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Driving along, then nothing

Jon, the BIG boy

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This is crazy.

This morning about 5:30AM, I'm driving back from San Diego, doing about 80mph in my stock '72. Engine is purring, gauges all indicate normal. All of a sudden the engine just quits. I start to slow. I immediately press in the clutch to get max roll, the tach drops to zero, the lights are still on. I roll to the side and try to crank it. It cranks great but won't fire. After a few minutes, it fires right up. I rev it a little, it sounds fine, so I get back on the freeway.

About a 1/2 hour, same thing happens--engine stops, in with the clutch, tach drops to zero, off to the side and it cranks right up.

Fortune was smiled on me both times cuz I COULD have been stopped in the middle of a six lanes, but was lucky enough to find holes in traffic and could pull over. But now I'm afraid to take it out of the neighborhood.

Ideas? Any and all are appreciated.


Has this ever happened to anyone?

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  • 3 months later...

I would say your carbs are freezing up because of the cold temperatures your having there. You should have 2 Air inlets, one from the front of the car that takes in fresh air and one that takes in heated air off the exhaust manifold. If you put tape over the fresh air inlet and it stops this behavior then you need to replace the diverter between the 2 because its not working. I dont have a Z car and cant be sure that they work this way but I have seen this happen to several other older cars, especially if they have had an aftermarket carb installed.

Hope this helps

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I would tend to agree with the point about freezing fuel. However, it takes a pretty big cold snap for the fuel to actually freeze. (that's my way of saying I have no idea what the freezing point of fuel actually is)

Anyway, your venturi affect might cause condensation to freeze in your carbs. Does this happen when the car is warm or just starting to warm up?

Also, I noticed that you are from San Diego.. so, I'm sure the fuel freezing problem is not the case.

You might also be experiencing vapor lock in your carbs. How long has it been since you've cleaned them? Check all of your vacuum hoses and your connections on the bottom of the carbs.

When it stops again, jump out of the car and open the fuel cap. Allow the pressure to release and then try to start the car again.

Something to try, anyway.

-- Mike

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  • 10 months later...

I have had similar experiences with my 72 (stock engine). I would drive freeway speeds and the engine would cut out when at speed. To make a long story short, I finally figured out that the wires that connected to the ballast (that ceramic thing next to the coil) were being jostled loose when high winds (from those 'freeway' speeds) would pass by it. Zip ties and some electrical tape now keeps it from happening again. I hope this is your problem, because it's an easy fix!

-Brian L.

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I believe that Brian is going the right direction. If it quit quickly without warning most probably ignition related. The frosty carb idea is possible but that usually gives warning in the form of rough running and loss of power - at least that is the symptom when the airplane engine does it and it isn't always below freezing when it happens.

You should consider looking over the ignition system. Start with the basics and then go to the more complex. Coils can and do get intermittent and cut off without warning, then work again for a period of time. I have had ballast resistors get an intermittent short in the coil that is on the underside of the unit - check with a meter while you give it a tap. Check all your spade connectors in the ignition circuit for loose wires and make sure they have good contact. Also, check that the ground wire on the distributor plate is still intact and not damaged. It doesn't move much, but they have been known to cause problems as the advance plate rotates.

Just my advice and it is worth everything you just paid for it - nothing. Good luck.

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I had the exact same problem, drove me crazy. Very sporatic, hard to chase down the problem.

I first replaced the coil, seemed to do the job and ran fine for a day or two. Then went back to the same problem. Started replacing various other ignition related parts until I finally bit the bullet and replaced the entire distributor.

It's worked perfect since then.

Happy hunting.


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I know you said stock engine. But if you have an aftermarket electronic ignition (to replace the points and condenser) it's probably failing on you. Some people put 280zx distributors in 240z's. The distributor module on the 280zx fails under higher temps after it gets old. Once it cools off, it fires again and runs fine until you get down the street. I had an '82 280zx that did this. And my '73 240z did this too. (and is currently doing it, I haven't fixed it yet). Drove me nuts on the '82, until I found the new distributor module $99-$220. I didn't even think about it on the '73 until I went to change the distributor cap (thinking it was moisture). Then there it was... the wrong size dist. cap. and the little black box on the outside of the distributor. I plan to put a stock 240z distributor in it with a pertronix electronic ignition kit. In my opinion, the 240z distributor with the pertronix drop in kit is better than the 280zx distributor. And if the pertronix goes bad, it's only $30-$50 to replace. Good luck


Oh, btw, I put a pertronix ignitor in my '72 and it runs great! Get their coil too. (I don't work for them, I just respect their products)

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  • 1 month later...
  • 2 weeks later...

Well, I had this problem several years ago on my '73 240. Driving along then nothing. I had it towed across the state to get it home. Towed it to the dealer and they couldn't find anything. Started home and half way there bam, stopped again. Finally found out it was the fuel filter back by the gas tank. There is a fuel pump back there to assist the manual pump up front. Who knew? Replaced the filter and everything was fine. Just a thought. :P

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  • 1 month later...

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