Car wont start, cant figure what is the problem

[s13drft89]

Alright its a 91 300zx N/A, well the car started misfiring so I pulled into my garage found out the #2 injector was out .01ohms, i went ahead and changed it in 20 minutes with a new injector from work. As i start it, i still noticed it had a misfire, so i get out of the car and walk up to the front of the engine bay car just dies out, out of no where. Go back in and try to start it all it does is crank spins freely(motor isnt locked up), i checked for fuel gets fuel, checked with my noid light for injector pulse all 6 are good, good on fuel pressure form the pump, one thing i cant figure out is for spark, now i doubt all 6 coils went out at once, if at the most if i was "lucky" two would have gone out. Only thing i havent dont is check for codes from the ECU. What iam thinking is the CAS? how could I check it if I even can. Iam out of ideas, even though iam doing a motor swap soon, just would like to drive it for the last week or so. -Ricky

[Duce40sx]

First off,

You're lucking the crank spins. Mine's locked.

1. Air 2. Fuel3. Ignition

a. Did you mess with the timing? I'd do a timing job.b. Check spark, shoot the coil at a groundc. Do you hear the Fuel pressuring up?d. CLEAN out the Injector Connectors, If it's Green then needs to be CLEANED.

[Milo (San Antonio)]

I'd check the CAS with a known working one, like you are thinking. You said fuel pressure is good so that rules out the fuel pump. You checked all injectors, so that rules fuel delivery out.

For spark, check the PTU and check the plugs as well. Also, check to make sure you didn't foul up the plugs as well.

Other than a starter relay, that is all I got off the top of my head.

[Canyoncarver]

Only thing i havent dont is check for codes from the ECU.

Why don't you start there?

[Duce40sx]

What ever you do, don't get angry and take out the whole engine like I did.

Just Do an ECU diagnostic and reset it.

I say check for spark and Fuel.

Do a timing.

[s13drft89]

Right after i posted i went out and checked the codes for the heck of it pulled up 11 and 21. So of course 11 is the CAS, i went ahead and searched online and found out a way by 300zx.org.uk on how to check the CAS. All injectors pulsed, fuel is coming i did a compression check for the heck of it and got 170-175 range through all 6 cylinders. Only thing left is spark, went out and changed the rely for ignition and egi checked the others turned out fine. Plugs aren't fouled. Man iam stumped. Oh yea never messed with timing all that was changed/touched was a injector which iam changed plenty, i went out trying to see any "clips" that might be unplugged, nothing. Only thing i have a question about is the "PTU" what does it do? i came up empty handed on trying to figure out what it does. If anyone has any other ideas please shoot them towards me. -Ricky

[Canyoncarver]

Next thing to do would be to clean all of your electrical connections. Mainly the CAS, PTU, & coil pack connectors. These cars are notorious for connector corrosion causing problems. But, you can start replacing good parts if you like also.

[Zwicked]

I would first off check the connectors on the PTU (and all others) as corrosion is a huge reason why the VG engine sometimes has issues.If it doesn't start, once that's done, pull a coil pack, insert spark plug, ground it and turn the engine over to confirm if you get spark. If you don't get spark, the PTU could be toast.Also:Have you checked your ground wires, specifically the one that are at the back/top of the plenum and the bolts that hold the PTU down? Poor/intermitant grounds can cause it to burn out.