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Car Won’t Start When Hot

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Car Won’t Start When Hot

Car Won’t Start When Really Hot Outside/Honda Main Relay

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  • 11 years ago
    Originally Posted by donrockWhen 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 If that doesn’t work clean the cables where they connect at the starter and/or frame.

  • donrock 11 years ago 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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    • 11 years ago 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 They may all have them now, it has been awhile since I bought mine.Invaluable.

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    • I’ll buy you lunch if you ever visit Dan.And if I win you can buy someone a War Room membership.

    Vi Quick Fuel System Check

    This quick fuel system check will help you determine if your engine is starving for fuel. Do this test when the engine is warm and you are having difficulty starting it.

  • First, remove the air cleaner assembly so you have access to the throttle body in your engine. If necessary, consult your vehicle repair manual to identify and remove components.
  • With the engine off, manually open the throttle valve, or have an assistant depress the accelerator pedal to open the valve for you.
  • Spray some starting fluid into the throttle body.
  • Try to start the engine or have an assistant try to start it.
  • If the engine starts for a couple of seconds or seems like it wants to catch, most likely not enough fuel or no fuel is reaching the cylinders. Concentrate on the fuel system: fuel pressure regulator, fuel filter, fuel pump, check valve in the pump assembly, fuel injectors, etc.. Also, check the camshaft and crankshaft sensors, if applicable for your particular model.
  • if the engine is still hard to start, most likely the problem is not in the fuel system.
  • For a more comprehensive help, check the resources at the bottom of this post. These are easy to understand and troubleshoot procedures you can do at home to test components that are bound to give you trouble.

    Worn starter motor brushes can lead to engine starter problems.

    Iv Check For Vapor Lock

    One of the main characteristics of gasoline fuel is its volatility. This is what allows it to mix with air for a good combustion. But allowing fuel to vaporize before it reaches the combustion chamber will create a performance issue called vapor lock.

    Vapor lock may happen when fuel begins to boil on its way to the fuel injection system or carburetor. Under this condition, vapor or bubbles mix with liquid fuel and prevent free flow. Hot weather and fuel lines too close to a hot engine or other hot components will contribute to vapor lock.

    Another cause for vapor lock is clogged vent lines. This line or lines coming from the fuel tank, allow fuel vapor to exit the tank and collect into a charcoal canister. If the vent line clogs or the valve in the line sticks in the close position, vapor will mix with the fuel as it rushes out of the tank, causing engine performance issues.

    Other symptoms of fuel vapor lock may include:

    • no starting
    • Engine line close or touching a hot engine part
    • Clogged vent line
    • Look for any other condition that may overheat the fuel in your particular system

    Fuel vapor lock has practically been eliminated from modern fuel injection systems because of the high pressure under which they operate.

    Still, a worn, or failing check valve or leak in the system may allow air to enter.

    If your vehicle has a carburetor, definitely consider this as a good possibility.

    Sometimes, a faulty fuel pressure regulator can prevent a warm engine from starting.

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    When Cars Won’t Start It’s Often Because Their Engine Oil Has Thickened In The Cold Which Increases Friction And Makes It Harder For The Starter Motor To Spin The Engine

    Why won’t my car start when the engine is hot. Its been 2 months over and over tested that, in the warmed up condition, loose the fuel valve top of the fuel filter, a little gasoline spill, put the ignition key to on position, dont see any more. Just wont start when hot, but will start when cool. Every truly crappy day begins with a car that wont start.

    The most common reason a car wont start is due to a dead car battery or loose car battery terminals. Just wont start when hot, but will start when cool. A car engine would keep on gaining temperature until a while after it was shut off.

    Why is my car hard to start when its hot? The car drives smooth, good responses, idle rpm is stable. Will start up again once engine cools down.

    If wires get hot when you try to start it and the motor is spinning over. The most common causes of overheating include low coolant level , a faulty thermostat, a plugged radiator, a faulty radiator pressure cap, collapsed hoses, non functioning. If the wires are getting hot, but the engine isn’t turning over then the starter.

    Other possible causes of hot start problems. Weve seen it in the movies, weve read it in books, and thats just how it is. Backfires badly due to raw gasoline in the catalytic converter, due to loss of spark in cylinders.

    To check if the problem is a broken starter, look for a clicking noise when you start your vehicle. Why wont my car warm up? Why won’t my car start when the engine is hot.


    Diesel Car Struggles To Start When Hot

    Help! My Car Won

    Diesel engines need to operate with a much higher fuel pressure than petrol engines and as such can suffer from fuel injection problems more often when the engine is hot. A common source of the problem is a failing high-pressure fuel pump. Over time the internal tolerances of the pump can increase, and if hot this can reduce the amount of pressure to below that which is needed by the engine to start.

    There may also be leaks in the fuel lines, especially at the points of connection with the fuel rail and injectors. These can allow air into the fuel system when hot, thus reducing fuel pressure and fuel delivery to the engine cylinder.

    Its also technically harder to start a diesel engine, even when cold due to the higher compression needed to ignite the diesel fuel. If the starter motor or battery is weak then there may not be enough power needed to generate the compression needed to turn over the engine.

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    Reasons Why Your Car Is Sluggish To Start When Its Hot

    If your vehicle is struggling to start again after you have driven it, the most obvious thing to check first is the battery. Modern batteries should be able to restart a car multiple times without being recharged fully. So if you start your car and drive a short distance then you should have no problem restarting it, assuming the battery is in good condition.

    However, most of the time the problem is not with the battery, especially if it is an older, higher mileage vehicle. Some older vehicles can struggle to restart after they have been driven and have warmed up. This problem is usually unique to higher mileage vehicles because, over time, electrical components and wiring can become less capable of operating and carrying electrical current when they are hot.

    Here are a few of the most common reasons why your car is slow to start when it is warm.

    Honda Civic Failing To Start When Hot

    my 2001 honda civic is giving me problem:

    When starting from cold in the morning, the car starts at one click but when driven for a while with the engine at temperature, if I stop and turn off the ignition when I try to start it again it takes a very long time to start.

    When it does start and I drive for a while the car shuts off and the check light come on. I have to leave it for about 5mims for it to start again.

    • 4If the check engine light is coming on, get someone with a code reader to read the fault code and tell you what the code means.Oct 6 ’11 at 14:20
    • This sounds like the problem that old Chevys have. JaimeOct 6 ’11 at 16:11
    • As Timo Geusch pointed out, have it scanned by OBDII scanner. Many auto stores like autozone, o’reilly, etc, do it free. The culprit could be in ignition or fuel injection system. RainDoctorJul 17 ’12 at 20:59
    • You can also pick up one for under $20 on Amazon: . Don’t get ripped off paying $60-200 for one at an auto parts store. But like others have said, if you just want one scan, stores will usually do it for you for free.

    On a first generation Acura Legend , this problem is almost always caused by the main relay being old / stuck. You can smack it , and it’ll start.

    The symptoms you described have 3 common causes on Honda/Acura vehicles.

    Common Causes of your symptom

    In fuel-injected systems, hot-start problems usually indicate that the fuel line is unable to maintain pressure.

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    My Car Is Hard To Start When Warm

    Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology.

    Several faults can cause your car not to start when warm.

    If your car is hard to start when warm, you can trace the issue to one or more several potential faulty components, for example:

    • Clogged air filter
    • Corroded or loose battery terminal or cable
    • Corroded or loose engine ground connection
    • Vapor lock in the fuel system
    • Faulty fuel system
    • Engine control system problems
    • One or more electrical sensors

    Sometimes, diagnosing a hard-to-start warmed engine can take you a few minutes othertimes, it may take some probing around different potential components or systems. To make it easier, the following sections outline the most common sources of trouble and what you can do to check them for potential problems.


    I. Check for a Clogged Air Filter

    II. Check for Corroded or Loose Battery Terminal or Cable

    III. Corroded or Loose Engine Ground Connection

    IV. Check for Vapor Lock

    V. Check for a Leaking Fuel Pressure Regulator or Injector

    VI. Quick Fuel System Check

    VII. Check the Starter Motor and Circuit

    VIII. Troubleshoot the Crankshaft or Camshaft Position Sensor

    IX. Checking for Technical Service Bulletins

    X. Other Potential Problems

    Starter Will Not Crank When Hot

    Car Not Starting when Weather is Hot or Being Driven or Warmed Up / No Crank on Hot Days

    If your starter easily cranks a cold engine, but drags or cranks very slowly when hot, there may be a heat soak problem. Before you condemn the starter as bad, you should perform a system diagnosis of the battery, cables and starter. For a good overview of these tests, visit click on Technical Information, select Training Videos, and view How to troubleshoot a starter problem.

    Assuming that the diagnosis results are within acceptable ranges and the starter cranks fine when cold, it is quite possibly a heat soak condition. What exactly is starter Heat Soak? Without getting into the physics of thermal conduction or Newtons law of convective cooling, it is simply a matter of the starter absorbing and retaining heat from under-hood sources such as the exhaust manifold. This absorbed heat adds resistance to the electrical conductors inside the starter. The additional resistance results in the starter requiring more amperage than it normally does when cool. Once under-hood heat warms the battery, cables, and starter, a tipping point is reached concerning the overall amount of resistance a starter can accept (and still function


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    Make Sure Help Is At Hand

    If your car wont start when youre out and about, you could become stranded. Getting stranded when its particularly hot outside could soon get unpleasant, especially if you havent got much water to drink. Thats why its always a good idea to consider taking out breakdown cover when you buy insurance as a new driver.

    Keep Your Petrol Tank Topped Up

    We all know that an empty petrol tank means a stationary car, but did you also know that starting a cold car first thing in the morning uses 40% more fuel than usual? In other words, if youre heading home from work tomorrow evening and you notice your fuel tank is looking a little low, its a good idea to fill up before you park it up for the night, or you might find yourself caught short the next morning.

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    Symptoms Of Bad Egr Valve

    A stuck open EGR valve can also lead to the buildup of pollutants, dirt from the fuel and create a vacuum leak in the intake manifold, leading to various drivability issues, such as a knocking, rough idle, hard starting, stalling, and even trouble to turn the car over.

    Manually removing and examining the EGR requires some level of technical knowledge and experience. However, you can identify the issue, by looking for these symptoms.

    • Reduction In Power,
    • Stalling

    Test These 3 Things To Get Back On The Road

    8 Common Reason Why Car Won

    It’s easy to get frustrated when you get in your car and the engine won’t turn over. Don’t worry quite yet. If you’re at home, there are three things you can test that will tell you what’s wrongand you might have an inexpensive repair on your hands. The most likely problem is a dead or drained battery. If that’s good, then your battery cables might be dirty or your starter may be going bad. Rule these things out before you spend any time troubleshooting other possibilities.

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    Check Voltage At Battery And Starter Motor

    Take another voltage reading across the battery terminals and compare this to a voltage reading at the starter motor. To get an accurate reading at the starter motor, place one tip of the multimeter on the positive connection on the base of the starter motor and then ground it against the subframe of the vehicle. .

    If the voltage at the starter motor is noticeably lower than at the battery, then there is a problem with the wiring from the battery to the starter motor. This is a common problem with older wiring, and the decrease in conduction gets worse when the wiring is hot.

    What To Do When Your Car Wont Start On A Cold Morning

    The cold dark mornings have crept back into our daily lives and once again, our cars are bearing the brunt of the frosty weather and becoming sluggish as we head deeper into winter.

    What do you do in the morning when your car wont start? You should be on your way to a crucial meeting but youre faced with calling a rescue service, ordering a taxi and making grovelling phone calls to apologise and try to rearrange all your important appointments.

    Its a common occurrence as low temperatures can cause your car battery to produce less current, making it that much harder for your engine to turn over in the morning. The cold can also stop your engine oil from flowing as well as it should, which puts even more strain on the battery. Essentially, cars and cold dont get on well.

    In this guide, we look at the main reasons why cars can struggle to start on cold mornings, offer six practical tips on how to get the engine going, and show you how to prevent non-starters in the future.

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    Other Possible Causes Of Hot Start Problems

    Before you dive in too fast, it’s also possible that the car has more than one thing causing a hard start. You could also have a bad ignition switch, a bad igniter, or a bad ignition coil. To test for spark, you should first perform a simple spark test then you can test the coil itself. Unfortunately, to test the igniter itself, you need an automotive oscilloscopesomething that is used so infrequently that you probably don’t have one in your home shop.

    A malfunctioning main relay will give you the same symptoms as a bad coil or a bad igniter. But the main relay most often fails when the weather is really hot, while the other possible causes will exhibit the symptom nearly all the time. Although you might have a hard start now and then with a faulty main relay, it is usually not enough to cause you much concernyou can usually get the engine started despite the momentary difficulty. But when an igniter or a coil fails, the car won’t start at all until it cools down.

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