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Pulled engine last week, put new one in last night. Will crank, and occasionally fire up strong while key is forward, but immediately shut off when the key is released. No backfiring or stumbling. Other times will just crank and not fire at all. The timing marks are spot on at TDC. Plenty of fuel with 5.5 psi at the carb after the regulator.
There is 12.4 volts at the solenoid, 7.9 volts on the positive side of the coil, 11.1 volts on the hot side of the ballast resistor and 7.9 volts on the other side of the ballast resistor all while key forward in the run position. I cannot see if there is spark or not at the plugs.
It is acting like a bad ballast resistor, but before I start throwing parts at it, I'd like to rule out anything else I might have missed or forgotten.
Engine ran perfectly when pulled out last week. Never had this happen on a fresh motor before and I'm completely stumped. Ideas?
Almost sounds electrical related like your key is acting as a "kill" switch when released to the run position and when you hold it forward as if starting it, you're supplying the necessary "ground" to keep it running. Are all grounds back in their respective places?
Will crank, and occasionally fire up strong while key is forward, but immediately shut off when the key is released.
If you can, try and run a wire so as to connect the 'resistor' wire either side of the switch.
Or, 'borrow' the ballast resistor, if that's what you have, and connect it to a temporary wire from the battery positive to the coil positive.
(If you do this test, start the engine immediately after fitting the wire, and remove the wire from the battery immediately after shutting off the engine.)
This test should determine in seconds if the switch is faulty or not.
Almost sounds electrical related like your key is acting as a "kill" switch when released to the run position and when you hold it forward as if starting it, you're supplying the necessary "ground" to keep it running. Are all grounds back in their respective places?
There's no grounds, only live supplies on those two switch positions.
That's correct, the solenoid is grounded, as is the starter, but neither get live power when the key is released, and are thus not part of the key switch context.
I guess I was confused where you said that there is no grounding taking place when the key is in those two positions, (as in the start position and the run position), because there is grounding of the starter solenoid, and of course the starter in the "start" position.
Turned out to be a weak connection on the plug between the distributor and coil! Cleaned 40+ years of crud out of the connectors, pinched the blades a little tighter, fresh dielectric grease and all is right in the world.
