What would cause a car not to start after changing the alternate?

Im unsure on how i can check if the injectors are working. I would have to take off the intake manifold just to get to them.

I called the owner than they confirmed it did not have a alarm system.

Remove the spark plugs and check if wet. If not using a syringe add 5mm of fuel into each cylinder, replace plugs and try. If it fires up and stops immediately then check fuel pump. By the way have you checked the spark plugs?

I have not been able to check the spark plugs due to the intake covering up 5 of the six plugs and the sixth has very bad threads. I did however spray starter fluid into the intake and got it to turn over, it ran for about 5 seconds than died again.

And there in lies the problem. Check fuel pressure. Change all fuel filters and make sure fuel tank breathe is not blocked. Start with the fuel pipe on the inlet manifold. Then filters.