Won't run after a boost
 

I have a 2002 Focus that is rarely used. It has a new battery and the alternater has few miles on it. The fuel supply was OK last time it was used. It runs for only a few seconds after it is boosted. I suspect it is something to do with the computer settings. Does anyone have a fix for this. Thanks..

There can be a fix for most problems,,,,,,bu first we need to determine just what is causing the problem.

A few checks might provide an answer to just which system is responsible. The laundry list can be long or short, but guessing can get expensive and disappointing.

In days of old, there were not too many possible causes, but with today's vehicles it takes a good understanding of just how the systems work and the equipment to chase down a problem.
From your description, it sounds simple, but we also learn not to go off the deep end until we have verified certain inputs and responses. Until we do that , we can only guess.

There have been problems with the plug that goes on to the alternator. You might look there for a poor fitting or loose connection. If the alternator can't do it's job of charging the battery, the only way to know for sure is to check and make sure it is working properly and this requires a meter and the knowledge of how to use it.

I will check that. Thanks Hanky