I have a G35 v36 2008 (mileage 90k km) sedan and I got a problem.
Sometimes car won't start, it cranks but engine is not starting. Usually it takes about 5-6 tries to start the engine (one time it only started after a couple of days). It does not depend if it is a cold or a warm start. Additionally, sometimes car stalls, it may happen right after starting the engine, or even when I'm driving it. The problem appears absolutely randomly, I can be driving or starting engine without a problem for weeks.
In service I've been told, that it is a bad fuel pump, so I've switched fuel pump with a new one, but it did not solve the problem.
Battery should be Ok, I got it changed around year ago.
Can someone help and tell me what I should be looking at to solve this?
---edit---
It also did not have any error codes, and check engine light is off.

 

Check your cam/crank sensors it's probably one of those. You can test the resistance of them and it can cause similar issue, but I would try to diagnose it first. Just had to replace my cam sensor too it did throw a code. But, it was hard to start, have to start the car in clear flood mode.

 

Definitely sounds like a cam or crank sensor, when it won't start pay attention to the tachometer, if the tach doesn't move when cranking it's the crank sensor. You can also carry an OBD2 scanner with you and usually pull a code when it stalls or won't start. It will also store the code until it self-clears and it will not throw the SES light on for intermittent failures like that. It throws the SES light when it no longer sees the sensor at all.