I live in fla and i have been having this strange no start situation with my 86.5 928.When the engine is cold it starts no problem.If the weather is cooler it will start every time but if the weather is hot like it`s been the past few days it will not start.Now to start it i will remove the tool panel in the back and disconnect the negative battery gable for a min or two connect it and will fire up right away and continue to do so for the rest of the day but sometimes it will not fire again the very next time i turn it off.Has anybody had this happened to them before? So far i have changed aii the major relays.temp II sensor,cleaned every wire and gable going from the battery to the rest of the car,all the ground points on the body and engine.and it still wont start.

 

Next time it does this, see if you can verify spark or fuel (pull a plug, see if it's wet). Then buddy-up with someone who will swap computers with you...sounds like a break in a solder joint on the PCB.

(otherwise, I would have guess Temp 2)
Mark

 

There is no spark every time it does thisand like i said it does it when the weather is hot over 80F

 

Your no start could be caused by a lot of things. Corroded connections heat up, resistance goes up, voltage drops. I suggest cleaning all your module contacts, including the ignition final stage (two plugged module under the black plastic in front fo the radiator). Also, pay attention to the positive termanal at the battery. The multiple connections from there go to the 30 bus for fuel and spark. You need these connections to be clean too!

 

Relays are easy... swap the LH relay and see if that helps. Had a similar problem a few years ago, same model year.