300zx not starting please help

[SCR34MGTR]

Hey guys i have a nissan 300zx i have just bought its a 1991 N/a Automatic, i bought it to make it a project car as it had no rego and when i tested it everything was fine (or so i thought, im a 2nd year apprentice mechanic so i checked everything i could think off) a few days after getting the car registered and actually driving it i decided to put my foot down to see what im dealing with, the car went hard and everything seemed fine, a few minutes later the car just shuts off, no idea what happened and i pulled over, turned the key started right back up, didnt think much off it then just thought a dirty fuel filter so i went and replaced the filter still happened again, this time it took a while longer to start, like 2-3 mins, after i changed that i tried the fuel pump, no luck had the same problem and now im stuck not knowing anything about these cars, i scanned the car and got 4 codes, the Cam angle sensor, Maf sensor, Coolant temp sensor and knock sensor, i changed the coolant temp sensor since it was the cheapest and still not working, now i know what your thinking change the Maf and Cas sensor, the problem now is the car doesnt start at all, and i want to be sure that what im doing is actually right, i checked the car and found a vacuum leak and fixed it, is this a common problem? how can i tell if its a Maf or Cas some people are even saying the ptu, i have never owned a car this old i really like the 300s and its just been a bad expirience so far i just wanna turn that around if anyone can give me any help at all or any ways to check what it is or fire the car up please post below and if anyone is selling any of these sensors let me know it means alot

[nissanfreak12]

Check all the connectors and see if there is what we call "green crud". If there is that will cause all sorts of issues. Especially if its in the MAF and CAS. Another thing to check is the PTU, do you have the old or new style? Is SIlver on top or black plastic looking?

Other things to check is:

Fuel Pressure, sometimes if the pressure regulator and damper start to go, sometimes that make it hard or no starts
How old is timing belt/how many miles?
Have you Ohm fuel injectors? Should be between 10-14 ohms

These are great cars but can be a b**** to work on. Just remember you bought this as a project. When is school, I think they forget to teach you how to properly diagnose problem cause OBDII which basically tells you what to do. OBDI is just a "hey, look in this direction, maybe." Also, cars, as you will find out, one minute things work and then the next it doesn't. Just keep on it, most of us have been there. Then once it is fixed, people will be amazed that you are able to work on what little room you have in the engine bay. It is very rewarding. BTW, we are all here to help and post some pictures.

[SCR34MGTR]

ill check the connectors when i get home from work today, i think its the old style its a 1991 and as for the black or silver i assume your talking about the lining around the targa tops and windscreen etc? its a black but it is peeling on my car and beneath is a silver, i changed the fuel pump and fuel filter to a walbro 255 there is pressure, the timing belt ive got no idea as these cars are so hard to work on i cant even get covers off from how cramped the bay is and also how do you check the fuel injector ohms? i dont go school its a bit different in australia the way i do my apprenticeship isnt like you guys, also ill post pictures later on tonight as i just bought the car and with all these problems wasnt really in the picture kind of mood but ill make sure to put some up thanks for your help

[nissanfreak12]

Ptu, it's on the left timing cover when looking at the engine. Driver side for you, I believe. If it is silver, it's the old style. Since you are in australia, I don't think you deal with the ethanol in the fuel there so less to worry about. In the states, the older style injectors were prone to failure due to the ethanol eating the coating away causing failure.

First thing I would do is read everything you need to know about the z32 on the main page. That will give you a better understanding of these cars. Yes, they are very tough to work on, most mechanics have no clue. They were ahead of their time. Start there, that should answer pretty much everything. Also, search is your friend. 90% of the time someone else has had the same issue.

[SCR34MGTR]

okay thanks alot ill be checking them now and checking the connecters for the green your talking about

[SCR34MGTR]

hey man thanks alot i took a few of the sensors off and done a few tests and when i spun the Cam angle sensor i heard the injectors fire so i tried to start the car and it started first go but theres a bit of a wierd thumping noise not a knock i assume since i moved the cas i just have to adjust the timing now, but do you think this is what was causing the car to stall as i was driving? also does this mean i need to change the CAS or could it have just been stuck or something?

[nissanfreak12]

If you did that, I am going to assume your injectors are either clogged or on their way out. Testing your injectors is actually very simple. Take the connectors off of the injectors. Be careful cause they are more than likely very brittle, you should see the head of the injector with two pins. Take a volt meter and set it to the ohm setting. take the leads from the tester to the pins, doesn't matter which goes onto which. It should test between 10-14 ohms, if it is any higher or lower than that, injector needs to be replaced. If there are any bad, it would benefit you to replace all of them with newer style injectors, less prone for failure.

Yes, taking off the CAS, you will need to retime the car. Make sure it is fully warmed up before setting timing.

[SCR34MGTR]

okay i will test the injectors but how do you retime the car do i just put a timing light and turn the cas until its on 15 BTDC

[SCR34MGTR]

i just retimed the car it was on 30 degrees BTDC .. im pretty sure that was it thanks so much for your help ill be driving it around and making sure it doesnt play up again and ill let you know how it goes