible to put it in upside down which can block some passages and expose others that should be sealed. There is a locating pin that makes it easy to work out.
Good luck!

Any chance of a video of the car idling?

It's always difficult diagnosing problems from a distance and any extra information helps.

Chris

Okay, so here is the latest on my adventure to get Christine's car on the road. As previously stated I have done many different things to try to solve my problem. My latest discovery is that there is a hole in the drip tray below the carburetor and though it does indeed look like it belongs there if I plug said hole I can idle down and have a backfire free idle around the 800rpm mark. Does that info narrow down anything for you guys? Once again I would like to thank all for the help. I have already learnt a lot though barely scratching the surface.

P.S. I did take apart the carb and blew compressed air though everything. There was quite a bit of crud at the bottom of the float bowl but everything else seemed okay. Of course not knowing all the passages there could still be one plugged and I could not tell.

Oh and Chris, the chances of me figuring out how to do a video of it idling is almost as good as me getting it to idle properly!

Michael

Your engine may be running too lean. A lean mixture ignites sporadically and may cause the problems you describe - a lean misfire.

A common cause is an air leak somewhere - manifold, gaskets, worn throttle spindle etc. The usual method of diagnosis is to start the engine and spray the carby & manifold externally with something like WD40. It will temporarily block any air leak and the car will momentarily run properly. Give it a go - you've got little to lose

Chris

Hi Michael,
Interesting- the 'hole' in the side of the insulator block should have a thin metal tube protruding out of it with a small bleed hole. If the tube is missing you will end up with a large air leak in the 'manifold' and it will be impossible to get a good idle.
Here is a link showing what it should look like: http://webshop.fiat500126.com/katalog/artikelinfo/415/bakelite_piece_base_for_carburetor
If the tube is missing the best option would be to replace the insulator block but if you can achieve a good idle by blocking the hole it shouldn't cause any serious consequences.
Sounds like you are on the right track now!
Regards
Damon

Well ain't that just the cat's meow! That would be nice as I think we have done everything else except pull the engine. Now it's to figure out how to get a new one or simulate the missing one as it is indeed missing. Thanks guys for all the help. I will let you know but I am pretty sure we are onto it now.

Okay guys, the idle is good. I made a pipe out of Sterling Silver (why? because I had it laying around, I dabble in Silversmithing) squashed the end so there was but a little hole and voila as they say, smooth idle at around 850 rpm. (I will post a photo later)

New problem . . . Now when driving and the car has warmed up really well the engine seems to cut out (almost like I would turn off the key for 1/2 a second then turn it back on) I suspect the coil but am unsure. Any guesses out there? Also the car seems to run extremely hot, though this may be typical for this air cooled car, I was just wondering how hot is too hot?

Michael

Good news Michael.

Could well be the coil causing the issue, certainly sounds like it maybe breaking down when hot which I have seen before. Seeing as you are running a 123 distributor I would recommend upgrading the coil to a high energy one like a Bosch Blue it will provide a much better spark, I think it is recommended with 123 to upgrade the coil. I am running my standard setup with a Bosch Blue coil.

In the UK I picked a new one off Ebay for about £25. The part number you want is 221 119 027.

The engine does run quite hot it is the nature of the beast, I would just check that the thermostat valve is opening the flap on the side of the engine housing below the distributor ok. If left idling I would expect it to be fully open after about 10 minutes or so, obviously dependent on the outside temperature.

Tony

Given that there is so little information available about the IMB carburettor, I thought that I would gather what information there is plus a whole lot of photos of mine as I strip it down and post it in a new thread. Any thoughts?
Chris

PS: FWIW, I agree with the above about the coil.

Bambino said:

Given that there is so little information available about the IMB carburettor, I thought that I would gather what information there is plus a whole lot of photos of mine as I strip it down and post it in a new thread. Any thoughts?
Chris

PS: FWIW, I agree with the above about the coil.

Click to expand...

Good idea Chris on the carburettor thread. I am sure it will prove to be invaluable to all.

I agree! Great idea Chis.

As to my problem that little tube that was missing caused me a lot of grief! I am on the search now for a new coil I guess.

Michael

I attached a photo of the pipe that I made for the bakelite base.

Hi Michael,

Very nice work, how are you with jewelry

I've attached a couple of photos of my original broken bakelite insulator (left) and one from a later model Fiat 126 on the right that used the bigger 28IMB carburettor.

The original does not have the fuel drainage channel nor the associated drain hole that gave you so much grief. I guess the fuel just leaked out on to the (broken) bakelite tray and dripped through the hole or evaporated off in the heat of the engine bay. Probably not particularly safe.

Very early on I ditched the IMB and installed a better carby, so I've not experienced the leaning out issues that you described.

Glad you got it all sorted.

Chris

Do you know the function of this tube? is there a specific size hole, material, length? Is there a reason for me to go out looking for a new bakelite bit or do you think my 'tube' will do.

Michael

Oh, and as to jewelry I am purely an amateur (as I am in many other things) though my Wife is happy with her jewelry box!

Hey Tony,

Do you think that coil (Bosch 221 119 027) would be a suitable replacement for the original in my Wife's car or should I be looking for a specific model to go with the 123 ignition?

Michael

CsFiat said:

Hey Tony,

Do you think that coil (Bosch 221 119 027) would be a suitable replacement for the original in my Wife's car or should I be looking for a specific model to go with the 123 ignition?

Michael

Click to expand...

I had a look on the 123 website Michael and they only mention a problem with using high power coils on the unit they produce for 2CV's. They don't mention anything else about 2 cylinder cars. But there is a quote on there

"On all other 4 & 6 cylinder cars: if you use anything else then the original coil make sure its primary resistance is NOT lower than 1.5 Ohm. We have good experience with "Bosch Blue coil", "Bosch Red coil", "Beru ZS 106" and "Beru ZS 109".

The Bosch Blue is 3.5 Ohm so should be ok.

I also found this on a website in Holland, right down the bottom they recommend the Bosch Blue with 123.

http://www.leenapk.nl/FIAT2R.html?category_id=69

Tony

CsFiat said:

Do you know the function of this tube? is there a specific size hole, material, length? Is there a reason for me to go out looking for a new bakelite bit or do you think my 'tube' will do.

Click to expand...

Hi Michael,

As far as I can see, the tube is to drain excess fuel from the groove at the base of the carby. Fuel may accumulate there from either the mixture screw or choke (starting) apparatus. I've attached a not very good photo of the underside of a 28IMB showing where this may happen.

The tube needs to be long enough with a small enough hole to prevent retrograde flow of air yet allow fuel to drip out. Yours looks fine and having been made of sterling silver is probably worth more than the rest of the car Only kidding. Reminds me of all of those Lada jokes - how do you double the value of your Lada? Fill the fuel tank etc. etc.

Chris

Yep, saw those when I was cleaning the carb. Great! One fewer items to acquire. I just ordered the coil so hopefully that will cure my other problem and Christine will be on her merry way. I am hoping to do a little bodywork this winter and perhaps a paint job next spring. (as long as nothing else breaks/needs fixin') Using Sterling Silver for any other repairs could be costly!

Okay Tony, the blue Bosch coil is in. It has numerous connectors on it but I imagine it connects up the same way as the old one right. I just pay attention to the positive terminal and the rest falls into place, right? If so then I will let you know how it works out after I hook it up.

Michael

Yes that's correct Michael just connect as per the old one.
Tony

Now if social obligations can get out of my way I will get to play again and see if that cures the problem. Maybe tomorrow? Not sure, will have to check with my Social Advisor! :O)