hi there, i have an old vw polo 1984 hatchback 1050cc with a weber conversion that i have had for many years now. 16 to be exact.
a year ago i had to have a new radiator fitted and had the head gasket repaired.since that time i have been plagued with carb icing in cold weather. i have replace the cold weather hose from the carb to rad and in my haynes manual noticed a cure for this as fit radiator blind (does anyone know what this entails?) prior to the new rad i had the problem but did have it sorted out, but unfortunately that mechanic who knew what he was doing retired and not many others know what on earth they are doing resulting in messing around with the carb jets, mixture etc causing more problems. apart from this winter problem my little old polo is fab and i dont really wish to swop it for anything else.
i would appreciate anyones input who has experience with this prob. my partner is very good with my car but he hasnt experienced this ever before and with the right info could poss cure it.
many thanks
julie
polo fanatic west london
Edited by Dynamic Dave on 27/11/2007 at 00:32
|
|
Do you still have the warm air feed to the air filter. ? When the head was done did they reconnect the heater 'Hedgehog' in the inlet manifold and reconnect the earth strap the carb and manifold. Regards Peter
|
|
The issue with carb icing is all about the air intake. If the car runs fine in non-icing conditions then there is no point in changing the set up of the carb. Make sure it's getting warmer air, however that should be done. The best solution might be to get onto one of the specialist owners' forums and ask for help/pictures there.
|
|
If this is the same as a slightly later Polo I had, there is a thermo switch mounted in the air cleaner housing. This switch operates a solenoid that either directs hot or cold air into the carb. On mine the thermo switch required changing - an easy and cheap job. The switch is connected via small bore vacuum piping to the soloenoid. You can prove that this is the problem by 'shorting' out the switch by re-connecting the vacuum pipes so the solenoid is driven directly. It will then be taking in warm air permanently. I think I have remembered this correctly!!
|
|
many thanks for your reply.been away and havent had chance to deal with this.but thanks for your info and i will check it.i changed the orange kidney shaped sensor previously but it didnt help.my partner is the carb genious so i will get him to check it out.
|
|
|
|
thanks for your reply peter.i havew been away so sorry havent been able to responmd.will check and see whats been done or not!
kind regards
julie vw polo
Edited by Dynamic Dave on 10/12/2007 at 19:26
|
|
whats the hedgehog? the rest makes much sense becaus all had been sorted until the radiator was changed.
|
|
|
|
|
I agree, the prob is due to lack of warmth in the air passing thru the carb, so in order to vaporise the fuel the carb is drawing in heat from the air around the carb body, thus cooling the carb body below the point where any water vapour in the air inside the carb will turn to ice. This is not going to be a problem on a warm day, but on a cold damp day it is. The size of the carb throat decreases due to the build up of ice inside the carb making it more and more difficult for the engine to get a sufficient volume of air/fuel, eventually it will stop running. As well as increasing the temp of the intake air you should also check that your air filter is not blocked because the harder it is for the carb to suck in the air the easier it will be for the mixture to get progressively richer and more and more heat will be extracted from the air around the carb to try and vaporise the fuel. So one quick fix next time it happens is to remove the air filter element, if it starts to run better that is your temporary cure.
Hope this helps.
|
many thanks.your comments make a lot of sense as i have had much vaccuming when this happens. i will get this checked.
kind regards
julie vw polo
|
|
|
|
when you converted from the pierburg carb, did you keep the standard airbox? I assume that you did.
If so then there are two systems that keep the throttle free of ice
1 - a small heater on the front of the carb. Sometimes this is not transferred over to the weber from the pierburg during a conversion. This is called the "throttle channel heater" (or somehting like that) in the Haynes. If the heater is there, check resistance to earth and check it gets 12v.
2 - the warm air flap in the intake, you've already replaced the air-temp sensor in the filter housing and I think you also replaced the warm air pipe. You should also check that the flap itself can move (suck on the vac pipe and see it move) and free up with WD40 if needed. you should also check that the line from the carb to the air-temp sensor is getting a decent vacuum, I think there is only one vac port on the weber
|
thanks for your reply, we had another icing episode on a4 yesterday. it happens when it starts to get hot after driving for about 15/20 mins. i will get your ideas checked out.we discovered that the inlet mainifold tap at top of car above everything else under black plastic cover had had tap turned off which wasnt creating adequate heating or air flow.its a real pain and flustrating as theres nothing else wrong with the car.
julie
|
|
What tap. The only tap under the cover is a blled screw for the cooling system as this is the highest part of the system. Regards Peter
|
|
|
|
