Cold weather troubles

[woodwright]

Having a weird issue. I have a 2000 Silverado with a 5.3. Just recently moved to SW Montana where it gets pretty cold. The last few mornings it's been around 0°f and my truck won't start. Cranks but won't fire. But in the afternoon once it warms up to 20° or so it starts and runs like nothings wrong. No relevant codes when I scanned it. Any ideas? Could this be a VATS issue?

[hatzie]

When the Passlock activates it stalls the engine and some kind of message will show up on the instrument cluster.
Have you checked whether your ignition coils have fire? Injectors activating?

Break out your scope and check the crank position sensor and cam position sensor and wiring when it's acting up.

A scope lets you look at voltage changes over time as a waveform from crank and cam position sensors and the like.
I already have a DSO203 for other work and I'm acclimated to it so I use it. Not the best for automotive work but it's what I have.
If you are just buying a scope to do automotive work I'd invest in an automotive scope rather than a generic unit like my DSO203 for around the same price... The generic units have a steeper learning curve. Not that the automotive variety is super simple but it likely has presets to do some common automotive diagnostic tasks that a generic scope would require actual training or experimentation to setup.

http://www.youtube.com/watch?v=G5xdqTTg6t8

[homemade87]

Originally Posted by woodwright

Having a weird issue. I have a 2000 Silverado with a 5.3. Just recently moved to SW Montana where it gets pretty cold. The last few mornings it's been around 0°f and my truck won't start. Cranks but won't fire. But in the afternoon once it warms up to 20° or so it starts and runs like nothings wrong. No relevant codes when I scanned it. Any ideas? Could this be a VATS issue?

With no codes I would guess the engine is not turning over fast enough in the low temps . What oil weight are you using . May not have the proper oil in it for those temps . Will make the engine turn over slower . The engine has to see a minimum rpm to fire .

Does it sound like the engine dragging slow when cranking ? Battery could be a factor as well at those temps . Or a combo of both .

[woodwright]

It drags a little, but I've had slower starts. Its warmer this week. Probably 35 this morning. It fired right up. I'll check the battery.

[homemade87]

Originally Posted by woodwright

It drags a little, but I've had slower starts. Its warmer this week. Probably 35 this morning. It fired right up. I'll check the battery.

I have seen where a battery will have enough current and turn over an engine but the voltage be down and not crank . The lower voltage will affect the low voltage electronics and not fire .

If battery it will be a easy fix . Let us know how it goes