My mazda truck has a hard time starting, especially when its cold. As soon as you try starting, it seems too want too start instantly for a split second. When you jump start it, its ok or if you keep trying it will finally start but takes a while and a lot of starter and battery. It is fuel injected. I know its getting too much fuel but i dont know where to start. When it starts, it runs fine.

 

Sounds like an Engine Coolant Temp (ECT) sensor. This sensor reads the temp of the engine to determine the amount of fuel needed to start and run properly, rich or lean. Depending on the engine size is where it is located.