Skip the auto shop - Our mechanics make house calls

Q: When it's hot out my car won't start, any ideas?

asked by on

On hot days it won't start.

My car has 97000 miles.
My car has an automatic transmission.

A: A couple of things come to mind. I would fi...

A couple of things come to mind. I would first ask these questions: Is this a no crank or a no start? I will address both scenarios below.

A no crank is when the motor doesn't turn when you turn the key. This is a starting issue. Based on your description, I suspect this is what you mean when you say your Volvo 850 won't start. It is very common for heat to cause the starter motor and bad connection problems. Electricity doesn't like heat. Heat creates high resistance in an electrical circuit. Most commonly this is a starter issue, but other parts of the primary circuit can have bad connections.

Another possibility is similar to your no crank in that it involves and electrical module. Heat plagues all electrical components. The diagnosis of this, however, will first require you or a mechanic to figure out what is missing when and if there is a crank no start. An internal combustion motor needs spark, fuel pressure, cam timing and injector pulse to run. If any of these are missing, you will need to pinpoint why. Once it is known what your car is lacking, only experience will guide you to determine why or what to check for next.

Simply put, if you don't have fuel pressure, you will likely need a fuel pump. If you are missing spark, but have injector pulse, you likely need an ignition module. And that module could be part of the PCM. If you are missing only injector pulse, it could be the PCM. Keep in mind, the first thing I do before diagnosis any of these systems is check all the fuses on the car. If you have all of these, then it is likely a problem with camshaft timing. Checking camshaft timing is an extensive process.

Keep in mind, your failure is only occurring when it is hot. For a mechanic to diagnose your car, you will need to reproduce the problem. Reproducing the problem could be the most challenging part of this diagnosis. If the failure isn't occurring, there is no way to diagnose the intermittent failure, and you should have it checked when the problem occurs. If you need help with all of this, I recommend having a certified technician, such as one from YourMechanic, diagnose your starting issue in order to have the right repairs done.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: No spark, no fuel pump until I jump the starter switch.

The PCM is actually what commands the starter to turn over on this truck, so it is possible that this could be a computer issue. Do you have a check engine light on? If so, have you downloaded any codes?...

Q: Check engine light

This is true, but there are countless other reasons for an illuminated Check Engine Light as well. A loose gas cap will typically set an evaporative emissions (EVAP) system code, such as P0440 or P0455. The EVAP system...

Q: Plug from camshaft position sensor corroded.

Even though you can get the car to start and run by sticking the wires into the connector, it will not keep out moisture and it could corrode even more. I would recommend having a mechanic inspect the sensor and...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...