Intermitent Starting Problem
If it spins over good but wont fire the problem is in the power supplied to the cars ignition. Th battery is fine. It probably did send one spark when the switch returned from start to run.
There are 2 wires supplying that power . One is hot only in start, the other is hot in run. Find them at the ballast resistor and check with a volt meter.
Year model and such would help. There was a electric choke assist mounted by the coil on 73 up models . That thing can short out internally and drink up your starting current.
^^^THIS^^^
I keep trying to tell people this. On my old Dart, there was a ONE VOLT drop through the deteriorating bulkhead.
Do TWO separate tests, which check the running ignition circuit (ign1, dark blue) or the bypass circuit (ign2, brown)
Turn the key to run, engine off. Put one meter probe right on the battery positive post, the other on the dark blue supply line to the ballast resistor, that is, the "key" side.
You are looking for a very low voltage (drop) the lower the better. If you have a "points" distributor make sure the points are closed Anything close to or more than 1/2 volt is too much, and shows a drop in the path from
battery--fuse link, through the bulkhead, the ammeter circuit, the connector at the ignition switch, through the switch and back out the connector, and back OUT the bulkhead connector on the dark blue line.
IF you show anything close to 1/2 volt or more, pull the connector apart, inspect, clean, fix
NOW check the ignition bypass, same way. One probe on the battery positive, other on the coil positive. You want 1/2 volt or less with engine cranking, USING THE KEY
NEXT hook the meter form the coil positive to ground and crank the engine USING THE KEY. You want a MINIMUM of 10V at the coil positive.
