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Grand marquis won't start

Have a 2000 grand marquis that will not start after it gets warmed up. Recently had two occasions where after driving for about half hour and it’s shut off, it will not start. Cranks good, but will not start. After it “cools down” it will start. Have had it to my mechanic and the dealship. Thay can’t find anything ??? They say it has to get worse before they can make it better. They don’t want to start throwing parts like fuel pumps at it. Any suggestions appreciated.

If your mechanic has a dead car in front of him that won’t start and he can’t find the cause, it’s time to find a new mechanic. Have they experienced the no-start condition, or is it way too intermittent to check? You need 4 things for your car to start–fuel, spark, compression, and the correct timing. You can rule out the timing and compression since the car does run.

It should be a simple matter for any mechanic to check for spark and fuel when this happens. Fords have been notorious for ignition modules failing when they heat up. Not sure if your car is one of the affected years, but it would be a good place to start if there’s no spark.

To their credit, they aren’t throwing parts (and your money) at the problem without knowing the cause.

As said above, the first thing to decide is whether it is a spark or fuel problem. There are simple inexpensive tests a mechanic can do to decide.

Without any further clues, my first guess would be a faulty crank angle sensor. If so, it would show up in a spark test. Other likely possibilites would be faulty fuel injectors or fuel pressure regulation, which would show up in a fuel test.

One more thing to consider on hot start problems. The ECM measures the coolant temp and adjusts the air/fuel ratio accordingly. When the coolant is hot, the ECM is supposed to reduce the amount of fuel injected. But if the coolant temp sensor is faulty, that will confuse the ECM and could cause it to inject too much fuel on hot starts, then the engine wouldn’t start as the extra fuel would flood it out. Waiting for the engine to cool would allow the engine to start then. So it is consistent with your symptom.

There’s usually at least two separate coolant sensors in modern engines. One is used only for the dash coolant temp guage, and is ignored by the ECM. The other is used by the ECM. So your dash guage could be registering ok, but the ECM could still be confused because the ECM sensor is the one that isn’t working. There is usually a simple test for these coolant temp sensors, requiring just a DVM measurement.

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This sounds exactly like the problem I’m having with my 1987 Grand Marquis (which I love).
I’ll have this checked out, thanks.