Older Toyota Corolla Sometimes Won't Start When Hot - Continuing Puzzler

I’ve been trying to fix this problem for so long (plaintiff whine) but it continues to elude. My 1981 Toyota Corolla wagon began to intermittently fail to start when warmed up about five years ago, and by fail to start I mean all lights come on but zero crank and no clicking sounds either. The amount of time I must wait for it to cool down and start again has varied between 20 minutes and today’s record, 3 hours. This problem is common with older Toyotas and usually means the starter motor needs to be replaced, believe me I’ve looked into it, but here’s the puzzler. I’ve replaced the starter motor two times and it has failed to solve the problem. I’ve replaced the ignition switch four times, same thing. I replaced the battery thinking maybe my old battery was losing mojo, but tears came to my eyes when it happened again. I rack my brain: what could it be? I’ve studied how a hot starter head close to the exhaust manifold sees it’s resistance go up, that the initial crank requires big voltage throughput. But an aluminum heat shield is built in and wrapping the starter in a heat blocking blanket is not physically possible with my configuration. What I haven’t looked into yet is the clutch safety switch. I did receive the following bullet from a previous CarTalk query which read: “If a manual transmission, the clutch safety switch must be working and have low enough “on” resistance. Likewise with an automatic transmission, the neutral safety switch.” I would love more detail about the clutch safety switch. I can add this interesting caveat to today’s 3 hour record wait. I’ve gotten good a bump starting the car by myself. Today I bump started it in rolling reverse, re-parked it, and tried restarting again. Started right up when it wouldn’t start moments before. I feel like this must b e clue.

Are your battery cables good and not the make it yourself battery clamps. Are connections clean and grounds clean and tight. You can short the clutch switch and eliminate it.

I had a '77 Honda with the same problem. It had several connectors between the clutch safety switch and the starter lug, for various modules not included with this car. I solved it by putting in a push button start switch and piggy-backing it to the existing wire at the starter. Worked like a charm.

The 79 Corolla had the ground wire between engine and firewall. Our starting problem went away when I took the wire off the firewall, scraped the paint (on the firewall) down to bare metal and reconnected. If your car is similar, your solution may be too.

It sounds like the trouble is with the safety switch. Power from the ignition has to pass through it and on to the starter solenoid. The switch is in series with the solenoid so if the switch contacts don’t close properly when the pedal is depressed no power gets to the solenoid. You could jumper the switch connections when the trouble happens again to see if that clears the problem. You could also check the voltage on each side of the switch with the pedal depressed to verify voltage is getting past the connections. I suspect replacing the switch will solve the issue.