Engine starting problems

[stephen290361]

Hi All

I have a 1961 MK9 Automatic that I have restoring for the past 5 years. The engine has been totaly re-builts and the carbs re-furbished when I start it up the engine will run at around 1500rpm for about 10 second and then it will just die. The only way I can get the car to keep running is to rev it up to about 3500rpm once it is warm she runs fine. The autochoke is working and aux carb has been re-built.

I was not sure where to post this as there is no dedicated MK9 site but a 3.8xk engine is the same in any car.

[DaveEssex]

Seems to me that this is a classic too rich/too weak mixture issue. From your description, if you are absolutely sure that the auto-choke is operating totally correctly, ie is only cutting out once the temperature sensor in the inlet manifold switches it off, which from cold will normally take much more than 10 secs, then I suspect that the carbs are set at too weak a mixture.
I should say here that it is important to be sure of your diagnosis, because the reverse, too rich a mixture will anyway always result in normal hot and cold start-up problems.
I have previously invested £10 approx in a book titled "SU Carbretters Tuning and Tips with Techniques" - (sales@ brooklands-books.com) or listed on Ebay currently. search "SU Carb".
Hope this is informative.