Very hard to start, stalling at the lights, fine when hot!!

I have included a YouTube link at the bottom of this topic.

I'm having trouble starting my car and the problem is deteriorating.
I have a 1.3 driver MK1 running a Weber 32/34 DMTL carb, and I took it to a rolling road where the specialist cleaned the carb, replaced the jets, altered mixture etc.
It ran pretty well after that.

It sounds as if it's running too rich but then won't start or idle until I apply lots of throttle. Choke doesn't do much. It bogs right down unless its above 2000 RPM after starting.
The carburettor often backfires into the air box when I am starting the car, and also when I use engine braking going down a hill, and I'm not applying throttle.

What is peculiar to me is that once the engine is hot enough, the car runs fine. If I leave my car, even for a good few hours, when I come back to it after driving it that day it starts on the button and idles perfectly. The problem basically only appears after leaving it overnight.

After researching the problem, we fitted a non return valve on the fuel line, and replaced the fuel filter. We have also adjusted and reset the idle, to see if this helped, but no. Given the carb was serviced not long ago, and has a new air-box on it,
we are a bit stuck!!
If anyone has a suggestion, or has solved a similar issue, please get in touch!!


A YouTube link to the starting process of my car:
https://youtube.com/shorts/a8GMRShFwgQ?si=kxJegVaRkCST4pe8

 

Hi,
I am running a 1.3 too.

Are you running the correct jets inside that webber for a 1.3 engine? Have you checked which ones are in there?
It sounds like an air leak/or blocked jets, or base gasket is broken or not tight? and air is creeping in.Spitting back suggests air getting in or a very weak mixture. Is there a fracture on the pipes to carb or air box?Joints and pipes change when hot or cold. Engine breaking down hill would produce a vacuum so sucking in through any leaks.

but it might be the old problem of the fuel pipe getting blocked by debris in the fuel tank. (I had endless problems with this that I thought was carburettor or lift pump}. Have you tried removing the fuel cap, then blowing back into the tank -not with airline- as could blow pipe off tank outlet. any real resistance is a partial blockage! and if you blow hard enough it should suddenly clear and the solution is to fit an inline plastic fuel filter on the end of the outlet pipe that drops in the tank after using a magnet to get out any swaff. is the tank clean? This filter will reduce the tank capacity to suck the tank dry but at least it wont partially block and the engine gets the fuel it WANTS.

I suspect the carb was not put back together 'correctly' after the rolling road (how much power did it make?60?) if mount is good Iwould take carb off, dismantle the jets out, make sure they haven't any dirt AND are the correct ones, then reassemble and try again.

Marcus.
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