Cranks but no start below 40° ok 50°+

Greetings.
My son has a 2003 V6 Saturn Vue With kind of a strange issue. ( First let me say it's not Battery/Alt/ Starter related.) When the outdoor Temp is about 40° and below the engine will not start, it just cranks. However if the temp is above let's say 45-50° or more it starts immediately and runs great. I ran a code scan and no codes came up.
Any ideas tips guys?

Thanks so much
Ricvice

 

When it doesn't start, do any of the cylinders fire or is it as if there is no spark on any of the plugs?

Also, how many miles are on those plugs?

First thing i would do is check for spark by pulling the plugs and grounding the electrode to an unpainted chassis surface and observe whether or not a spark is being created. Make sure to pull the fuel injector fuse before starting so that you will not be flooding the cylinders with fuel.

If you have spark, put the plugs back in, put the fuel injector fuse back in, crank the engine a few rotations, then pull a plug and see if it is wet with fuel.

If it is, you have both spark and fuel. Continue on.
I'm assuming you have air and compression as the vehicle runs when the temperatures are warmer.

Looking elsewhere

Check the resistance of the engine coolant temperature sensor. Don't know where it is on this Honda engine but the information is out there. When these sensors fail, they tend to fail open circuit, which the ECM interprets as minus 40°. The ECM then richens the air fuel mix, sometimes to the point that the mixture cannot actually burn. The actual ambient temperature influences the combustion environment. It may be right on the edge of the air temperature at which the very mixture can combust. The S cars had horrible problems with this when those sensors would fail.

If the resistance is above a few thousand ohms or reads infinite, you've likely found your problem. The spec for the resistance is out there too.
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I know this is a Honda engine, but many ECMs of the era would kill spark and fuel if the CKP, crank position sensor, was not sending a signal to the ECM. It's possible that the coil inside the CKP has a break in it and that the circuit becomes discontinuous as a function of temperature. Usually they fail when hot but anything can happen.

This is a starting list of things to check in the order listed. I am by no means able to diagnose what's going on without at least knowing if fuel and spark are present.

Please do those checks, don't forget to put the injector fuse back in, and post back with results.

 

Thank you for your prompt reply , I'll check all of these out and post the results