Nissan Repair: 09 Nissan Hard Start, crank angle sensor, fuel pressure regulator

Question
I have a 2009 Nissan Sedan with about 45,000 miles on it.  About a month ago I jumped a friend's large SUV.  Immediately I started having problems starting the car.  When I first get in the car for the day (and even sometimes after I have been driving it then let it sit for a while) it has a hard start.  Sometimes it just takes a longer crank then it will turn over.  Other times it won't start after cranking for awhile and if I sit for a moment then try again it will start.  I've found that if I put my key in the ignition and turn it to on and let the car beep, the lights come on and the radio start then turn the key all the way it usually starts right up with no cranking.  What did I do to my poor car???

Answer
Hi, I doubt that the battery jump has anything to do with the problem you have. A hard cold start can be caused by the following reasons: 1 the battery voltage is low. 2 faulty fuel pump relay or fuel pump. When the ignition key is turned to the "on" position, the fuel pump relay activates the fuel pump for 2 seconds and then it stops. The reason for that, is to make sure that the fuel line has enough pressure that is required for the injectors. When you crank the engine the pump is activated again and builds the proper fuel pressure which is regulated by a fuel pressure regulator. 3 faulty cold start injector or leaking injector. And 4 a faulty crank angle sensor. I understand that you cannot check these components by yourself and you will have to take the car to a tech. But one thing you can check is the battery. Make sure that the battery always retains 12.6 volts and the terminals are clean, tight and free of corrosion. If the battery is in bad condition and has a low voltage reading, (below 12.2volts), it may crank the motor but it will not start.