Will not start when cold?

BUYRITEAUTO21

MEMBER
2007 SUBARU FORESTER
2.5L
4 CYL
4WD
AUTOMATIC
227,000 MILES

I live in a cold climate. My vehicle has to be parked outside overnight. I recently purchased this car. When the temperature is around single digits, it will not start. It turns over like it's going to start, but it never does. I put a jump pack hoping the extra charge would be enough and it wasn't. Once the temperature warms, the car starts like nothing was ever wrong. What would be causing this?

Thanks

4 Replies

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

Hi,

It sounds like it could be a failing engine coolant temperature sensor (ECT). The powertrain control module receives a signal from the sensor which indicates the coolant temperature. The ECM uses this info to determine how rich or lean to make the fuel mixture.

If the sensor is indicating it is 50 degrees F and in reality, it is 5 degrees, the fuel mixture could be too lean for it to start.

Here is what I want you to try when this happens. See if it starts if you use starting fluid. If it does, then we need to check the signal from the ECT to the ECM to determine if it is accurate. If you have a live data scan tool, wait until the temperature gets really low and check the signal from the ECT before starting or trying to start it. The temperature should be very close to the ambient temperature.

If you take a look at pic 1 below, it gives a better description.

Let me know what you find or if you have other questions.

Take care and Happy New Year.

Joe

See pic below.

Image (Click to make bigger)