94 Ls 400 Cranks When Hot-Won't Start

[Larry W]

I posted this problem last week after having a new A/C evaporator installed. Car starts fine when cold, but will not restart until it cools off. Runs great with no sputtering, misfires, or rough idle. Some of you posted that it was the temperature sensor. Would the mechanic have removed the top of the engine cover to service the evaporator? I thought this unit was all under the dash? Is it possible the ECU has a loose connection under the dash since he had to unplug the wiring harness to install the evaporator? Can't rely on the car until this problem is corrected. NO codes are appearing and NO overheating. I may have to take the car to the dealer (hate that thought). Please give me more ideas to try. The temp sensor is not expensive so I may try that this weekend.

[Hanging In There]

I don't know exactly what's wrong with your vehicle but I had the same issue with another vehicle some years ago and the problem turned out to be a bad power relay that dropped out when it got hot and would not re-engage until it cooled. Replaced the relay and viola', problem solved. Good luck!

[curiousB]

As you say temp sensor is not too expensive so you can try swapping that. I am not so sure that will fix the problem though. I failed sensor or loose/corroded wire would likely result in a out of range reading to the ECU and it would throw a code to the log. You said there are no codes so the sensor must be within a valid range. (maybe incorrect but within the valid range).

These cars are notorious for ignition problem when one distributor fails and knocks out half the cylinders. That would surely make starting difficult. You might want to selectively pull a plug wire one at a time and see if the engine gets rougher when you do that.

I had a Volvo years ago that every once in a while when starting the engine would flood itself and wouldn’t start. The trick to fix it was to remove the fuel pump fuse and crank it a bit to flush out the cylinders and then reinstall the fuse and it would start right up. Not really a fix but if this worked it might lead you down the path of the fuel system.