Car won't start when hot

Profile picture of the author donrock by donrock Posted: 06/16/2011
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?

  • Profile picture of the author HeySal
    HeySal
    If it were an older car I'd say vapor lock. New cars - don't know.
  • Profile picture of the author Bill Farnham
    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.
  • Profile picture of the author donrock
    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.
  • Profile picture of the author Roaddog
    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
    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.
  • Profile picture of the author Roaddog
    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 jimbo13
    jimbo13
    I had this exact same problem on a car 10 years ago.

    If it was a very hot sunny day and the car had been out in the sun it would sometimes not start when I finished work.

    It was always fine in the morning as it is not exactly the Sahara round here and come 18:00 onwards it would start okay as the summer temp started to drop.

    It would also sometimes conk out if I was driving and then came to stop, such as when coming off the motorway but I could restart it whilst freewheeling.

    People laughed when I said the car doesn't seem to like warm weather so I just ignored it as summer is not exactly long here, eg it is bucketing down right now adn this is June.

    When I wanted to sell the car I thouhgt I had better take it to the mechanic so waited for a hot day and took it to him.

    It was the carburettor apparantly. Old cars had chokes so you could regulate the oxygen/fuel mix I think, like pull it out when cold and push it in when hot.

    The problem was some sensor or other was stuck on a setting that was pumping too much oxygen as though it was winter and the heat was making it not start or conk out if I drove it any distance.

    I'll bet that is the problem.

    Dan
  • Profile picture of the author HeySal
    HeySal
    Originally Posted by jimbo13 View Post

    I had this exact same problem on a car 10 years ago.

    If it was a very hot sunny day and the car had been out in the sun it would sometimes not start when I finished work.

    It was always fine in the morning as it is not exactly the Sahara round here and come 18:00 onwards it would start okay as the summer temp started to drop.

    It would also sometimes conk out if I was driving and then came to stop, such as when coming off the motorway but I could restart it whilst freewheeling.

    People laughed when I said the car doesn't seem to like warm weather so I just ignored it as summer is not exactly long here, eg it is bucketing down right now adn this is June.

    When I wanted to sell the car I thouhgt I had better take it to the mechanic so waited for a hot day and took it to him.

    It was the carburettor apparantly. Old cars had chokes so you could regulate the oxygen/fuel mix I think, like pull it out when cold and push it in when hot.

    The problem was some sensor or other was stuck on a setting that was pumping too much oxygen as though it was winter and the heat was making it not start or conk out if I drove it any distance.

    I'll bet that is the problem.

    Dan
    Dan - that's basically what vapor lock is, I believe. I had a car that used to vapor lock a lot and that's pretty close to how my mechanic explained it to me.
  • Profile picture of the author Bill Farnham
    Bill Farnham
    Originally Posted by jimbo13 View Post

    The problem was some sensor or other was stuck on a setting that was pumping too much oxygen as though it was winter and the heat was making it not start or conk out if I drove it any distance.

    I'll bet that is the problem.
    Dan,

    The OP stated - "When my 2002 Taurus V-6 gets hot it won't start. It doesn't even turn over."

    Curious...how much is the bet, I may want a piece of the action...
  • Profile picture of the author jimbo13
    jimbo13
    Heysal - I thought you may have meant what I wrote but I have never heard the term vapour lock.

    Bill - I'll buy you lunch if you come ever come to England

    Dan
  • Profile picture of the author Sunfyre7896
    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
    Roaddog
    Originally Posted by Bill Farnham View Post

    Dan,

    The OP stated - "When my 2002 Taurus V-6 gets hot it won't start. It doesn't even turn over."

    Curious...how much is the bet, I may want a piece of the action...
    You bettin on bat cables Bill? My bet is...

    Mass air flow and or a thermosensor associated with it.

    There are more than one kind of MAF, let alone how that particular car is wired. (What's inline in that circuit)


    Thee easiest way to find out is with the reader I suggested.

    Depending on how often this happens, OP should read it right after it happens...most computers that record this info reset after a certain amount of miles driven. After it's checked
  • Profile picture of the author Bill Farnham
    Bill Farnham
    Originally Posted by jimbo13 View Post

    Bill - I'll buy you lunch if you come ever come to England
    What airport?

    Here's my thought...unless the OP misspoke about the engine 'not even turning over', that is a classic symptom of a faulty battery connection.

    All the talk about sensors that produce voltage variences (which is the principle they operate on) doesn't seem to make a lot of sense unless the car has a sensor that would interupt the starter command.

    But even then we're back to faulty battery connections unless said sensor has crapped out.
  • Profile picture of the author Roaddog
    Roaddog
    Originally Posted by Bill Farnham View Post

    What airport?

    Here's my thought...unless the OP misspoke about the engine 'not even turning over', that is a classic symptom of a faulty battery connection.

    All the talk about sensors that produce voltage variences (which is the principle they operate on) doesn't seem to make a lot of sense unless the car has a sensor that would interupt the starter command.

    But even then we're back to faulty battery connections unless said sensor has crapped out.

    Your on... how much?
  • Profile picture of the author Bill Farnham
    Bill Farnham
    Originally Posted by Roaddog View Post

    Your on... how much?
    I'll buy you lunch if you ever visit Dan.

    And if I win you can buy someone a War Room membership.
  • Profile picture of the author Roaddog
    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 jimbo13
    jimbo13
    Mmm.

    I live near Heathrow and not too far from Gatwick.

    Here's a tip. If you do ever come to England don't stay in London. It is a massive rip off. Stay somewhere like Reading. It is 30min away from Central London on the fast train and you are covered for the London underground that takes you anywhere in London.

    The ticket price will make your eyes water compared with North America, but not as much as a hotel in London will!

    Dan
  • Profile picture of the author webpromotions
    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 Bill Farnham
    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.
  • Profile picture of the author Jay Moreno
    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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