I believe a '68 has a ballast resister. Ballasted systems are configured such that full 12V is sent to the coil during the starting event by bypassing the resister. This is accomplished by sending a full 12V to the coil when the key is moved to the start position. When the start position is released, roughly 6V is sent to the coil through the ballast resister (via the “run” position on the start switch).
I installed a ballasted Crane Allison ignition system in my '64. In this case the resister bypass had to be accomplished with relays, because the '64 has a simple start button rather than the rotary switch in the later cars. As an anti-theft feature, I installed a cutoff switch in the “run” wire between the ignition module and the ballast resister. With this kill switch activated, the car will start (it’s getting the full 12V from the start position on the switch)…and then stop the moment the start button is released (the power via the ballast resister is disconnected). If this is what you’re experiencing, I’d suspect the start switch, or a wiring problem associated with the ballast resister. Unfortunately I don’t have a wiring schematic of the '68 system, so I can’t be more specific.
Mine doesn’t, and didn’t have one when I bought the car in ‘82, though it’s Canadian delivery so is different - but I still don’t think the ‘68s, including the US Federalized cars, had ballast resisters.
Mitchell and I are on the same page. My bet is there is a supplementary inline fuel filter in the boot that is full of crud. When the engine’s not running the crud settles and briefly allows a limited flow of fuel when the engine is started. That flow of fuel stirs up the crud, which coats the element in the filter, blocking the fuel flow, pressurising the line and shutting down the fuel pump, the engine stalls and over the next ten minutes or so the crud settles again and that minimal fuel flow is restored for the next cycle, etc.
Yes, I checked the archives and my recollection was incorrect. That said, if anyone with a ballast resister is looking for a good location to insert a kill switch…it’s described above.
My old Jeep pickup did exactly what you describe, but it was crud accumulating on the “sock” in the fuel tank.
So many easy ways to check that. Pull the fuel pickup and sit it in gallon can of fuel and start the car. The condition of the fuel strainer may be a tipoff.
IIRC the fuel pump itself can also get clogged and restrict fuel flow.
I’ll throw in some shade tree mechanic … pull your #1 plug, lay it still connected on your head…( the one in the car) start it up, it will run, watch the plug fire. When it quits, turn it over again ( the engine) and look for spark… you will know where to start looking after that… I know it sounds crude, but I have isolated a lot of no start issues just this way. Your ballast resistor should be mounted on the picture frame.
Bob Do you have a full 12v at the coil when the ignition is on. The ign switches on 1.5’s have two contacts that feed power to the coil - albeit through the same wire to the coil. One operates when you are cranking. You can have a situation where the run side contacts are dirty, and the cranking side are ok. When you let the key return to the run position the coil gets starved, and the engine dies.
For that one could run the car with all 6 plugs in and when it quits pull any of the plug wires and attach it to a spare plug and crank the engine to check for spark. It would just avoid pulling and replacing a plug and the noise of running the engine with one plug out.
IMHO it isn’t electrical. Not sure anything would overheat in 5 seconds, nor would an electrical problem cure or reset itself in 10 minutes.
I believe that some very small fuel could be migrating back into the cylinders just enough for 5 seconds. Sort of when I shoot starter spray into my snow blower and it works for 5 seconds because i had dirt in the fuel line that blocked fuel from entering the carb.
I’d get a spark detector and see if the sparks continue as the engine dies and as you try to restart before the 10 minute rest stop.
At least one does. I had tried to run a Pertronix 2 without suppression core wire and it would overheat and stop working after about a mile After five minutes it would cool down and heal itself and be good for another mile. Kind of a rare condition, and all fixed now after swapping in new wires.
My point was that absent a current ready to blow a fuse, 5 seconds doesn’t seem to be enough time to cause a component to overheat. I can easily see something heating up and going bad after driving a mile or 5 minutes, but I question it causing the engine to stop after only 5 seconds, seems to be more of a fuel issue.
But I do agree, that 5 minutes may be enough to cool down an electrical, heat related problem and let you go another mile. BUT hopefully we’ll find out soon.
