[280zxDat]

Okay so, this is my first project car and first car that is older (83 datsun 280zx NA) I'm having a weird problem. The car starts and runs fine cold. Can drive it for hours with no problems. Can turn it off after its warm and then instantly turn it back on and it runs no problem. BUT if I turn it off and then come back out after 5-10 minute wait and try to turn it on then the car starts stuttering until the fuel light comes on and then it dies. If I wait long enough for it to cool down then it's turns over and runs perfectly with no problems. I'm not really to sure where to start looking. I read somewhere something about vapor lock which doesn't make sense to me cause it runs just fine without issues. Thought?

 

[bonfire79]

download the Factory service manual for the 83 from xenonzcar.com in the S130 section. Start troubleshooting there.
It's probably not vapor lock.... that is not a common issue that I see on these cars personally and none of mine have the injector rail fan. does yours still have the fan installed? it is supposed to cool the fuel line. it could be something else though, may or may not be fuel related. have you replaced any tune up components? fuel filter, spark plugs, etc.
does the fuel pump kick on and run for 5 seconds when you first start up? (before ignition)
CHTS (cylinder head temperature sensor) is also something you should check. failing, these can cause weird issues on the 280zx. it is located on the head, right side of the engine.
lastly, your ignition control box may be getting hot (overheating) and causing a no-start condition. I would start by going through the fuel and engine control section of the FSM.

Bon

 

[Dave M]

next time try opening the hood after shut down, then close before restarting, see if that makes any difference in hot restarts.

 

[kickstand80]

Check your cold start injector. You have 7 fuel injectors. The 7th is located just downstream of your throttle body. Follow the fuel lines to find it. It is controlled by your thermo-time switch. Your switch may be bad and you may be putting extra fuel into the engine causing a flooded condition. There is a short piece of rubber fuel line before the 7th injector that you can pinch off with a small vice grip. Dont squish it too much as you may rupture or cut the line and we don't want a fire!. You can also unplug the cold start injector but that wont guarantee that the cold start injector is closed and leaking.
Also you may have a leaking fuel injector (one of the regular 6) and causing a flooded condition. You can check this with a pressure gauge and watch for pressure leak down after you shut the engine off. This isn't a fool proof method thou because you could also have a bad check valve at the fuel pump that would cause your pressure to fall off. The only fool proof method would be to pull the fuel rail, turn on the key to put pressure into the fuel rail and see if any injectors are leaking. The rail can be a pain in the rear to pull. I would do this as a last resort.

 

[280zxDat]

I am at work right now and wont be able to take a look at the car until tomorrow but I will look at the rail fan first since I know that I do have one. I noticed that it ran when the car shut off for sure about 2 weeks ago but recently I have not been hearing it at all when I get out of the car. I just assumed it only came on in certain situations, but if it is supposed to turn on every time I turn the car off then I guess I will start there. And I just got the car in September I believe. I was told the spark plugs were replaced when they guy i bought it from got the car, but I have not pulled them and checked them out yet as I was just trying to get it to run consistently since I needed it to get to work, so far I haven't had any problems besides a few small leaks which is to be expected, and know this problem which doesnt actually affect me to much since its usually cooled down by the time I turn it over again. I just dont want this to turn into an even bigger problem

 

[280zxDat]

And before I forget, the first time this happened I noticed that this black fuel hose was drip leaking fuel, not to sure what its for, since it was dark, cold and raining so did not look to hard into anything. I tightened the copper looking clamp, but have not re-checked to see if it is still leaking or not. IT has been raining alot, tomorrow will be first first day I can look at it again in the actual sunlight.

 

[mailnome]

If that is the cold start valve it shouldn’t matter for hot start unless the car thinks it’s cold.

It sounds more like vapor lock”. Seems reasonable for the timeframe after shutoff, but I’m curious whether it’s running hot, or hotter than normal, for some other reason.


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[280zxDat]

I wonder if it is “vapor lock”. Seems reasonable for the timeframe after shutoff, but I’m curious whether it’s running hot, or hotter than normal, for some other reason.


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The car warms up to temperature, gets a little warm until Thermostat opens and then the temperature needle stays right in the middle of the Gauge and doesn't move from there afterwards if we are talking about engine temperature

 

[mailnome]

It just sounds like vapor lock from your first post. It not actually locking up. The fuel rail just sits there absorbing the heat that the aluminum head and the the cast iron exhaust manifold are kicking out making the fuel in the rail very hot while it’s sitting. While it’s running the fuel has a constant flow through the rail and also through the pressure regulator that helps it stay cool.


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[mailnome]

It just sounds like vapor lock from your first post.


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That is if it runs fine the rest of the time. Though I rarely had it with my 79 ZX, I did occasionally experience it during the summer in the Maryland area.


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[kickstand80]

Your injector hair dryer blower is set to turn on for 17 minutes if the sensor hits 216° after the ignition is turned off.

 

[kickstand80]

And before I forget, the first time this happened I noticed that this black fuel hose was drip leaking fuel, not to sure what its for, since it was dark, cold and raining so did not look to hard into anything. I tightened the copper looking clamp, but have not re-checked to see if it is still leaking or not. IT has been raining alot, tomorrow will be first first day I can look at it again in the actual sunlight.
View attachment 112058

Yes that is your cold start injector (7th injector)

 

[bonfire79]

Being that we are entering winter (depending where you are) the fuel getting hot may not be your problem. Just a possibility.
as kickstand pointed out^^^^^^ the injector fan turns on only if it reaches a certain temp, and as Mailnome said^^^^^^^ you can open the hood after shut down which can help allow things to cool before the next start. but if it was dead summer and you were in Phoenix or Vegas, I could see this happening more often. Perhaps the injector fan is not working like it should and not turning on after shutdown?

I suppose you could try a test. Take the car out and drive it around for while, long enough for it to get hot and then shut her down. Wait and listen to see if the injector fan starts operating. You'll hear it. If it runs as designed for the 17 minutes and then after that, the engine still doesn't want to start, you may have another fuel issue.
If fan doesn't turn on and the fuel is hot, then that could be your issue, the fan itself. Again, it has to be hot enough in there for the fan to turn on according to the book.

I suggest going through the engine and fuel control section in the FSM and start from there. In the troubleshooting section, there is a diagnostic procedure when dealing with engine stalls, no-starts, hot-starts, and fuel delivery issues.

one other thing.... does it or has it ever shut down on you during mid-drive and then not start up again?

Bon

 

[280zxDat]

Being that we are entering winter (depending where you are) the fuel getting hot may not be your problem. Just a possibility.
as kickstand pointed out^^^^^^ the injector fan turns on only if it reaches a certain temp, and as Mailnome said^^^^^^^ you can open the hood after shut down which can help allow things to cool before the next start. but if it was dead summer and you were in Phoenix or Vegas, I could see this happening more often. Perhaps the injector fan is not working like it should and not turning on after shutdown?

I suppose you could try a test. Take the car out and drive it around for while, long enough for it to get hot and then shut her down. Wait and listen to see if the injector fan starts operating. You'll hear it. If it runs as designed for the 17 minutes and then after that, the engine still doesn't want to start, you may have another fuel issue.
If fan doesn't turn on and the fuel is hot, then that could be your issue, the fan itself. Again, it has to be hot enough in there for the fan to turn on according to the book.

I suggest going through the engine and fuel control section in the FSM and start from there. In the troubleshooting section, there is a diagnostic procedure when dealing with engine stalls, no-starts, hot-starts, and fuel delivery issues.

one other thing.... does it or has it ever shut down on you during mid-drive and then not start up again?

Bon

No, has never shut off on me while driving and it drives perfectly fine, my temperature needle while driving stays in the middle, I am actually daily driving it right now as my truck is messed up, so I drive it 45+ minutes to work and back home from work with no problems. the few times I noticed the injector fan turn on it was hotter outside, haven't heard it since it has started cooling off. I mean after i shut the car off as long as I turn it back on within at least a couple of minuets then it turns back on just fine. its just after a 5+ minutes it wont turn back on until the engine cools off. I havent been directly affected by this yet since anytime I turn the car off I am either done driving or my car will be sitting long enough to cool down. And I make sure to get gas close to my house before the engine gets warm so thats not a factor either. I just know that one of these days I will forget to get gas and ill get stuck in the station until the car cools off.

 

[bonfire79]

hmmmm. okay, well doesn't sound like the ignition control module is failing. that's why I asked if it died in mid-drive. these units get hot and end up shutting down, and once they cool off, the engine starts up again. I still think you should go through the FSM and troubleshoot everything in the fuel delivery system and make sure everything is working. at least you can drive it.
keeps us updated if it continues. may not be so bad now that its cooler outside.

Bon