Figure out if it is a fuel or spark problem first. Will narrow the possibilities down, make the diagnosis easier. A spare spark plug can be used to test for spark when cranking for example. And spraying starter fluid into the intake during attempted cranking can point to a fuel related problem.
Thanks for the replies so far. The problem hasn’t happened again yet with several stops and starts. It’s intermittent. It’s started immediately each time.
When something similar happened a few months ago, it turned out the battery cable had become disconnected or shorted, but I thought they fixed it - and I assume then it didn’t even turn over but don’t remember.
There is a little electric motor in the fuel tank under the trunk. That is the fuel pump. When you turn the key first to run (not start) the computer will turn the pump on to prime the fuel lines for about 20 seconds and then shut off. When you turn the key beyond run to start to activate the starter motor, when the engine starts, the computer will turn the pump back on and will run continuously until you shut the car down. The fuel pump sounds like a humming sound coming from the back of the car. So when you first turn the key to on, listen for any buzzing humming sound coming from the tank. If you don’t hear anything and the car won’t start, the fuel pump is not running. (bad pump, relay, computer, wiring, etc.) The other way is to hook up a fuel pressure gauge. But yeah, fuel or spark, which one?
Man, it happened again tonight. I tried dozens of times to start it (I didn’t hear any buzz for 20 seconds if I just turned the key on).
After 40 minutes I tried a few more times. It wouldn’t start. I went into a store and called AAA for a tow.
Went back out and it started. I don’t know about ‘sparks or fuel’, I’m just going to call a mobile mechanic and tell them about the suggestions from this thread.
Well, it seems to be solved. I did find a good mobile mechanic, and he diagnosed it as the crankshaft motion sensor. Replacing that fixed it, and it runs better also.
It’s interesting that the computer couldn’t figure out there was a crank position sensor problem and throw a code for that being a possibility. The computer knows when the starter is engaged, and when the starter is engaged the engine should be turning, and it should see a signal from the crank sensor.
Another story I told before but I had developed a slight hesitation on acceleration and took it to the shop after trying some other things. Got a clean bill of health but the next day at about 30 miles into my 50 mile commute, everything died on the freeway. I checked for codes but had none (this was my Riviera with the CRT screen and the ability to go into diagnostics to check codes). I had a spare computer and swapped that but still nothing. So called for a tow. After a while the shop said they were getting no reading, then later came out with the crank sensor that was broken. It was obvious it had been cracked for quite a while and my shop didn’t find it. I don’t know if that was 2bd or third strike for that shop but cost me a day of vacation time.
At any rate the point was that I got no fault code for a bad crank sensor on OBD I at keast.