Technical UNO 999 CC stalls when hot

[vkr2007]

I have read almost all the posts similar to this in this forum, but could not find a final solution. Please forgive me if it is already answered.

My uno is a 999 CC FIRE engine with MIKUNI carburautor. ( It is in India. ) For some time now the car is stalling when it is temporarily stopped like at traffic lights or at junctions when I take my foot off the pedal. The mechanics checked the spark plugs, fuel/ air filters etc and report no problem with mechanical system, they advised checking of the electrical system by an expert.. When running on highways in the 4th or 5th gear there is no problem. When it runs in 3rd or 2nd gear for considerably long time this problem occurs. Often the car starts only after some time.

Recently I came across this suggestion from another post:
Something else for you to try next time you're in strife - hold the accelerator pedal all the way down (do not pump the pedal!) and keep cranking until the engine starts... release accelerator only when running... the extra airflow may help to clear the flooding and get you moving again

I tried this next time the car stalls, it works. The car starts instantly. Is this indicates a problem with the fuel pump / system ?. Where exactly shall I concentrate ?
Kindly advice me in detail, as there are very few mechanics with experience in uno cars here.
Thanks in advance

then wouldn't start again till it cooled down. The temperature of the day was not hot at all here in OZ, but I had been driving for about 45 minutes and got caught in some slow moving traffic. I have had the cooling system flushed after our previous hassles , but that was on an excessively hot day and the car has gone well until recently.
I have also noted that if I have been driving the car and then park and turn it off, if I go to start it again

 

[johorridoh]

A typical problem with a carburettor engine is that gas bubbles
build up in the fuel system when the cat is hot. That explains why the car starts up again after cooling down .
Maybe you can insulate the fuel pipes from heat or lead them away from hot parts. Maybe your fuel pump doesn´t build up enough pressure. High pressure prevents bubbles from building up.
Maybe the car get´s to hot at all.
So check the temperature also.
Are you sure it´s a carburettor , not an SPI ?
The SPI has a lot of problems with the potentiometer.
Can you post a picture ?

 

[vkr2007]

Thanks for the reply. It is a carburettor, not an SPI. Pic attached.

A typical problem with a carburettor engine is that gas bubbles
build up in the fuel system when the cat is hot. That explains why the car starts up again after cooling down .
Maybe you can insulate the fuel pipes from heat or lead them away from hot parts. Maybe your fuel pump doesn´t build up enough pressure. High pressure prevents bubbles from building up.
Maybe the car get´s to hot at all.
So check the temperature also.
Are you sure it´s a carburettor , not an SPI ?
The SPI has a lot of problems with the potentiometer.
Can you post a picture ?

 

[vkr2007]

Sorry for the small pic. here is a large pic

A typical problem with a carburettor engine is that gas bubbles
build up in the fuel system when the cat is hot. That explains why the car starts up again after cooling down .
Maybe you can insulate the fuel pipes from heat or lead them away from hot parts. Maybe your fuel pump doesn´t build up enough pressure. High pressure prevents bubbles from building up.
Maybe the car get´s to hot at all.
So check the temperature also.
Are you sure it´s a carburettor , not an SPI ?
The SPI has a lot of problems with the potentiometer.
Can you post a picture ?

 

[vkr2007]

Still no reply ....
Please help ....

 

[David Bliss]

I had two things happen on my Uno 45 (different carburettor). It was the opposite way round too yours, it liked to run hot and tended to stall when cold. It also had a flat spot, making it a bit difficult when driving in much traffic.

I eventually found two problems. First, the gasket between the carb and the manifold had swollen, blocking off the port from the air mixture screw. Secondly, the slow running mixture had weakened over the years and I had to make the slow running jet slightly larger. Before I found out what the problems were it was not possible to richen the idling mixture. At the MOT test it was shown to be running very weak.

Perhaps you have the opposite problem. Have you got an air mixture screw on your carburettor? Sometimes these screws have a blank cover to stop owners adjusting them. If you have got this screw try adjusting both in and out to see what happens. Another thing to look for is partially clogged ports (oily residue from the engine breather can block these over time).

I think the problem is more likely to be carburation than electrical.