Okay so I recently bought an 86 n/a that needed new head gaskets. I changed them (the heads weren't warped and were completely straight), and now I can barely get it to fire, let alone stay running. I got a new alt because the one that was on it was dead. Originally I also plugged the fuel pressure regulator wire into the distributor, and the distributor wire to the fuel pressure regulator, would that be giving me this problem? I know it's getting spark because I just bought new plugs for it too. I'm all out of ideas and this is my first Z car, so I was hoping you guys could help me. Any help is appreciated, thank you!

 

A lot to think about here. Somebody will ask you to be more specific about what the car was and wasn't doing when you got it - and what it is and isn't doing now. Clear pics of your current wiring and vacuum hookups will be good at some point. A list of what you have checked and measured and the results.

When a problem is specific, the Z31 guys here can pinpoint a fix because they have done it more than once.

When the prob is general or kinda vague, there are a lot of possible causes and many possible fixes. That makes more work for everybody. Maybe you can start with facts like mileage, location, any mods that were done, any non-OEM stuff on it, etc., etc.

Try to give enough info so you bring the car right here for everybody to check out. Just a suggestion. That car is worth your effort. People here are happy to help.

 

Okay well when I got it, it ran perfect other than it had bad head gaskets. Now it cranks but won't start most of the time, and if it does start it dies right away. When I changed the head gaskets I did an a/c delete and cruise delete. It's completely stock, other than it has an air filter now instead of an air box( that was how I got it). There is a vacuum line broken, I don't have a pic but it's one of the 4 that are right by the battery. I replaced the alternator also because the one in it was junk. It's the same exact alternator, only it was made for a Subaru, idk if that matters. I just put brand new spark plugs in it. I didn't replace the plug wires though (bit of a tight budget). The dash power supply in it is also bad, but I don't think that it wouldn't run because of gauges not working. That's it I'm pretty sure. I can get some pics later, the car is in the garage at my moms house so I can't get them now. Is that more helpful?

 

Any help would be greatly appreciated. If there is more you guys need to know too let me know. This is the only car I have right now and not having it is making it hard for me to get to work, so any help is appreciated

 

My guess is that you have a massive vacuum leak somewhere. You've actually made some pretty major changes to the basic vehicle, so I'm thinking you've introduced an unregulated source of air.

 

Yeah. Gotta do the vacuum lines right. You can work off of:

Vacuum Lines

I've done mine three times on two Z31s. Screwed up vacuum connections make the car go crazy or not at all. Best advice I can give you based on your symptoms, first find another 86na that is running right and pull up next to it, trace every vacuum line end-to-end in both cars, comparing yours with his. You maybe switched a couple of lines by mistake during that gasket work you did. When you are sure all of yours are right on both ends, replace them with new hose - one at a time. Use the right diameter.

 

Thanks a lot guys I'll check it out tomorrow. As far as pulling a running one up next to it, I'm the only guy I know of in my area that has a 300zx. Me and my buddies are pretty much the only ones into JDM and they have 240s. But my friend just pulled out his whole vacuum system in his 89 240 and it still runs fine. Obviously it's different lol but I just think it's weird. But I will check all the vacuum lines I can, is there a vacuum line diagram in the Haynes manual? I'm pretty sure if it is a vacuum line I know which one it hopefully is. Or where the cross happened at anyway

 

does the Sub ru -we used to call them that- have the same # of pins on the alt plug , wasn't of a carb model was it ?
do you hear a fuel pump running ?
just crimp or plug the interior vac lines and double check for a big leak

you did the head gasket job ?
checked compression ?
I would check & or move the distributor a tooth back
sounds as if it just barely fires

 

The alternator is exactly the same other than the plug is on the side rather than the back. Fuel pump turns on and runs(at least it sounds like it is, but it also sounds like it's turning on from the front, maybe that's the fuel pressure regulator?) I did do the gasket job (not the first I've done). It has compression and I tried the distributor, it's in perfect time. I haven't gotten a chance to get back to her yet, but I'm hoping I just connected a hose in the wrong spot. There was one I had no idea where it went

 

So it turns out it wouldn't run it start because when we were reassembling the engine we didn't bolt on the EGR valve. But now after it starts and runs for a little, there is this black tube that starts blowing air and it won't let my car idle. The tube looks like it goes down under the engine, somewhere beneath the no. 1 cylinder, anyone know what that is or what I'm talking about?

 

tube 1/4 or larger, not a vacuum line ? egr's vac line is on?

 

Egr vac line is on and where it's supposed to be, and the tube I'm talking about is like rectangular, I can get a pic of it if that helps. Although I'm not sure how to post a pic on here from my phone

 

No one knows what tube I'm talking about? It's right behind the power steering pump and goes down by the valve cover

 

Sounds like a few things- timing- if you set the timing belt wrong, youd know right away... Gotta love interference engines. The other thing is dizzy timing, make sure thats right.

The other thing it could be is an air leak. These engines seem to be very sensitive to air leaks/constrictions. My suggestion would be to eliminate as much of the vacuum system as possible (unless you live in cali), that way it cant be a problem, and unless the hoses have been replaced, they are probably rotted anyway. I think xenon has a good writeup of what to remove, its fairly straightforward.

 

The rectangular tube is an air duct to feed air up into the valley between the heads where the fuel injectors and feed lines reside. The way the intake manifold and plenum were designed to meet clearance issues, heat is trapped in this area especially when a hot engine is parked. Vapor lock can and does happen because of this heat build up, which is the main reason these cars can be hard to start w/ a hot engine. The duct should be connected to a small centrifugal fan run by a small electric motor behind the power steering pump. Many owners removed these because 1) they didn't know what purpose the fan served and 2) they didn't like the battery run down from the fan running when the car is parked. I'm not sure what good it does as I still get some vapor lock on hot days especially if I shut the car off parked on black asphalt. I suppose it could be worse without the fan.

 

That would make sense as to why it blows air out after a while and why my voltage goes down after a while too. As far as timing, the engine itself if timed correctly, the car does start and run now (although it needs to be jumped due to the battery in it being to small, I always used it as a back up for audio equipment in other vehicles) but I know the distributor needs to be tweaked because she likes to chug a little bit. As far as I can tell, I have the vac lines hooked up correctly but I've never found a close enough picture to actually be able to tell if they are all going to the right place. Also my digi dash doesn't work and I've seen that it is probably the power supply and I might be able to re solder the leads, but I have no idea what to soder. It's hard to tell if my car is running correctly when I have no gauges lol