1991 Toyota MR2 Intermittent No-Start (5SFE 2.2L, 4Cly)

Hello,

Thanks in advance for any advise. I’m having an intermittent crank, but no-start issue with my car. Here are the basics:

-1991 Toyota Mr2
-Engine: 5SFE 2.2L
-Mileage: 207,000

I’ve already replaced the following parts:
-All ignition related relays
-Distributor Cap and Rotor (were very worn, but were also very old)
-Spark Plugs and Wires (one wire had insulation damage)
-Coil (no signs of cracks but very crusty looking)
-The Distributor itself has approx 60,000 miles on it (replaced ~3 years ago).

Summary of the problem:
For the past month the car will intermittently crank, but not start. The issue only seems to arise when the car has been driven for ~1hr and then allowed to cool down for about 20 minutes before restarting. The car has always started cold and it has always started after immediately being shut down when warm. Also, if the car has been driven significantly more than 1hr, then it will always restart regardless of how long it has been shut off for.

When the issue occurs, letting the car sit for an additional ~40 minutes will cause the problem to go away and it will start. I’ve had a hard time diagnosing this issue due to the intermittence. However I have been able to do the following when the issue occurs:

-Confirmed the fuel pump is working by jumping the test points for the fuel pump at the diagnostics connector in the engine bay. I could hear it running and could also hear fuel passing through the lines. Jumping the fuel pump did not cause the car to start.

-Pulled a spark plug wire and tested for spark. No spark was present. Next I tried disconnecting the wire from the coil to the distributor. Holding it close to the body while cranking revealed a spark. Reconnecting the wire back to the distributor and cranking again resulted in the car starting.

-The issue has happened 3 more times since and each time simply disconnecting the wire running to the distributor from the coil and allowing it to spark to the body while cranking will result in the car successfully starting immediately upon reconnecting the wire. If this is not done, then the car needs to sit for about 40 minutes before it starts.

I’m a little baffled – What should I be looking at next? The igniter and/or noise suppression capacitor? The nature of the failure leads me to suspect a weak coil or high resistance in the high voltage portion of the ignition system, but all of those components have been replaced (cap, rotor, wires, plugs, coil). Maybe the igniter is having a hard time driving the coil with the load of the other ignition components attached, and the act of sparking the coil directly to the body jump starts (for lack of a better term) the igniter?

I have a new igniter on order, but it won’t arrive for several days. Any tips/advice on what to check or theories to look at in the mean time are greatly appreciated. Thanks!

Attached is the relevant page from the Toyota Wiring Diagram Manual showing the igniter, distributor, coil, ECU, etc for reference.