My Z keeps cranking but can't start
 

Profile: 2006 touring 350z 40k mi
Symptom :

In the past fews months, I have been having occasional problem with cranking my Z. The engine would just keep cranking but the engine won't start. The weird thing is that after I turn the key back to off position, pull it out, and repeat a few times, and the engine will finally start. At first this symptom happens once or twice in a week and it's happens more frequently.

I took it to Universal City Nissan and the technician there said the problem is with the transponder of my key. I found that hard to believe because I got the key in less than a year. Unfortunately, I have only a set of key and I don't have the spare to verify what he said.

If the problem is really with the key, then why is the symptom getting worse over time? (The signal of the transponder is getting weaker?)

Let me know what you guys think.

What is your reason for not believeing the tech?

Your first problem is taking it to Universal City Nissan.

I would say just spend the $150 or so for a new set of keys; at least you will have a backup that way.

I had starting problems that got worse over time... turned out to be the fuel pump.

+1 on the Universal City issue. Try making the trek out to Performance Nissan in Duarte. They have resolved a couple of oddly troubling issues for me, and depending on where you live in LA it is worth the 40 minute drive or so.

I dont see how a key would be "dead" in such a short time. Your either not getting fuel or spark, or both. You have to find out why. Fuel pump, crank sensor, etc. Its gonna be a lottery guess for anyone on here to figure out without more info.

I've had this problem about 3 times as well. My Z has a brand new battery in it so it cranks REALLY strong but it just keep cranking but would not turn over. I try and try and let it sit. Eventually after a few tries and cycles of rest, it will turn over.

Without the key working he won't get spark tho.... So its a possibility.. One thing to check is that Wen cranking look at the red security led on the top of the dash. If its solid its prolly a transponder issue. Under normal situations it should go out Wen ur cranking....

It does sound like an intermittent problem, did it no start for the tech at the dealer? If he couldn't get it to do it, then he is probably throwing a guess out and saying that it's the key. I'm leaning towards crank sensor; with a good scan tool you can watch RPM's while cranking the car. If the RPM's stay at 0 then you know you have a crank sensor issue. (Or cam issue possibly.)

It's either the fuel pump or battery.

I had the same issue, turned out to be the crank sensor, but it threw a code saying such...

I had this problem, and the code said the crank sensor, had it changed twice, and I still have the issue. Some days my car will start fine, but other days, it'll not start 1-2 times and it'll take me about 7-10 tries on average to get it started. It's throwing no other codes :(

If I was in your shoes having changed the crank sensor I would now change the cam sensor. Sometimes they can throw each other's codes. For some vehicles, Nissan even sells the cam and crank sensor together in a package. You did use and OEM crank sensor and not an aftermarket one right?

Go back to what I said.