Car won't start when hot

by donrock 49 replies
Being as how there are so many smart people here maybe I can get answer to this problem.

When my 2002 Taurus V-6 gets hot it won't start. It doesn't even turn over. After it cools down it starts and runs fine. I suspect a sensor or module that heats up but can't find anything about this. I had an Tempo about 10 years ago that did the same thing and it turned out to be some kind of sensor. Anybody have any ideas about this?
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  • Profile picture of the author HeySal
    If it were an older car I'd say vapor lock. New cars - don't know.
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  • Profile picture of the author Bill Farnham
    Originally Posted by donrock View Post

    When my 2002 Taurus V-6 gets hot it won't start. It doesn't even turn over. After it cools down it starts and runs fine.
    It sounds like your battery cable to ground needs a cleaning.

    Pull the terminals off your battery and clean the cable connections (both + & -)

    If that doesn't work clean the cables where they connect at the starter and/or frame.
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  • Profile picture of the author donrock
    The battery is new with newly cleaned connections. The problem is not connected to power or fuel as it starts easily when it cools down for approximately 30 minutes. It's got to be something like a sensor or module or something similar that that fails when hot but works fine when cool. I had a Ford sometime ago that acted the same and it was a bad sensor. Its been too long for me to remember exactly what it was.
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    • Profile picture of the author Roaddog
      Checked any of your sensors like mass airflow?
      Any car after 1996 uses the OBD 2 scan system, they have come down quite a bit in price and well worth it IMO. A little over $100.00 depending on models.

      It will read out trouble codes for any of your sensors.

      If you do buy one make sure you get one that can download data updates from the net (usb)

      They may all have them now, it has been awhile since I bought mine.

      Invaluable.
  • Profile picture of the author donrock
    Roaddog,

    Is that air mass sensor something that would shut down the starting but not affect the electrical system when it got hot? When I turn the key nothing happens until it cools down then it starts and runs fine until I shut it off again. Then I have to wait 30 minutes again.
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    • Profile picture of the author Roaddog
      Originally Posted by donrock View Post

      Roaddog,

      Is that air mass sensor something that would shut down the starting but not affect the electrical system when it got hot? When I turn the key nothing happens until it cools down then it starts and runs fine until I shut it off again. Then I have to wait 30 minutes again.

      donrock,




      What i would do is buy that OBD II scanner (the plug in is universal after 96, hence the OBDII) it is far cheaper than a mechanic.

      It will give you a code or codes that you translate thru the scanner manual.

      It does sound like a sensor or modules are bad. But in what I can't tell you without having/knowing the electrical/electronic system on that model.

      It's an easy plug in, and read out.

      If you do that and get a code I might be able to help you.

      Todays systems can be complex, it will save you a ton of time money and guess work in the end.
  • Profile picture of the author Sunfyre7896
    Since you said it was only when it's hot, I found this. I'm not sure it is this but I've heard something similar.

    Major vacuum leak (An open EGR valve, disconnected vacuum hose, PCV valve, etc, can create a large vacuum leak and allow too much air to be sucked into the engine. This will make the air/fuel mixture too lean and make the engine hard to start. Engine will usually idle rough if it does start.

    The EGR stands for Exhaust Gas Recirculation. It has to do with HOT gasses in the exhaust. I would look into your EGR or a vacuum leak problem. Just something to eliminate.
  • Profile picture of the author Roaddog
    Most and I mean most problems on 'modern' auto's stem from the emissions systems.

    But I'll tell you OP should find out because one of the reasons they would interrupt starting is to prevent damage from rich running, to other sensors, including oxygen sensors, and to the cats and on down the chain. Supposed to have a dummy mode though.
    • Profile picture of the author Bill Farnham
      Originally Posted by Roaddog View Post

      Most and I mean most problems on 'modern' auto's stem from the emissions systems.
      Let's not kid ourselves here.

      Most problems on 'modern' auto's stem from a loose nut behind the wheel.

      Probably not the OP's problem however.

      P.S.

      I had to change my earlier post because I see 'someone' already is a WRM.
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  • Profile picture of the author webpromotions
    Maybe bad starter solenoid.

    Find a long enough heavy wire, turn the key on, use the wire to bypass the solenoid and see if it starts up.
  • Profile picture of the author Jay Moreno
    yep i had exactly the same problem - i had a relatively new battery and connections too - turned out to be a problem with the battery connectors...
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  • Profile picture of the author boorack
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    • Profile picture of the author Roaddog
      Originally Posted by Doug English View Post

      Maybe bad starter solenoid.

      Find a long enough heavy wire, turn the key on, use the wire to bypass the solenoid and see if it starts up.

      Could be an over heating solenoid...although I thought they took care of that years ago on most cars with a simple heatshield






      Anyway I was just reading that the TFI/PIP modules (which is the ignition mod) on Fords is pretty well known for this.

      This will also read a trouble code so...back to the reader.


      last guess ..you need a reader
  • Profile picture of the author Kurt
    I'm with Jim on it being a sensor.

    My next guess is a fault in the ignition wiring system or for the sensors. It may be a connection and not the sensor itself. We know heat expands things, including the gap between things, such as in connecting wires. It is possible that if the temp rises, this gap becomes too big and doesn't conduct juice.

    I doubt it's this, but try anyway, since it's the easiest: Check your fuses for a slight crack.

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