I have a 1990 300zx NA, and have done alot of work to this car. Had a JDM motor installed in the car about a year ago to give it a little refresh that was badly needed, along with some other stuff (headers, flywheel, clutch, alternator, power steering pump, heater hoses, radiator hoses, timing belt, pop charger, egr delete, etc.).
Anyways, the car started to run hot a little over a month ago, then a week ago it doesn't want to start, leaving me stranding at work. I finally got it to start by giving it some gas on start up, and it has been in the driveway since. So, I decided to upgrade the cooling system, and have just completed a couple days worth of buying and installing. Here's what I've recently replaced: radiator, swapped fan for electric (just to get some room), thermostat, water pump, and coolant temp sensor, coolant reservoir tank, and reservoir hose. As I was completing these repairs, I noticed a couple things. Reservoir hose was completely blocked with about 3 feet of rusty sh*t, and there was some rusty residue on the passenger side timing belt cover, PTU (which is a S1), and PTU connections.
After detaching and cleaning those and reassembling things, the car won't start. I've checked the battery(pass and charged at autozone), and the starter(pass at autozone), and cleaned the plugs, but haven't checked the ECU for codes(could i detach the ECU and just carry it to a mechanic for diagnosis?). So this is where the sages of z-driver come in... Could simply removing the Crank Pulley upset the timing? Could an apparant rusty coolant shower cause the S1 PTU to finally die, or am I over looking something? By the way I know i'm getting fuel(can smell it), but have yet to actually check for spark, guess I should do that...

 

If you have a series one PTU, it will die randomly, it doesn't need an excuse (that's why it was a huge recall item). Replace it... I can almost guarantee that if you seriously still have a first generation PTU, that's the problem.

 

Thanks ZLover, I've looked around for S2 P.T.U.'s, and most of the ones for sale seem to have a pigtail set with them. Is this for an SR/RB20 upgrade applications, or does the S2 just have totally different connections? (I'm hoping I wouldn't have to splice anything..)

 

The second generation has different connections and the harness is required to connect to the old harness as a result.

 

I bet he has the old style PTU.. Every JDM Z32 engine i've seen has had it (which is like 3...)

 

Does the engine still turn over just not start? Do you hear a clicking sound but no engine spin? Do you have an automatic or a standard? When you turn the key to the on position but before the engine starts can you hear the fuel pump turn on? What does the spark plug look like? Is it black and covered in soot? Is it grey and look burned? Is it normal? When is the last time you changed your air filters? Could they be blocked by a lot of dust/dirt? Did you check to see if your CAS is loose and perhaps got turned so the timing is all screwy now?

If it's an automatic you might have a bad sensor on the shifter or on the brake pedal (not sure as I have never owned an automatic Z) I am sure someone here has. If the engine turns over you can disregard this part.

 

Thanks for the help guys, Goofy, it's a J.D.M. manual trans., and the pop-charger was recharged about two weeks ago. My M.A.F. is clean, along with the spark plugs. The car turns over, just doesn't start, and I can smell the fuel when I have plug out to test for spark. I do have the brick look-a-like series 1 P.T.U., and can't get a replacement here quick enough. When I was last working on it I had to remove the C.A.S.'s connector, but am confident I didn't turn the sensor itself at all.

 

replace the PTU and harness, start there... Doesn't matter how quick you can get it, you gotta have it. NA and TT PTU's are the same IIRC.

 

Okay, so I got the Series 2 P.T.U. today, and installed it. Got the motor to actually turn over and run for maybe 3 seconds, then it died again, and would not restart. I let is sit for about 15 minutes, then tried it again. Nothing, same as before, it tries to start but can't get all the way. The first thing that came to mind is while I cleaned my plugs, they had just been through too much. So now a few questions: How sensitive are Iridium plugs (NGK) to wear like increased idle, not so perfect ignition timing, and excess fuel? What are the chances that taking the crank pulley off the car caused it to jump time? Can I remove the E.C.U. from the car and still have it checked for codes? Thanks in advance for any more advice or answers you can provide.

 

If the ECU is removed, it cannot be checked for codes - as a matter of fact, disconnecting the ECU is how to reset it. lol You can pull codes on your own, though, via self-diagnostic mode. http://www.ttzd.com/tech/diagnostic/diagnostic.html

The NGK plugs should be fine, I wouldn't worry about those unless it's running absurdly rich.

Get an ignition timing light and check timing... that'll tell you two things - if your ignition timing is correct (should be 15deg BTC), and also if your belt jumped a tooth (if the ignition timing is jumping around, it's because the timing belt is off time). However, I don't suspect your timing belt jumped a tooth... it's not common and it doesn't come with those symptoms (I installed mine off by a tooth without knowing it and was able to drive it for a day, wondering why it was performing like sh*t). If your car isn't starting, it doesn't suggest the belt has a problem.

When it was running, was it running smoothly or did it seem like some cylinders weren't firing?

 

It wasn't running normally, but since it was only for a couple of seconds, I couldn't really determine if all cylinders were firing. It just started up then stuttered and died. I just went out and followed the E.C.U. diagnostics. I got 21 over and over again, but having just replaced the P.T.U. (I got the unit and harness from Courtesy Parts.com, so they're new and should be fine) I hope it's not the front harness. That was the only code, (I'm thrilled at that at least), so just to be sure I was doing it right, I waited about 5 minutes, and tried again. The second time, I got 55, which is nothing, so I tried to start it, and it turned over once and then quit.

 

... the engine won't even turn over, now..??

 

Just tried it again... It will turn over now, but it won't start up. What I meant to say last time is when I tried it before, it actually cranked up but died again immediately after. What's really throwing me for a loop is that code 55.

 

Well the ECU diagnostic only tests the sensors.

I think you have a real mechanical (not electrical) problem with your car. Do a compression test and then test the fuel system (search for how to test the fuel system - I've detailed the process at least 3 times on these forums).

 

It really sounds like a fuel problem like Z lover said. Check fuel pressure, if you haven't replaced the fuel filter in a long time you might want to do that as a cheap shot in the semi-dark. The fuel pressure regulator and the dampener are more expensive and the pump is even more costly.

From what you described, i'd put my money on the fuel pump. Good luck.