1978 280Z barn Find / sons dream car won't stay running

[kelly969]

My son purchased a 1978 280z.  He is 17 and not a mechanic.  Of course we have a mechanic; however, he is younger than the car.  The Z was sold to my son.  It was in a barn for approximately 10 years.  My mechanic is honest; however, this vehicle is challenging.  At this point and time, the vehicle starts and shuts off after minutes.  The cold start valve has been replaced among other things.  At this point we are working on the ignition coil and a part that cannot be identified,  I read post and yet have not  located this part to purchase.  Please let me know if you know what it is.  I have heard distributor condenser, ignition capacitor...at this time it cannot be found. The capacitor I purchased had one wire.  This part has two. Please help.

 

No I am not a mechanic but I am intelligent enough to understand parts on a vehicle. So please help and not belittle.

[Zed Head]

That part is a capacitor, AKA condenser.  The one wire units ground through the case and mount, the two wire units have a separate ground wire, as yours does.  But they both do the same thing.  If the engine starts that's not likely to be your problem.  If it was shorted, you'd know it because it would short whatever it's connected to.  I wouldn't worry about unless you've measured continuity and know that it's shorted.

If the car sat for ten years, you'll need to give many many more details on what's been done to it before you tried to start it.  The gas tanks on these cars aren't well sealed and tend to get rusty after just a few years, let alone ten.  The fuel pumps get rusty, the injectors get clogged, the filter could be full of water.  Who knows.

But since it does start and run for a short while, describe what happens as it dies.  Does it just shut off quickly, or does it slowly lose idle speed and die?  Will it restart immediately or do you have to wait?  If ti won't restart, does it not have spark or not have fuel?

The more detail the better.  You can't just replace parts one at a time on these cars, you need to do lots of testing.  Check the forum's Download section and get the 1978 Service Manual and the 1980 Fuel Injection Guide.

[Dave WM]

You are going to need to either become a mechanic or find one that knows about older cars. The good thing is the 280z has a very easy to understand EFI system. Like Zed Head says you need to give a lot more details. For starters you need to get a fuel pressure gauge to monitor the fuel pressure. Next you need to confirm the ignition is not the issue. I too doubt the condenser has anything to do with the issue, its prob more for noise suppression than anything else since there are no points to burn up. The fuel injection guide will show you how to check things out. When it dies does it start to backfire before? does it run rich (look at the plugs)? does it start right up after die? these will give some clues. Generally speaking you need to make sure you have no air leaks, good electrical connections and grounds, good fuel pressure and flow. Replace the temp sensor for the EFI (this is one that can give trouble if its not right, you can check it with an ohm meter and know the temp) there is one for the temp gauge as well, may as well replace that one too. Check my You tube on Dave WM I have a few videos in there that relate to Z cars that may help, like how to check temp sensors and fuel pressure.

Edited May 29, 2016 by Dave WM

[kelly969]

At this point, I have no thoughts of being a mechanic; however, I told my son he should definitely give it a whirl. He is 17 and chose a non running "dream" vehicle as his first. Everything being done is his $. Our mechanic is trustworthy and all techs for datsun's ask for 300 just to look at it.  I am the researcher.

Info that you asked about, it just dies. The longest it ran was five minutes. Fuel filter, pump, afm and hoses, cold start valve, just bought ignition coil and a part that I thought was the one pictured but it only has one wire and a larger cylinder. 

As for gas tank being an issue, my mechanic did bypass the gas tank and results were the same. Being that it sat for a long time, we have been using premium gas during trial and error. I will say we have a mechanic younger than vehicle. With that being said, his father is a mechanic as well and enjoys working on it.

 

[kelly969]

Also, we cleaned fuel injectors and replaced spark plugs. I think that is when it started and ran for less than five minutes.

[kelly969]

Going through paperwork, it fired and ran after injectors were cleaned, spark plugs replaced and distributor cap and rotor installed

[YoshiDori]

So does it start right back up after dying?

[esmit208]

Your son is about to learn how to truly be a car guy. I had the same car which I believe was one of the early models to get EFI and electronic ignition. The ECM (engine control module) is just behind a kick panel on the drivers side footwork if the panel is still there. The model I had developed a water leak just above the panel under the dashboard. My car sat for about 7 years also. I initially thought it was a bad connection on the harness that connects to the ECM itself. The car I had would run fine and then intermittently would begin to misfire on 3 or 4 cylinders. It is almost impossible to get an ECM to run a test for your symptoms unless you pay the going rate for one. The electronic systems on the early cars were rudimentary to put it mildly and required a patient owner to diagnose any issues. Check to make sure there does not seem to be water intrusion in the area behind that kick panel covering the ECM computer. As this computer nears the end of its life it can cause basic running issues. If the signal between the ECM and the ignition switch is weak or gets intermittently interrupted the symptoms you are describing could likely occur. The fuel injectors receive a signal from the ECM. Mechanically the car will keep going and any part you need you can get. Many owners of the early EFI models just got sick of the electronic issues and converted them back to carbureted models. This too can begin to chew into your college fund but just suggesting another option. My guess is there has been some water intrusion in the windshield wiper cowl area under the dash. If he pulls the carpet back our out on the driver's side footwell chances are there has been enough to affect the ECM. If not it will at least put your mind at ease. Remember these machines just need TLC and a patient owner. Just remember you are not really a CAR GUY unless you can work on it. This too will give him valuable experience when he steps up to more complex machinery. GOOD LUCK and let us know how you make out.

[Zed Head]

The Engine Fuel, and Engine Electrical chapters of the FSM, and the Fuel Injection Guide (1980 version) are the place to start, with a multimeter.  Don't assume anything, almost every component can be tested before replacing.

This should be called the Fuel Injection guide, not EFI Book - http://www.classiczcars.com/files/file/32-efi-book-1980/

Here's the FSM - http://www.classiczcars.com/files/file/24-1978-280z-factory-service-manual/

Here's all of the Downloads - http://www.classiczcars.com/files/

[Dave WM]

My guess would be poor electrical connecters. EVERY one should be checked, also the grounds including the main ground from the ECU (goes to the battery terminal) I would start with new battery cables as a min if you don't have them already, then check all the body grounds (undo them look for corrosion). check fuse links for corrosion, and check all the sensors per the FSM. The system is very simple and works very well, good diagnostics should find the issue once you get all the connections checked out.

Here is me working on the battery. jump to 1:28 talking about battery

 

Edited June 5, 2016 by Dave WM

[siteunseen]

When you're trying to crank it next time, have someone pinch the fuel line after the fuel filter.  If it's soft you have a weak fuel supply, it should be almost solid feeling when under pressure.

Here's some good information on just about everything pertaining to a 280.

http://atlanticz.ca/index.php/tech-tips.html

[kelly969]

@YoshiDori It starts up immediately after dying only on occasion. Sometimes you do have to wait a couple minutes. When son tried to start it himself it started up back to back but only ran for a couple seconds and the running was very choppy and it died off.