Someone told me that there is a sensor on the engine where the fuel lines go in, iam wondering what sensor this is??? Please help.

 

Well, I'm assuming you are talking about a '96 Blazer, but since I can only go by your only other post here, I could be wrong. Please include your vehicle information in your signature and attach it to your posts.

On a '96 SCFI 4.3L, in the fuel system, you have the Tank, the screen, the pump, the filter, then the lines run up and into the injection spyder where it is metered out through 6 individual injectors that are centrally located in the injector pack, through 6 individual tubes, to poppet nozzles before it is sprayed into the intake runner... Fuel pressure is maintained with a fuel pressure regulator off the back of the injector pack.

No sensors... Don't know what you friend was talking about.