Decrapify Update: '90 Z32 NA, radiator blowout, won't start

[TellarHK]

Hi all, I'm posting about a 300ZX that my partner is working on, which he'd sold to his sister around a year ago. The car was in pretty poor shape and needed some pretty serious work to "decrapify" it, which was shared with the forum previously here. The poor car's been kicked around the block a few times by the previous owners, and unfortunately a bit more by the sister. Unfortunately my information is second hand at this point, but I'd like to hear any input or questions people have. It's been dead about a month now, and we're running pretty short on troubleshooting options.

About a month ago, she was driving it at highway speeds when suddenly the radiator blew and she lost power. After pulling it to the side of the road and getting it towed, it was discovered that the upper radiator seal had completely blown out. She then told us that the thermostat hadn't been working for a while, which gives us the impression that it simply overheated and went kablooey all over the place. Coolant sprayed everywhere inside the engine compartment, but it was dried up by the time we got the car.

The mechanic she took the car to seemed completely clueless, and was talking about several thousand dollars worth of work without actually saying what it would be for. So we brought it here to work on ourselves, and have been going over various steps bit by bit in order to try and fix the problems. We are under the impression that the car was started, briefly, at the mechanic's, but are not clear on that given a somewhat unreliably related story of the situation.

Here's where things stand.

Radiator replaced, brand new, filled.
CAS tests correctly, fires when cranked.
Cylinders 1 and 2's spark plugs have tested fine and show spark.
2 coil packs with signs of corrosion have been replaced.
PTU replaced and testing fine.
ECU is only reporting problems with the knock sensor, which has a bad harness.

One spark plug and coil pack were covered in oil, so we know there's some kind of problem under the valve covers. We can't get to these ourselves, but hope this isn't a sign of something that's stopping the car from starting.

The battery is at around 85% at last check, and connected to a 150 amp start booster when we try and fire it up.

There's no grinding on the starter, and it definitely chugs like it's trying to kick over but there's no sign of combustion sound at all. The plugs have been checked and are showing a light moisture from the presence of fuel.

This one's a beast, folks. And we're still trying to save it, but we're running out of things we can do. Any help or questions would be appreciated.

[Corvidae]

I'm the one actually working on the car. Here are a few additional notes:

* All injectors are right at 12 ohm.
* Thermostat has been replaced.
* When the car is turned on, I hear the fuel pump click on. Fuel pressure seems fine.
* Air filter / MAF have been cleaned.
* Car exhibits the same symptoms in N as in P. Won't even try to start on other settings (which is good)

This is a strange one, and I have no idea why it's not working. Any input you might have would be greatly appreciated.

[t.mcginley.jr]

Have you done a compression test yet? That might tell you a little more.

Also if you can remove all of the spark plugs and try turning the engine manually (breaker bar + socket on the crank bolt) to see if it spins freely? If not it could be hydrolocked

[Corvidae]

If it were hydrolocked, wouldn't the starter be unable to turn the engine? It's turning over, sparking, but just not actually _firing_.

I haven't done a compression test, but it was running fine just before the "coolant-splosion."

[t.mcginley.jr]

So if fuel pressure is good coming out of the filter (should be around 43psi when the pump primes), have you checked the fuel pressure regulator and fuel dampener yet?

This is what they look like: