Vapor lock

Have 1997 Mercury Gran Marqui

On a hot day with air conditioning running, it stalled and would not start. waited an hour and still would not start. It started the next day.

On another occasion, sitting with airconditioning running for about 30 minutes…stalled again. Started after about one hour.

I am thinking vapor lock but I thought newer cars did not experience vapor lock

I would be more inclined to to think ignition coil.

You’ve got fuel injection. That means the fuel is under such pressure that the boiling point is too high for even hot underhood temps to boil it, creating vapor lock, which isn’t your problem. Joe’s suggestion is a good possibility. If you can

get your coil off you can take it to Pep Boys and they can ohm it out- for free I think. Maybe first have’em check for codes. WRITE DOWN THE NUMBERS THAT START WITH P! Then someone here can help you more.

This car has four or eight ignition coils (not sure about which year they switched to coil on plug), failure of one of them would not cause the engine to stall. There is a good chance that it is something electronic overheating.

when it stalled the second time, I was near a gargage. The mechanic said it had a spark and could not determine why it stalled out. would that change your conclusion?

Was it running when the mechanic said it had spark?

That’s actually not always true these days because the ethanol content in the fuel lowers the vaporization point a lot so vapor lock is possible, especially on a car with a marginal fuel pump or a clogged fuel filter.

no it was still stalled; mechanic came over to where the call was stalled; he could not find out the problem but he tested it somehow and said it had a spark.

left hood up and after an hour when it cooled down it started.

am concerned about driving it as we are in our 80’s

I’d bring it elsewhere. Your car has an OBDII on board diagnostic system that may have stored some codes.

If it truely has spark and codes didn’t send me down some other path, I’d be inclined to direct my attention to the fuel pump. I’d consider “vapor lock” type symptoms to be probably a weak fuel pump. Diagnosis for that is simple, a pressure gage on the line with the pump running. “Vapor lock” on today’s cars is a symptom rather than a cause.

“Original Equipment” is not always a good thing on a twelve year old vehicle; especially if that original equipment is the fuel filter. Fuel filters are like a lot of things: they have gray areas of operation, when they age. Sometimes they work. Sometimes, they don’t.

Also check the possibility that a pulley is locking up. A/C pulley ? maybe the A/C compressor ? Or any other pulley that the fan belt goes around, the bearing in it could be affected by temp if it’s lube is old and wearing out. As the bearing siezes it tries to stop the belt and all it’s attached to, drawing down the engine rpm and idle untill it stalls.
Just an idea here but I have seen, in the past, a locked up A/C compressor fool a tech to initially think locked up engine.
But replace that fuel filter anyway as step 1 .