Been awhile since I've posted, I've recently finished rebuilding my 1984 300zx Turbo and I've run into a bit of an issue here...I primed the motor fully, oil is at the top and lubricating everything, it has spark, oil pressure and fuel pressure but it won't start. It's trying REALLY hard to but just can't seem to do it, I do have a seal missing on the down pipe that connects the turbo to the throttle and I did manage to get it rotating on it's own for about two seconds and then it quit, I'm thinking that's what it may be, but I'm not entirely sure, also the knock sensor is completely gone, but I've been told by numerous people that has nothing to do with a no start situation. Any ideas as to what to check here? Also I noticed there is a way of messing with the distributor, as in turning it and adjusting it via a screw that holds it down to the engine head, could this have anything to do with it?

 

Engines need 3 things to start:
-Proper air delivery
-Proper fuel delivery
-Proper spark delivery

A seal? Or coupler? Pics? A gaping hole in the air intake would definitely cause starting / running problems.

Yep... that's called "adjusting the timing".

I suggest checking out the FSM: XenonZ31 Reference

 

when you say down pipe are you talking about the air delivery tubing from the turbo to the throttle body. down pipe generally reserved for exhaust to turbo piping. if you have a big air leak as nismo said she won't act right. if you didn't install the oil pump correctly the ignition timing is off. look at the rotor when the engine is at TDC on #1 cyl and see where it is pointing.


When trying to start without success you can easily inject enough unburned fuel to effectively flood the engine (using old carburetor terminology). this then prevents you from starting the engine normally. If you have checked everything and still no luck try this. disconnect a wire from the fuel pump so it won't pump (on a z31 pull the fuse). you need a fully charged good battery for this. hold the gas pedal to the floor and give it a long crank. you may or may not get a few pops. Do it again. it may run for a few seconds. do it again. When you no longer get any action reactivate the fuel pump and try a normal start.

 

Where should the distributor be positioned for it to run best? and as far as that hole, it's the rubber seal that holds the pipe leading from the throttle to the top of the turbo, that may have something to do it with. It's definitely trying to start, I'll try the fuel pump trick and see if I can mess with the timing on the distributor too.

 

with the engine at TDC on the compression stroke for #1 cyl the dizzy rotor should point at the plug wire going to #1 cylinder. remember there are two count em two TDC position for each cyl. four stroke cycle engine. suck squeeze bang blow. check you wires for correct rotation it is in the manual. you can play with the dizzy all you want but it has to be in the correct position and the wires have to go to the correct cylinders in the proper rotational order. the screw only allows for maybe 30 degrees change in spark.

if the tube you are talking about goes to the waste gate actuator you may have real problems if you do get it running.

 

I had a similar issue with a friends Toyota Rav4, it had spark and fuel but it wouldn't start...Took it to a shop and it turns out it was the crank position sensor. I'm pretty sure that's what it is here too, I did set the distributor in the right position and the spark is healthy so I'll try swapping those sensors out and see what we get, my friend seems to think it's the intake pipe leading from the MAF to the turbo and up to the throttle body, not being sealed properly and causing the computer not to register the correct amount of air going in. It could be, so I'll try that too.