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

[Bigz Zee]

1/75

[Yarb]

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

[Zed Head]

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 June 14, 2020 by Zed Head

[Bigz Zee]

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°.

[Bigz Zee]

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.

[Zed Head]

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.

[Zed Head]

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.

[Bigz Zee]

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.

[Zed Head]

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 June 14, 2020 by Zed Head

[Bigz Zee]

I have a friend with a spare, I'll do a test with that.

And I'll work my way through the EFI bible, checking the temp sensor and connection.

[Bigz Zee]

One 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

[zclocks]

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!