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Bigz Zee

'75 280Z - Starts and Runs, Shuts Off after 30-60 minutes

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Posted (edited)

1975 280Z, I bought it two months ago and I just starting to sort it out.
The car appears to be fairly stock, in other words, not heavily modified.
The previous owner does not have a lot info about the car, it seems he bought the car from someone in Mississippi who did the rebuild and body work.


The car starts and runs fine, but it has konked out on me twice.
After the car is warmed up, and having driven it for 30 plus minutes, if I drive the car hard, it's starts to stumble, and then it will turn off as I shift gears.
When I put it back in gear it runs again. I can keep it going that way for 10 minutes or so before I have to pull over and park it.
So I pull over, let it cool down for 15 minutes, then it starts right up and runs fine.

The engine temperature is nominal during operation.
The points were replaced with electronic ignition. Pertronix ?
The coil is an Accel Super Stock.
Spark plugs and wires appear new and in good condition.

Here is a photo album of the car, with pics of the engine bay and close ups of the distributor and coil.
https://photos.app.goo.gl/mPAoGeADxL8qoH3U7

Edited by Bigz Zee
Posted before finishing

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A very good suggestion. See attached photos.
There is crud in the filter and it also appears to be leaking fuel.
The previous owner said the person who redid the car coated the inside of the tank, and suspects that coating is a weak point in the fuel system.
Maybe replacing the tank is the way to go. What do you think?
And how would I know if the crud made its way to the injectors? 

Thanks

IMG_20200614_092551.jpg

IMG_20200614_092604.jpg

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They used to cost about $10 so for maybe $15 I'd buy a new metal filter that goes up front before the fuel rail, passenger's side fender. Hacksaw it in half and see what you find. I very much doubt any crud would get past that filter and make it to your injectors. 

The tank liner I used was Red-Kote and you would see red slivers in that rear clear filter. That looks more like trash to me? Anyhow it shouldn't leak if you have it right out of the tank, before the high pressure fuel pump. You wouldn't want that after the fuel pump's 35-ish psi output in my opinion.

Others will chime in later about your ignition overheating. That's the 2nd issue you could have off the top of my head. Good luck. :beer:

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Next time it will not start, have a spare spark plug handy, plug the center lead of the coil to the spare plug, lay it on the strut tower so you can see it, and crank to see if there is a spark. You need to diagnose the issue to spark or fuel before going deeper.

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This is a little piece of data , but are you sure this is a 75? It would appear that you have a 77 or 78 280z. Check the drivers door jam for production date. 

This will make a difference if your looking for data or parts/ location. BTW very nice car.

 

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7 hours ago, Bigz Zee said:

 if I drive the car hard, it's starts to stumble, and then it will turn off as I shift gears.

The points were replaced with electronic ignition. Pertronix ?

In case anyone missed it.  It has a Pertronix under the cap, apparently.

Another sign of ignition problems is the tachometer needle behavior.  Watch the tach needle when the problem happens and see if it's following engine RPM or if it's acting crazy.  If the engine dies and you're in gear the needle should still follow RPM as you coast down in gear.  If it does you have spark, but no fuel.

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The VIN in windshield matches data on the door jam and the data on the plate on the strut. Engine number is not a match.

I'd like to find the person who redid this car, so I can get the details on what it is and what was done.

Zclocks, what are the pieces that make it look like 77 or 78?

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4 minutes ago, Bigz Zee said:

The VIN in windshield matches data on the door jam

What is the Build Date?  It's on the door jamb plate.

I think that 75 only had one fusible link block, not two.  Your car might be a 76.  

image.png

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Looks like the same distributor as my Z. 1/78.

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Posted (edited)
5 minutes ago, Yarb said:

Looks like the same distributor as my Z. 1/78.

I knew I should have looked at that picture closer.  Standard Nissan variable reluctor distributor.

So, probably the original 1975 ignition module which was the second year of electronic ignition.  And maybe a "performance"coil, putting more strain on very old electronics.  The module is close to the fuse box, in the cabin.  It will have aluminum fins and look very cool and space age.

The symptoms sound just like when my 76 ignition module went bad.  Rev it up to 3500 RPM, the tach needle starts reading double engine speed, and bouncing all over.  Let it die and cool off and it's okay.

Edited by Zed Head
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New Information

We checked the spark plugs, dry but black. Checked the wires through the cap, all good. Checked the timing, check.

Then I drove it 25 miles to where I've been storing it. Ran well.

Then I stopped, left it running for less than 5 minutes while we were preparing the parking spot, got back in and it stumbled bumbled and died. It did not restart, so we are waiting for it to cool down. It is hotter than usual, normally the temp is to the left of the F°.

IMG_20200614_174525.jpg

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Tach seems to operate normally, not jumpy, follows RPM as I coast down in gear.

I did the spare spark plug from the coil trick, plenty of spark.

One more point, black exhaust. I need to check compression.

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27 minutes ago, Bigz Zee said:

 

Then I stopped, left it running for less than 5 minutes while we were preparing the parking spot, got back in and it stumbled bumbled and died. It did not restart, 

 

The stumbling and bumbling after letting it sit hot sounds like the heat soak problem.  

Your problem also sounds like a bad ECU.

You should still watch your tachometer needle.  It will tell you a lot if you look at it.

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1 minute ago, Bigz Zee said:

One more point, black exhaust. I need to check compression.

Might be running rich.  That's how the ECU's die.  Run rich, kill engine.

If you have a spare ECU it would be worth a quick swap.

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I'll track down an ECU.

What year ECU?

Thanks everyone for the help. Unfortunately the car will be parked for the next two weeks before I get back to it. I'll be sure to update this post as I work through and solve this issue.

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Posted (edited)

They're expensive and that might not be the problem.  It's just a possibility.  Some of us have found that any ECU from 75-78 will work on our cars.  So if you find a cheap one at a wrecking yard it might be worth a shot.

It could also be just a wire to your coolant temperature sensor.  Or the sensor itself.  If the connection gets open the ECU thinks you're in the Arctic.

Working on these EFI systems is a process of understanding a collection of small systems and parts.  Everything is old and could be failing.  It's fun.

Edited by Zed Head
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IMG_20200502_145248.jpgOne more question.

Is there Water Temperature Switch on this car? Isn't supposed to be on the side?

Looks like there are three sensors on the front.

See photos

IMG_20200502_150122.jpg

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There are several things that are not a 75. 

1) The 75 only has 2 fuse links and yours has 4, just like the 77 and 78.

2) The AFM for 75 does not have a hose attached to the connecting boot, yours does. 

3) All of your gauge fonts are from a 77 and 78. The Quartz clock was only offered in 77 and 78(that could have been change).

4) You have a heat shield that protects the master brake cylinder.  Only came with the 77 and 78.

5) The thermostat housing has 4 ports in the front for sensors and you are only using 3 like the 77 and 78. 

 

Very odd. I have a 75, 1/75 production date, and it looks nothing like yours.

If the PO  transplanted everything from a 77-78 to a 75 shell he did a lot of work!

 

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The engine bay does have that “post 75” look doesn’t it? If the head is an N47 rather than the expected N42 on a 75, then.... With the many years of history, who knows what parts have been substituted in. 

The only concern I have is the plastic fuel filter back by the tank, but only if its on the output side of the pump. If its between the tank and the pump inlet, it’s under no pressure (vacuum actually) and should be fine. If its there, then there has to be another proper high pressure EFI filter under the hood between the Body hard line from the tank and fuel rail at the front right of the engine.

Heat soak is rarely an issue with EFI engines. I’m leaning on the ignition module failure as the likely cause. Or coil, or distributor pickup heat related failure.

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