Zenith carburetta problems

[Ivor Hawkins]

Ian, can you contact one of your local club members and borrow a carb to try, just to rule out any other spurious problems?

Have you tried starting the car and while it’s running spraying around the carb and inlet manifold with aerosol brake cleaner? A rise in revs will identify an air leak.

[Ian K]

Thanks I will attempt to clean the progression jet as you described. I am also not certain about the float level too
. I have changed the switch and played with the number of washers too but don't know whether I have sorted it.

[Ian K]

I cleaned the progression jet in situ as described but it made no difference and the engine still will not tick over without some choke. It also does n't have any power either unless the coke is outnumbered

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I cleaned the progression jet as described. It didn't make any difference and the engine continues to run properly and deliver power when the coke is partly out.

[Bob Culver]

I had that problem with my car years ago with old fuel. Would only run with some choke until refilled.

[Ian K]

I had a friend from my Austin seven club visit today with another zenith carburetta. We fitted it and the problem was solved. We then had a another look at my carburetta and found that one of the jets I had previously cleaned had become partially blocked again. We again cleaned all of the jets and now it works too. I had sorted the three jets in the float chamber but not the progression jet. When I eventually did, I didnt rechecked those I had already done. My mistake. Thanks for all the support. I am now going to fit a petrol filter unit into the fuel line. I think the source of the dirt was from my petrol pump which I have sorted.

[Bob Culver]

Harking back to the initial question, at low airflow and no choke applied the main and compensator jets do not contribute much. The slow run and progression jets do. I run a 1964 Minx; these cars are notorious for blocked idle jets, not entirely solved even with a filter. Apart from preventing idle (without jiggling the acceleartor pump) a slight faltering can be detected up to about 50 mph on the flat. It is avery hazardous condition. If the jet is dropped on the roadside have to walk home!

[Ivor Hawkins]

Ahaa! That’s great news Ian, it’s great to hear when a forum suggestion actually works out and identifies a problem!