Nismoleon

Im dealing with an issue on my 2004 350z. A week ago when coming home from work i noticed my oil pressure was at 120 at 3.5k RPM in 6th gear. I drove home as slow as possible and then i replaced the oil pressure sensor. Car ran fine i drove it around my block a couple times. Shut it off. The next morning for work i tried starting it. Car cranks but engine wont turn on. I replaced the battery because my voltage was at around 4 when I turned the key and put the window on passenger side down at the same time. After New battery install car still cranks but engine wont turn on. There is a battery icon on my dash but I dont know if thats just on until my engine starts because before I had this problem i never had a battery icon on my dash but the z would only start the second or third time I turned the key. If anyone has dealt with similar issues please help. This is my DD. Need it for work.

bealljk

iTrader: (13)

You’re oil pressure sensor would have no bearing on the engine starting or not - the sensor only sends a signal to the triple gauge oil pressure gauge.

The battery light on the dash indicates you have an issue with the charging system - such as your alternator has gone out. But you should be able to start the car with a fresh/fully charged battery with no alternator.

Soooo … lets start basic

do you have any check engine lights on?

Have you done any work on the car in the past few weeks?

Do you see any loose wires or anything unconnected?

Can you ensure you dont have any blown fuses

Lets assume that you have a full tank of gas and if you are anything below 1/2 tank or 3/4 tank maybe go get a gas can and put 5-7gallons in the car

When you insert the key and/or crank the car is the antitheft light solid or on?

now that we know you have fuel in the car, can you hear the fuel pump prime when you put the key in the ignition and turn to ‘key on’? You should hear a fuel pump / motor buzz for 3 seconds or so after you turn the key to the on position.

You need to determine next if you have fuel pressure - it’s probably safe to assume you do, so lets revisit this if nothing else works.

When was the last time you changed your spark plugs? If you dont know, it may be wise to replace them. Otherwise, pull a few spark plugs to ensure they are not fouled and are otherwise in good shape.

From here it gets a little trickier and if you dont have the right tools or experience you may just want to take the car to a mechanic so you’re not throwing parts at it. But if you’re inclined

You’d want to make sure you have fuel pressure - Stock is 52psi but to get the car started you’d really only need 20psi or so

Youd want to make sure your cam shaft and crank shaft position sensors are in good shape and giving the ECU a good signal

let me know how this sounds and how many of these things you can get through

Aeneas137

just because your battery is new doesn't mean it has a full charge when your alternator is going out. If it drops below 12.0 v, it probably won't start the car. maybe, maybe not, but not likely in the 11s. disconnect the battery and put on a charger and when it gets up to high 12s, then disconnect the charger and see if it will start. probably the alternator though, right? on these older cars, everything you replace is just going to help it in the long run even if that's not the problem. I don't worry about replacing stuff that might be a wear and tear item. it's just going to go out eventually anyway.

Nismoleon

thank you for the in depth response. I actually did all the trouble shooting you mentioned and ended up being the crankshaft sensor. I replaced with OEM Hitachi CPS0006 and turned on just fine. I let the car warm up and took it for a drive this morning. Going to replace the camshaft sensors on Thursday. I went through the 5 stages of grief and almost sold my car.

Nismoleon

Thank you for the response. Alternator is running solid and the issue was the crankshaft sensor. Going to be doing a lot of preventative maintenance in the next couple weeks. I don't want my Z to ever have problems again haha

Aeneas137

That's good, glad you got it sorted out. these are robust cars so they keep on going until a part completely fails. I also came to that point you're at about replacing things. a lot of rubber wears out after 15 years.