If I leave the key turned a long time, it sounds like the cylinders start pumping but very slowly. The car almost turns on for a few seconds even if I stop cranking the key, but then it shuts down again.

It's an automatic 03 G35 Coupe.

EDIT: Well it turned on. I tried a different key seeing that might be an issue, but I don't think that was it and just coincidence. It still had the very slow cyclinder pumping (or what I think feels like it) for a good 10 seconds, causing some shaking in the car. Then it fully turn on, but I heard a lot of squeaking, which I fortunately couldn't get my camera up to record fast enough. After about 15 seconds of that engine on with squeaking. It finally revert to normal.

Any clues?

 

1st Test your battery!
How old is it?
Battery cables?
Connections?
How much fuel is in the tank?
Why would you think the key was an issue?
Instead of trying to make a recording use your mutimeter to measure the voltage drop across your battery when attempting to start the vehicle.
Possible weak/dead battery cell?

Telcoman

 

Start by adding 1 gallon of fresh premium gasoline to the tank, your combination meter might have failed and you could be completely empty.

That sounds like fuel or spark, the ECU is TRYING to start it because it almost catches so I would rule out cam/crank sensors. The engine sounds like it's rotating at the correct start speed so I suspect the battery is fine but test it anyways.

Check the spark plugs, remove them all, don't be surprised if you find some wet plugs just from the failing to actually start but look for excess wear on the electrode, also check the coil packs, physically inspect for blistering of the epoxy resin on the top or burning on the well shaft, look inside the shaft and see if the spring is corroded or if the whole spark plug well is full of oil (valve cover failure).

If the ignition system LOOKS good test for resistance on each coil pack with a digital multimeter, I think it's supposed to be 2-4 ohms resistance, not 100% sure but you'll know immediately if you have one coil pack that doesn't give the same reading as the rest.

Fuel pressure is a bit trickier to test since there is no relief valve from the factory, remove the gas cap, put your ear up to the hole while someone else turns the key from OFF to ON (not start) you should hear a faint "whirring" sound for 1 full second as the fuel pump primes the system, since the engine almost started but not quite I doubt it's a fuel pump issue though.

 

Fuel is over half a tank and the fact that it did start (three times now since then) makes me think the fuel meter isn't broken. Always with premium. I'm always watching my miles and know how much I can get on a tank. Also like you I'm not sure it's the fuel pump because I can hear the injection occur when I start driving, but Ill check all this other stuff.

In the mean time, I also noticed some pretty loud squeaking noises when letting the car run. It's most loud when I have the car in drive and holding the break, stops when accelerating. Might be unrelated? break pads/rotors? It even makes the noise while in park though too, just not as loud.

It's possible a bad battery. I don't drive it much and I changed it somewhat recently. Had the car for 4 years from the previous owner before I had to change the battery and it's only been about 18 months since then. But I'll check that too.

I tried a different key because I read some things on here about that being a possibility if it loses its magnetic something or other, didn't think it would work but try everything first right? Especially when it's easy and you are a noob =).

Here vids of that sound:
When it gets louder I move the phone outside closer to the wheel.
Here's that same area after car been running a bit, harder to here the noise but it's still there:

Doesn't sound very good.

 

Sounds like maybe lifter noise, maybe a little exhaust leak. A mechanic with a stethoscope will be able to diagnose it for you.

So did you get the vehicle running or something or was that a video from an earlier time? If it did start and is running NORMALLY then I would suspect an intermittent failure of one of the cam or crank phase sensors.

EDIT: check your oil in the morning and make sure the level is fine, don't check the oil shortly after turning off the engine it's almost impossible to get an accurate reading until it's settled and cold.

DOUBLE EDIT: If the key fails then the engine will not crank and the security light will be flashing (or solid... can't remember)

 

Oil was good, key didn't fail. Yeah I've actually been able to start it every time since then no problems. Weird. I gotta check the spark plugs yet.

Also I thought infinitis using chains? But when I checked my engine it looked like a regular old serp belt on the engine? Would really like to locate that squeaking noise. Didn't see any exhaust leak either.

 

All manufacturers use belts for the ACCESSORY pulleys, the chain you're talking about is the timing chain which is buried under the metal cover that is the front part of the engine, some manufacturers use a timing belt, some a timing chain. Typically performance applications that have zero clearance between valve and piston use a chain because it's more reliable and lasts longer. Serpentine belts will squeak if they're old or loose.

While the vehicle is running it might be worth paying for a diagnostic at your local Nissan dealership to try to find the problem before it leaves you stranded somewhere.

 

Ah got it, so they are different. Well as I said I an a complete noob yet, Trying to learn as much as I can as I go. So the squeaking noise is def the serp belt, but yeah I am going to take this car in, since posting it's started 80% of the time, but has not started an additional 3 times. T

These times are a bit different than in the video in the original post. There's no error lights, and nothing happens. No crank, no sputter, no nothing. Similar to a completely dead battery in terms of noise, except the lights and stuff turn on. Does that sound like it might be the cam sensor as you said? I checked the spark plugs and they were fine too, so it's the only thing I haven't checked myself.

 

If you hear squeeking it's probably the belt and the replaceable tensioner pulleys, common wear item and the pulleys only last about 100k miles. Super easy to replace both.

 

A battery that is too dead to adequately turn the engine and start the car usually has enough power to turn on the headlights (dimly), interior lights and radio. So if those are on, you could still have a dead battery. The sound in the first video seemed to me to sound like not enough fuel getting to the cylinders. I do not know why it was not getting gas and cleric670 could well be right. I would bring it in as he suggested. Good luck.