Poor cold start - solved!

[DetomasoLee]

My new two me 240z, very original car, runs nice but is (was) a poor starter when cold.
I watched a few videos on the SUs and went to investigate.

Basically even though I was pulling on the choke level and it appeared to be moving the external mechanism on the carb it turned out the variable mixture jet was completely stuck on one carb and sticky on another resulting in 1) the jet not actually returning to the top of the bridge (so impossible to set the mixture properly) and 2) the jet not being pulled down enough to richen the mixture.

A bit of manual movement and carb cleaner got them both to move much more easily and from a dead cold start with the choke level pulled and confirmation of the carb levers and jets in the correct on-choke position it fired on the first revolution!! so, very pleased with that. Now I'll pull them and clean them properly.

 

[Rob Gaskin]

Well done. Time spent on checking and adjusting carbs is time we'll spent.

 

[uk66fastback]

Both of mine were completely gummed up and basically inoperable when I bought my car. I’m guessing the fact it came from a warm state meant it never really ever had to work …

 

[AliK]

Well done for solving it.

I find a squirt of WD40 around the jets once in a while (once a year even) keeps them from going sticky. But then again, my domes are off and on regularly with my carb tuning OCD so it’s easy to do. Sticking jets can cause so many headaches!

Be sure to visit the Burlen website and buy some official SU damper oil as well to keep the dash pots topped up.

 

[DetomasoLee]

Thanks, yes I removed the nozzles and found a green coating on the, which I could tell was causing the sticking. A bit of googling showed that others had removed this coating. So I rubbed it off with some fine scotch pad and then polished them a little. Nice and smooth now up and down

 

[toopy]

Thanks, yes I removed the nozzles and found a green coating on the, which I could tell was causing the sticking. A bit of googling showed that others had removed this coating. So I rubbed it off with some fine scotch pad and then polished them a little. Nice and smooth now up and down

That green coating is on them from new, I assume as a sort of interference seal of some kind, if the jet bearing is also new they can be a 'bit sticky' together, but often a little careful rub with very fine wet & dry paper cures the problem.