My 2000 4.0 V6 4x4 automatic is slow to start in the winter sometimes. The engine will crank but will not fire. To get the truck to start I have to turn the key back to OFF, wait a second, then lightly pump the gas pedal while cranking the engine. Sometimes this takes several tries before she fires. It only does this in the winter though while it’s fairly cold. I’ve never been stranded with it yet, it’s just annoying and I would like to get it fixed if possible and before it does happen. I have had the truck for 2 years and I’ve had this problem both winters. What could be causing this?

 

Welcome to the forum

Just FYI, there is no "gas" pedal on fuel injected engines, its an "air" pedal, it lets in more or less air, it doesn't add gasoline, like a carburetor "gas" pedal did

Gasoline can not be ignited by a spark............................yes the movie guys get that wrong, lol

Only gasoline VAPOR can be ignited by a spark
Gasoline vapor is what you smell.........................when gasoline is warm, when its COLD there is very little gasoline vapor, colder it is the less vapor there is

This is what the CHOKE was for on carbs, it restricted air flow so MORE gasoline was sucked into the engine when its cold

You need about 30% gasoline vapor in a cylinder for it to Fire
So if gasoline is cold and maybe only 15% vapor you need twice as much gasoline to get to 30%

On fuel injected engines the computer uses the ECT(engine coolant temp) sensor to get the temperature of the engine
If its COLD then computer adds more fuel for starting, so it CHOKES the cold engine for startup

I would change your ECT sensor on speculation, may not be accurate for COLDER temps, so not Choking the engine enough

Multiple cranking as makes sense for that
Compression = heat, so when you crank the cold engine it heats up the cold cylinders, which heats up the cold gasoline so it has more vapor
So after a few cranks it will start, its heated up enough

This is what block heaters are for, to keep the cylinders and gasoline in the fuel system warmer, so there is enough vapor for startup

And this is also why Quick Start(ether) works, ether is vapor even at low temps, so a spark can ignite it

Once engine starts gasoline is easily vaporized as it travels in to the hot cylinders