carburation question

[ronb1967]

Hi all
i have a 1999 polish import fiat 126 a/c
there seems to be a carburation fault which i can't seem to cure, all carb gaskets ok
initially on cold start i have to give full choke or car wont fire up,(partial choke and car not interested in starting) but if car doesnt fire up within 4 seconds, the engine seems to flood. At present the mixture screw is fully turn'd in, because even if i unscrew it out slightly it makes the engine run rough as if its over fueling ( choke is fully off) now i wonder if its something to do with the electro magnetic solonoid (pictured ) that is effecting the mixture, because if i screw the solonoid clockwise or anti clockwise even be a fraction this also causes the engine to run rough(overfueling), now i know the solonoid it working because i have removed it and it does move the needle valve in and out of the jet when the power supply cable is removed/refitted, although when engine is running and i remove the solonoid supply there is no difference in engine running atall
Any one have any info on this solonoid (carb is standard fit on this model )

Thanks in advance and appologies for the long winded discription     

[fightingtorque]

Not familiar with the specification of these, but it sounds like an electronic carb setup to meet the emissions regs that were in place in 99 - was it a pukka import (i.e. did it supposedly meet EU specs for 99 model year).  Has it got a catalytic convertor and lambda sensor in the exhaust?

Electronic carbs are generally designed to be a rich running carb, to which the solenoid leans the mixture out on instruction from some simple electronics, often driven by the lambda sensor.  So if anything goes wrong it will run rich, although should still run.

To be honest, these things are not really a big improvement from an enviro point of view especially if they aren't working and therefore I think your best bet would probably be to find an earlier specification carburettor for it.


What standard do they test it to for MOT?  I just MOT'd my Alfa and it is a 2000 model.  Reuirement at idle was 0.5% CO.  With closed loop and catalyst it ran at 0.41%.  MY iBIS which has no catalyst but was running about lambda 1 (the carb wouldn't run like that) mAde 1.79%.  I don't think you will make 0.5% unless you have a catlayst in the exhaust and even then it might be a struggle.

[Da Londo]

I believe the solenoid is only there for fuel economy at idle, I'd check the float, or fit the older type carb as fightingtorque says.

[GTMaster]

My carb. ran perfectly (an older Weber 28IMB, not like yours) and at cold starting it would only start with the choke fully open (pulled up lever). That is normal. As mentioned check the float level and needle.

[DEYAN IYI]

http://www.pf126.ovh.org/podstrony/danetechniczne/6.htm

Also not familiar with the "modern" technologies, but here is something about it (well, in polish). The idle cut-off valve (#64 in the scheme), controlled by the module (#70) stops the fuel flow over 1700 +/-50 rpm opens it at 1400 +/- 50 rpm, when throttle closed (switch #72 on the lever).

CO 0.5% at idle Euro 1. Great! Classic models make 2-2.5%.

Nothing about catalyzer in the article, nor in the scheme Any idea!? Is there a lambda-sensor in 126 with cat or it's kind of simple system?

Regards!

[DEYAN IYI]

http://img818.imageshack.us/img818/5443/93587902.jpg

Hm, I "found the hot water" There is no lambda, but the driver must control manually the process, so when the choke is open, the lamp on the dashboard reminds him to close it, but there is also a silent alarm, that makes him curse and not forget.  

Catalitic exhaust with lambda nut (only to adjust the mixture with external lambda sensor):



Cut-off module:



PS - from here

[DEYAN IYI]

Hi, again! Today I had the pleasure to play a bit with an ELX carb. I found that there is no chance to adjust the carb (without changing jets) except the idle speed or only if you take out the white plastic cover labeled FIAT. (To adjust it properly you'll need CO meter).

ronb1967: if i screw the solenoid clockwise or anti clockwise even be a fraction this also causes the engine to run rough

The solenoid must be fully turned in, otherwise the fuel will run around the jet uncontrolled.

With the solenoid unplugged is hard to start the engine. Needs to pump the gas pedal. Can't hold idle without pumping.

I hope this info will help you somehow

PS- that ELX (year 2000) is running with no catalyzer. Simple EL muffler. On the last MOT the guy said that it's strange if there is any cat (documents say YES), cos the CO was too high, like in normal old car. EL also makes 2-2.5% like the classic ones.

[ronb1967]

Thank you all for your input, ive printed off the relevent pages and will get them translated
As i previously mentioned if i screw the solonoid valve in fully this causes the engine to run very rough and no amount of adjusting the mixture screw makes any differance to engine idle , also if i slightly unscrew the solonoid to make the engine run smooth then remove the solonoid feed wire it makes no differance to engine running (there is no obvious differance in the engine tone)the feed wire is good because ive checked it with a test light and the carb is earthed ok , ive checked all the obvious stuff like float, jets, carb base gaskets and vacuum hoses all ok, at the mo once hot engine does run sweet   

[lilgreencar]

Here's a relevant discussion regarding this solenoid:

http://fiat500club.org.uk/clubchat/viewtopic.php?f=1&t=6381&hilit=solenoid

As mentioned above, it is a fuel shut-off, designed to be controlled by the ignition switch. The electrical contact on this solenoid must be wired to a circuit that is hot when you turn the ignition key "on" and "off" when you turn the ignition key "off". It should stay screwed in all the way as there is no adjustment provided in the design.

Hope this helps!

[DEYAN IYI]

Note that there are 2 types of diagrams for carbs with solenoid. The first is the commented one on the 500's forum for late 650E models, FL and EL (powered through fuse #2 or own one). It's only controlled by the ignition switch. The other one is the described above ELX one, controlled by electronic block trough the throttle position switch when throttle closed.