After several months of sitting, my car is now running again, but here is the part I can't figure out: if I crank the engine with the key, the engine cranks but does not start. The moment I STOP cranking the key, momentum keeps the engine spinning for a bit, and then a cylinder fires and the engine often starts. It feels like it's not getting a spark as long as the engine is cranking, but as soon as I stop cranking, the spark plugs work....as if the battery has enough power for one task or the other, but not both? The car is acting like it needs a ballast circuit, or maybe just a fresh battery?
As I've read, cars with ballast circuits have an extra wire that runs from the starter solenoid to the coil to provide higher voltage while the engine is cranking; with the way my engine is behaving right now, it's almost as though there's a wire that's grounding out the ignition circuit while I'm cranking, as though I'm getting no voltage to the coil while it cranks.
More background
--The car was imported from Japan, and many hands have been poking around under the hood.
--The car was switched from SPi to twin 1 1/4 SU carbs and from electronic ignition to points. There are a lot of dangling connectors under the hood.
--I replaced the plugs, the distributor (for an electronic model), and the coil.
--For troubleshooting, I currently have a wire running straight from the fuse panel to the " + " side of the coil because the wire that had been connected was no longer giving me any power.
--Based on another thread here, I tested both the old and the new coil, and they're both non-ballast type -- 3 ohms resistance and a full 12v.
So if my entire ignition setup now is: 12v coming from the fuse panel to the + side of the coil, red and black wires from the (2-wire) electronic distributor to the plus and minus on the coil, and that's it (other than the HT wires, of course).
Some of the Haynes wiring diagrams show inline resistors in the wire that goes to the coil; even IF my car had this setup, I'm running a wire straight from the fuse panel to the coil and the coil is a non-ballast type, so it shouldn't matter.
At this point, the only possibility I can think of is that the battery is too weak to both provide a strong spark and crank over the engine. It's a weird Japanese battery with smaller-than-usual (for the US, at least) posts and connectors, so I can't just grab a battery from another car to test if this battery is shot (the connectors are way too small to put on the posts of all my other car batteries). The battery is on the charger now, as is my "portable jump starter", so I should have lots of amps for today's testing.
Has anyone else experienced these symptoms? No spark, no sputter, no sign of combustion at all while I'm cranking, but the moment I stop cranking the key, the engine sputters or starts?
