I'm having an issue with my 350z lately where once the fuel is around a quarter full it will not start. I've checked the air filter and spark plugs and they were still good. I replaced the crankshaft position sensor and fuel regulator, the problem still persists. Once I fill the gas tank to full it's able to start after 1 or 2 tries and runs smoothly while I'm driving. I also plugged in a code reader and no errors came up. Could this be a problem with the fuel pump or could it be something else entirely? I've been struggling to figure out the problem.

 

Almost guaranteed to be an issue with the fuel pump assembly. One of the pump hoses could have popped off or could be damaged, causing a loss of pressure when that hose port is no longer submerged. Here's a pic from the FSM showing the internal tank/pump assembly hose I'm talking about.
Cheers!
-Icer


Pay attention to the images showing the removal of the hose on the side of the assembly.

 

On second thought, the issue could be as simple as an inaccurate fuel gauge. Perhaps one of the level senders is acting up (there are two level senders). Because of the gas tank shape, an average reading is taken from both. The main sender is part of the pump assembly while the 2nd sender is on the driver's side. If one of these fails, it could result in a bad gauge indication, which means you could be running out of gas without realizing it. When you fill up at the pump after this symptom occurs, how many gallons is the Z taking before the pump shuts off?
-Icer

How to check your senders are good with a multimeter.

The resistance values are given. If outside of spec, replace faulty level sender. (Note from a 2006 350Z FSM, but should be the same for all non-HR Zs).

 

This dude did all that talking just to hit that 10 minute mark for YouTube money. Lmao. Save yourself the time and skip to the end.




Tutuapp 9Apps

 

 

I agree that it could be something other than the fuel system or inaccurate gauge reading (such as NATS), but this statement from the OP is what led me to my recommendations. If NATS was the culprit, wouldn't the car fail to start regardless of fuel level?
Cheers,
-Icer