Miata Turbo Forum - Boost cars, acquire cats. - Help me fix my mystery no-start (and stall) problem when hot.

I am at the point right now where I can't trust my car.

History:

Two or so months ago it died while going to the barber shop for my haircut. It was a warm day, but from memory the top was up so it wasn't THAT warm. Everything seemed to be running well until I started driving up a moderate hill. The car just sputtered out. I put on my hazards and pulled over. I tried to hear the fuel pump but couldn't I have a CAN gauge and inputs that were only transmitted via CAN were showing so I am pretty sure that means my ECU was powered up.

I sat there frustrated and rattled some wires under the dash and eventually (within a minute) it started up. I drove it to a nearby parking lot and pulled over and attempted to rattle the wires under the dash (fuel relay) again, but it never died. I drove it to the barber (25 miles there, 25 miles back) and had no issues. I drove it to and from work probably a dozen times. I drove it all over the chicagoland area without issue.

A week ago Saturday I was out running errands on a very hot day. I drove to Cabelas which was 10 miles away. No problems during the drive. CLT temperature upon shutting it down was somewhere around 205 degrees. Upon startup, it gave me some guff. It was wanting to stall out on me. I drove around in the parking lot for a minute or two letting the fans cool everything down. AITs were very hot at first. I drove towards home but stopped at a sushi place not far from my house. I ate pretty quickly and was out in less than a half hour. When I went out to my car, it started but wanted to stall out on me again. I attempted to baby it onto the street to drive home, but it stalled before I got onto the street. I sat there in the exit to the parking lot for about five minutes. I pushed the car into a parking spot and spent the next half hour troubleshooting best I could. Again it was too loud for me to really tell if my fuel pump was turning on. I decided to bypass the relay and fashioned a jumper out of some spare stuff I had in my car and jumped the fuel pump in an attempt to see if the relay was going bad. No start.

I then called for a tow truck. it took about two hours from the time I got out of the sushi place to when my tow truck arrived. When it did, my car started and I pulled it onto the flatbed myself. I still didn't trust it enough to drive it home.

Every time I have checked it since it has started fine, but I don't trust it enough to drive it right now.

So, I am trying to figure out what things I can do to troubleshoot this. It's getting a full fuel system upgrade in the near future including pump, upgraded relays, etc, but I would really like to be able to drive the car before then.

Any ideas?

Fuel pump is upgraded DW200, only about four or five years old. Maybe 40,000 miles. Fuel level was about 1/4 tank when this happened.

One thing that was interesting was I noticed when I pulled the "fuel" fuse in the engine bay, my main fan sped up quite a bit. The fuel pump shouldn't have been getting any power or pulling any current because the motor wasn't cranking or running, so what could have been pulling so much current on that circuit? I feel like that may be related.