"Some others suggest a timing issue, but the fact that you start up, and can drive for 1.25 hours isn't consistent with that idea. Timing doesn't vary like that, and while you can adjust it some with vacuum advance or retard on normal OEM Dissys, that wouldn't explain your symptoms."
My statement and still stand by that with the info we have. I suspect fuel but OP says "I have spark and fuel when the shut down occurs." So once again if it has fuel,compression and spark at the right time it will run.
Why do you feel that it is a starter problem when it turn over?
My theory is it is not the starter in and of itself. FJ4013 showed an image of his starter's Pull In Coil module and said the wire insulation was damaged, wire was exposed, and looked like it had melted, in one of his earlier descriptions on the wire that provides battery voltage to the coil once the starter Pull In Coil closes and connects battery power to the starter motor. Since current can flow in both directions, once the starter has done its job and the engine runs, the Pull in Coil module dis-engages the starter motor and disconnects the battery power from the starter motor. However the wire from the starter terminal to the coil is still energized at battery voltage, but is now being supplied from the coil's "+" terminal which is being fed via the ignition "run" position instead of from the closed starter contact.
If that exposed wire end can move, or has a frayed wire that can touch the grounded case of the Pull In Coil housing after the engine runs and heats up due to thermal expansion, or can arc to a grounded bolt head near it, that would instantly short out the hot side of the coil, thus killing his spark and shutting off the ignition system. If the arcing is intermittent that might explain the "sputtering" as it dies, it would also explain the melted insulation, and why after things cool down why it restarts. The whole thermal expansion thing might be a stretch, and I acknowledge that, but it explains his symptoms. He also mentioned in a PM that those connections on his starter have lots of corrosion and that wire connection is slightly loose, so arcing or shorting due to that is feasible.
He has since added some insulation coating to that area, though can't guarantee he fully covered the exposed wire due to space access issues, but he has since gone from the engine cutting off after 30 minutes to cutting off after 1 hour 15 minutes, and from a 15 minute delayed restart to a instant restart, so I think the problem is in this area. Again, not with the starter function by itself, but by a shorting out of the connection on the circuit from the starter's initial coil energize path to the coil.
I'm just proposing this as a theory, and his initial fix attempt seams to have improved performance and changed the situation such that I think that is the right path. I can't think of how timing would change as the engine runs to cause this. It could be a fuel issue, but how do you explain a consistent 30 minute shutdown after running with a 15 minute restart wait period before restart as a fuel issue? Also he initially had a sluggish starter spin up post shutdown which wouldn't be explained by fuel. A arc or short lowering the battery voltage would explain a sluggish starter performance if the short was due to thermal expansion causing that circuit to get close enough to ground to arc.
All theories are welcome, I just think the only thing that explains his symptoms is the coil being shorted out by a yet to be 100% verified path that seams to be temperature dependent. A energized wire at battery voltage that has exposed wire and melted insulation near vehicle ground on the starter case seams to explain his issues.
