Car won't start when hot

by 49 comments
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?
#off topic
  • Profile picture of the author HeySal
    If it were an older car I'd say vapor lock. New cars - don't know.
  • 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.
  • 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.
    • 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.
    • 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.
  • 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...
  • 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.
  • Profile picture of the author donrock
    Roaddog,

    I agree that going to get a free diagnosis is not that great of an idea. I have a 2000 Ranger and the 2002 Taurus so I just got the regular one without the CAN feature. I got it on eBay for $35.00 including shipping. If I was going to use it a lot I probably would have went for a better one. Will keep you posted on this.

    Thanks,
    donrock
  • Profile picture of the author ocvseo
    Originally Posted by donrock View Post

    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?
    the sensor is under tube beside your Radiator, try to replace that,there are two sensor you have to replace, thermostat and the overheat sensor, and also try to drain the old radiator coolant and clean it.
    • Profile picture of the author ThomM
      I'm going with the coolant sensor, it should be by the first spark plug.
      I don't remember the technical name for it, but when you turn off your engine the engine temperature raises a lot.
      Sounds like the sensor is reading that as an overheated motor and the computer is disabling the starting circuit till it cools down.
  • Profile picture of the author dagaul101
    I think your initial gut instinct about the internal thermostat might be right
  • Profile picture of the author Mixengineer
    A word of advice, take it to a trusted mech asap. I didnt and tomorrow morning im gonna find out what the damage is. The people at honda opened my hood and dropped a jaw. Gonna cost a pretty penny. Although mine was more than just heating, but it could have caused the other issues.
  • Profile picture of the author seasoned
    Wouldn't a sensor show up in a light on the dash? Fuses are a good bet though. I had a WEIRD problem with my 1992 VW Jetta! SAME symptoms! It wouldn't start when it was hot! The REASON? The STARTER MOTOR was BELOW the engine, and subjected to a LOT of heat. There was actually a field service replacement instruction(I forget the actual term, but it is short of a recall but close), to put in a heat shield. Once that was done, the problem vanished. USUALLY, at least when I was a kid, the starter motor is above where more of the heat has dissipated and air can flow over it to cool it.

    Generally, various components CAN be affected by heat, if they are sub par or run past spec. They include electronics, but can EVEN include the engine block, or gasket. Of course, if it were the engine block, or gasket, it WOULD try to turn over. My starter motor problem also prevented it from turning over. BTW it took maybe 7 years for my starter motor problem. Also, *I* generally have battery problems in COLD weather! Of course, when I say cold, I mean COLD!!!

    If you have had the same problem before on the same make of car, have them check it out. My mother once found out about an "sensor", on her car, that was setup to fail every so many thousands of miles. IT just lit an "idiot light" on the dashboard. The idea was to get you to come in, but they also originally charged almost $100 to replace the part. People called it a scam, so they eventually offered it for free.

    Steve
  • Profile picture of the author copius
    If the engine cranks over but doesn't start, it is either a fuel or spark problem. If the engine doesn't crank over then there is a restriction of power going to the starter or the starter itself could be faulty.

    If the engine doesn't crank over, I'm thinking a bad ground somewhere. Check where the ground cable attaches to the engine block.

    Another possibility, although very rare, is the neutral safety switch which keeps the car from starting in gear.

    I'm not sure about Ford products but the GM key has a chip in it that will keep the car from starting but that usually isn't affected by heat.

    I'd love to hear the solution to this problem.
    • Profile picture of the author seasoned
      Originally Posted by copius View Post

      If the engine cranks over but doesn't start, it is either a fuel or spark problem. If the engine doesn't crank over then there is a restriction of power going to the starter or the starter itself could be faulty.

      If the engine doesn't crank over, I'm thinking a bad ground somewhere. Check where the ground cable attaches to the engine block.

      Another possibility, although very rare, is the neutral safety switch which keeps the car from starting in gear.

      I'm not sure about Ford products but the GM key has a chip in it that will keep the car from starting but that usually isn't affected by heat.

      I'd love to hear the solution to this problem.
      Chips CAN be affected by temperature if sub par.

      Steve
  • Profile picture of the author donrock
    Thanks to everyone for all your advice. I'm waiting for my diagnostic scanner to be delivered and will report back when I've had a chance to use it.
  • Profile picture of the author donrock
    Roaddog;

    I got my diagnostic scanner and used it on my car. It said there were no codes. I decided to get the car hot and try it then. It still said no codes. After my car got hot it decided not to start by sounding just like a dead battery. It tried to start then just clicked. It had done this before then started when it cooled down. This really baffles me do you have any other suggestions?

    donrock
    • Profile picture of the author Roaddog
      Originally Posted by donrock View Post

      Roaddog;

      I got my diagnostic scanner and used it on my car. It said there were no codes. I decided to get the car hot and try it then. It still said no codes. After my car got hot it decided not to start by sounding just like a dead battery. It tried to start then just clicked. It had done this before then started when it cooled down. This really baffles me do you have any other suggestions?

      donrock

      If there are no codes, then it must be mechanical.

      In this case I would go with what Bill said and make sure that all cable's are contacting by physically removing them and cleaning, including the neg on the block and pos on the alt.
      Plus an (ohm), resistance check on the cables themselves when hot.

      If that doesn't work get your alternator checked.

      The way you described it sounded too consistent ie: heat and then no start, to be mechanical.

      You got a good deal on the scanner, and I'm sure it will come in handy.

      The cause could also be an overheating starter solenoid, although like I said I thought that prob was taken care of on most cars long ago.

      Depending on how good you are with mechanics, you may be stuck taking it to a trusted mech.

      It's almost impossible to diagnose over the net.

      I read that, that model is known for the ignition module doing what you described, but it should give a trouble code.

      Good luck and I would take it to a mech before you spend a ton on guessing. (after cleaning contacts)


      Jim
    • Profile picture of the author Bill Farnham
      Originally Posted by donrock View Post

      Roaddog;

      I got my diagnostic scanner and used it on my car. It said there were no codes. I decided to get the car hot and try it then. It still said no codes. After my car got hot it decided not to start by sounding just like a dead battery. It tried to start then just clicked. It had done this before then started when it cooled down. This really baffles me do you have any other suggestions?

      donrock
      Don,

      I was a mechanic for many years and in fact have built my own high end street rod. I have also highly modified many of the cars I've owned for racing or just performance purposes. And yea, I've worked on many other's cars as a dealership mechanic in the 1970's.

      As I mentioned in an earlier response the symptoms that you have are classic symptoms of bad battery cable connections, Two cables, two ends on each cable = four points you need to clean and/or tighten.

      This assumes you have a good battery that is holding a charge.

      Question...have you adequately cleaned and tightened those connections?
  • Profile picture of the author Kurt
    Hey Jim...

    Maybe it's the scanner? Can Don remove a fuse or do something simple to force an error code to check the scanner?
    • Profile picture of the author Roaddog
      Originally Posted by Kurt View Post

      Hey Jim...

      Maybe it's the scanner? Can Don remove a fuse or do something simple to force an error code to check the scanner?

      Not a bad idea Kurt...That's why it's next to impossible to diagnose on the net...I have no idea what is or isn't really going on.

      Try what Kurt suggested. (on any sensor fed device)

      If the scanner is lighting up and self testing, it should be good.

      I'm not familiar with what kind of scanner he has.

      There are so many variables these day's (like a computer) that it's much better to do these tests in a very controlled, organized (methodical,,thanks Bill...lol) order.

      Which is far more typing than I can handle...lol
    • Profile picture of the author Bill Farnham
      Originally Posted by Kurt View Post

      Maybe it's the scanner? Can Don remove a fuse or do something simple to force an error code to check the scanner?
      Yea, good idea.

      I've heard if you put the scanner in a paper bag and swing it over your head in a circle all the while singing 'We Won't Get Fooled Again" by the Who you'll immediately find out if the paper bag has any defects in it.

      I'm sorry, I going to give myself an infraction for "Levity Unbecoming".

      On a serious note, you need to eliminate the suspected causes in a methodical manner and then procced in sequence.

      If the cables check out then you procced to the starter/solinoid mechanism.

      But first things first.
  • Profile picture of the author donrock
    This morning the Taurus started right up like nothing was wrong. I guess I'm going to have to follow the advice many of gave me and take it to a mechanic. At least with all the advice I have a few things for the mechanic to check out. Thanks to everyone for contributing to this discussion.
    donrock
  • Profile picture of the author sylviad
    This is going back some years to my husband's 'engine rebuild' days, but I seem to recall this having something to do with the solenoid valve not working when it's hot. According to Wikipedia...

    A solenoid valve is an electromechanical valve for use with liquid or gas. The valve is controlled by an electric current through a solenoid: in the case of a two-port valve the flow is switched on or off; in the case of a three-port valve, the outflow is switched between the two outlet ports. Multiple solenoid valves can be placed together on a manifold. Solenoid valves are the most frequently used control elements in fluidics. Their tasks are to shut off, release, dose, distribute or mix fluids.... A solenoid valve has two main parts: the solenoid and the valve. The solenoid converts electrical energy into mechanical energy which, in turn, opens or closes the valve mechanically.
    Solenoid valve - Wikipedia, the free encyclopedia

    Way back in the 70s, this solenoid valve was a frequent issue with our old cars.

    I remember one very well - I believe it was either my Chevette or Ventura. As soon as it got hot, it would stop. If I waited 15-30 minutes until it cooled, it would start again. Until one day, it just gave out. One day I'd driven from work (about 25 minutes), pulled into the store and shut it off. When I came back 5 min. later, it wouldn't start. I just had to wait.

    Interestingly, one of the first times it happened, I called a mechanic and he couldn't find anything wrong, because by the time he arrived, the car had cooled and it started right up.

    Sylvia

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