Bad coil?

[rhands]

I'm at my wits end concerning my car and this gremlin. I have a 72 240z with a stock 2.4 4 speed and su carbs. The car will stop on me from time to time for a while now. I can always tell when it's about to happen because the car starts running really bad after deceleration on the freeway or similar circumstances. I have had the carbs adjusted/floats sync, new distributor, new fuel pump and spark plugs. The car acts as if it's running out of gas prior to it stopping and once it stops it will not fire back up for about 3 minutes it just cranks. Once it comes back to life, it runs as if it was flooded or misfiring. Any ideas concerning this?

[justin260z]

Fuel filter possibly?

[rhands]

I changed the filter a couple of times with clear filters to see any debris- nothing was found or did the car run diffrent.

[Walter Moore]

It could be a coil or a loose wire.

I had that problem twice after I first installed my electric fuel pump, but I changed some of the wiring so that the "cranking" voltage to the pump would always be 12V and the restart problem went away. Eventually it stopped and I don't know why. (I hate that..)

Back to your problem. It could be a bad coil I suppose. If one of the windings is broken, and only makes contact when it is "cold", then opens at some temperature. After being off for several minutes it would cool back down and work again for a while.

Coils are cheap, and easy to change.

If you have a volt/ohm meter check the resistance of the coil (ignition off) both hot and cold. It should be about 1.2 - 1.5 ohms if I recall correctly. (assuming it is stock)

0.7 ohms if you have done the ZX distributor conversion and are using a ZX coil.

[Seppi72]

Back when my '72 (currently undergoing rebuild) was new, I too was afflicted by this infrequent gremlin. My recollection is that it would happen mostly after driving in rain, which makes me think it is electrical in origin, but it also happened in dry conditions. This happened in both freeway as well as in-town driving.

The symptoms were that I would lose what felt like one cylinder. Then, perhaps 10 seconds later, I'd feel another one cut out. When the third one would go away, I'd pull over and shut it down.:stupid: The car would crank, but it would have to sit for 10-30 minutes before it would fire up again. There was no after-effect upon firing; e.g, black smoke.

I was never able to identify the source of the problem. It just became something I learned to live with - like the ignition key locking up.

I have not had this problem in the 6 years that I've owned my second '72 with the Rebello L28 and Pertronix ignition. But, the ignition key thing - oh yeah...

[rhands]

I replaced the coil yesterday and the car drives like it's brand new! I was sure that the coil was not the issue because everyone believed that coils generally do not goo bad or if they do- it totally goes bad. I was planning on a 2.8 turbo conversion but now that I feel what the car can do I'm going to wait awhile Thanks guys