No spark on hot days

[Xenn]

When my car sits out in the sun for too long, it will crank but not fire, I hooked up a timing light and it would not flash so I know it is a lack of spark, Ignition coil is new, distributor and alternator are both new upgrades/swap (new 280zx parts wired in) so the ignition module and voltage regulators are both good, when the car cools down (the interior) it will start just fine. Any Ideas? (My only guess is a random separating connection or dieing ECU)

76 280z

Edited June 5, 2013 by Xenn

[Pop's Z]

Xenn, if you have a 280ZX dizzy check the ignition module. They can be affected by heat soak. I always carry a spare just in case. The module came on a variety of Datsun cars so next time you are at the junkyard pick up a few for spares.

Cheers, Mike

[SteveJ]

You can cool off components using a can of dust-off or similar product. Just hold the can upside down when spraying on the component (such as the ECU), so you spray a liquid on it. The liquid will evaporate quickly, cooling off the component. That will help with the diagnosis.

[zKars]

First ID the source of the failure at bit.

The + side of the coil needs +12 when you are cranking and running, so check it when running, and when failed. If you have +12 at the coil + terminal, then move to the "B" terminal on the ign module and check there. This checks the wiring between the coil + and "B". If no problem found, then you its not likely your wiring that supplies power to the coil. To confirm, hook up a jumper wire from battery + to coil + and see if it fires. If it does, take the jumper off and see if it still fires, maybe the "problem" cooled down and works now

That's about all you check with a generic Volt meter. You can't see the signals on the - side with a voltmeter.

Failure is likely either the ign module, coil (least likely if new) or the signal pickup coil in the dizzy itself. Take the module off the dizzy and remove the two little spade connectors that connect the module to the internal pickup coil. Check for good connection and dirty contacts. Clean and replace. Check, clean, re-crimp and continuity check all your wires from coil to module.

If the failure is predictable, immediate, and repeatable (works fine after cool down everytime), my bet is on the ignition module too.

[Xenn]

The dizzy is new, not a junker, however ill keep a can of CO2 in the car to check if its the relay or the ECU that is getting too hot, ill also pick up a spare next time I head out to a pick-n-pull.

zkars, I will surely try your direct connect battery to ignition coil next time it happens, my guess is that is before the ignition coil, that would easily prove/disprove it.

All the wiring between the distributor and ignition coil is new and soldered/heat shrunk, fresh spades, all that jazz, whenever I rewire something I try and do it right, ive had to replace too many "twist and electrical tape" faults in the car already.

The big problem is it only happens at the hottest part of the hottest days (IE when im trying to go to lunch at work), so there is not much I can do when it happens, it is also very intermittent, only happened a few times, the first time I thought it was my ignition coil finally dieing so I got a new one and after installing it an hour + later it ran, however it happened again later with the new coil.

Thanks for the feedback.

Edited June 6, 2013 by Xenn

[Captain Obvious]

I would like to drop back just a little and double check something...

A lot of 280's have hot start issues and it's usually fuel related. I know you said there's no spark when this problem is occurring, but are you positive, no question, absolutely know for sure that it's an electrical problem and not a fuel problem?

Are you sure that the timing light while cranking is a good indication of spark? Did you try the timing light when it's NOT hot and get flash?

[Xenn]

I have before, I will double check to make sure I am not remembering incorrectly, also, my fuel pump is wired into a separate circuit that kicks on when im on ACC from when my AFM was dieing, so I can hear my pump going.

[Xenn]

Problem solved I believe, dieing fuse-able links. If it happens anymore ill post again.

[Xenn]

I take that back, the problem simply hid, this morning it would not start when cold, so I connected the coil to the battery and barely got it to start, got it to work, now nothing, so I am going to head back and do a battery of tests, volt meter, timing light, starter fluid, go rent a fuel pressure gauge, all of that jazz, So I would list heat as only an exacerbator of the problem, not the cause since it was cold this morning, hopefully I can get it running and home to work on more.

Also a thought I had, can you burn out ignition coils through having too high of a voltage run though them? My volt meter reads ~15 when running, I always figured it was just adjusted poorly (since it says like 13 when off) but It would be nice to know if it was a possibility.

[Zed Head]

You never said if you have a ZX distributor or the stock 1976 unit with the ignition module in the cabin.

And the voltmeter in the dash is often wrong. Mine (1976) read high until I adjusted it. Your other voltmeter will tell you how close it is. But, to your question, yes, high voltage can damage electrical components.

[Xenn]

Should both terminals have 12 volts on the ignition module?

[Zed Head]

The 1976 Federal model ignition module has seven terminals.