I've got a strange one. My 73 is pretty stock. It does have an aftermarket crane ignition, but I can't see how this would cause the following problem.

When it hasn't been started for a few hours, and the engine is cooled to the ambient 90 degree air temp, the first two or so times you turn the key, the starter behaves as if it isn't getting enough power. It sounds like the battery is almost dead, and simply cranks slowly. On the third try, the starter cranks normally, and the engine starts fine.

If the engine is hot, this problem won't happen. I've read up on cleaning the electrical connections between the battery and the starter, done that, no change. I'd really hate to buy a new starter and still have this problem, but that seems to be the next thing to try. Any thoughts?

If you are confidant that you have addressed all the external electrical connections, the only iffy bit left is the starter.

See if you can arrange with an Auto Electrician to have it bench tested.

If it is the original starter it might just be worn brushes.

At least they are reasonably easy to remove/replace.

Your ignition timing may be too far advanced. Grab a timing light and check. The distributor might have slipped or been set wrong.

The 240Z starter is pretty easy to take apart. The are details in manuals outlining how to inspect and refresh the contact surfaces. (commutator). The not-so hard part is geeting the brushed to slide on during reassembly. Just twist your tounge and it go back together. Be sure there is no oil inside the starter. (From a leak) Oily starters die early deaths.

I'm betting it's igntion timing.

Jim

Edited August 27, 200816 yr by JimmyZ

Cleaning the connections and battery cables may not be enough. Check to see if the battery cables need to be replaced. If they are old, replace them. I did so and all of my many electrical problems were eliminated. Just take measurements and go to NAPA. I even got a cable with a built in wire for the ground at the firewall. Be confident that these cables are good before tearing into other components. (I speak from sad similar experience).

Thanks guys for the help. I'm too busy to try out anything, what with Gustav about to clip us, and Hanna staring at us. I'll just park the Z somewhere high and dry for a while.

Problem solved. It was not electrical, it was timing. Decided to do a complete tuneup, including valve adjustment. Valves were way off. After valves, checked timing.

Timing was so far advanced that the early spark was forcing pistons back down before reaching the top. Essentially, the engine was fighting itself. Once it got running, the pistons had enough momentum behind them to complete a full cycle, I guess. I'm still surprised that it ran at all, much less ran as good as it did. Had to remove the distributor turn it and re-install to get the timing back to where its supposed to be. Previous owner had installed an electronic ignition, and probably put the distributor in wrong. After that, adjusted the carbs per Ztherapy video.

The result is the car seems to breath better, has more power, and is much smoother at low RPM. Previously it was a bit lurchy when driving slow at low RPM. It also now fires up easily. Me happy now.