Hey Guys... this one has got me stumped. 5.2 liter motor 4x4 Laramie SLT Shortbox.

Whenever it gets below -5 degree Celsius (approx) - Up here in Ontario - The truck justturnsoverbut doesn't fire.

Battery is new less than 1 year ago. Motor/starter turns over no problem at high revs.

I changed the fuelpumpand lines about a month ago.... Fuel is at the rail when key is on.
Truck runs perfect when warm outside. 4x4 not much use if the truck is on the driveway and won't start.

I am changing sparks, wires cap androtor asap. Had some misfiring and I know plugs are older but not that bad... cause it runs perfect when warmer weather is around. Using Accel coil... 3 years old. As a test I put the stock coil on and surprisingly it started up after a few sputters. But then I put the Accel coil on and since then engine was warm it started up with ease. And it started with Accel coil everytime after that ... but now its cold again and it won't fire. Not sure if there is spark cause I am trying to do this myself and can't turn the motor over and check for spark at same time.

Truck won't fire when cold. Not even a sputter.... but sometimes I get lucky and get a fire or two...then maybe it'll fire up roaring like normal.

If I do get it running and go for a drive sometimes it stalls (Almost likea backfire)when I tromp on the gas from a standstill. But will keep running if I let off the gas early enough.

Has 275,000 km on it... probably needs new timing chain soon... will do in the spring.

Is there anything else that comes to mind I should check?

Frozen gas lines? My tank is full of fresh gas.

Stuck IAC?

Vaccum lines? Don't see anything obvious.

Would coolant issues cause this? or coolant temp sensor?

Have no codes on the PCM.

I can drive it all day i really cold weather as long as I keep using the truck...

then let it sit for a while in the colder temps and then this happens again.

Please give me a hand...this is really trying my patience.....

Thanks.... CRV

 

You say it has fuel at the rail at key-on are you checking with a pressure gauge or just putting a towl over the port and using a screwdriver to crack it open? The reason i ask is because gasoline doesnt freeze at anywhere close to the temps around where you live or any where on earth that i know of lol. But it can thicken up and you say it wants to stall when u stomp it it sounds like the pump cant keep the pressure in the rail when cold. It should have 40-45psi at the test port key on and when running. That is all i can think of i havent had much experience with fuel systems.

 

Gasoline won't even come near "thickening" at the temps he is describing. The flash point ~-97º. Thanks for playing.

 

Yes there is 40 psi at the rail and it's only -5 deg Celsius (23 deg F).... so I agree not much chance of a fuel "thickening" issue.

Starting to think i'ts the IAC from what I've read but not sure. If it's stuck one way it could only start when warm enough and if it's stuck the other it only starts when cold (read from another thread).

It happened to an old Mercedes I had along time ago... very similar symptoms. New IAC fixed it.

Also read from another thread that if the truck dies for no reason... could be IAC... so I'm leaning that way at the moment....

Probably will buy a new IAC for 55 bux and see what happens over the weekend.

Any more ideas anyone????

 

Idea: remove the IAC and hit it with some carb cleaner as well as the IAC hole in the throttle body. Reconnect the IAC but do not bolt it in place. Have a helper turn the key to the 'On' position while you observe the IAC. The plunger should move ~½" or so. If that works, then you are good; otherwise, THEN spring for a new IAC.

 

What weight oil are you running. I have heard alot of people running heavy weight oil in climates that are to cold and having problem starting their vehicles during the winter.

 

If it were mine I would pull the ignition wire from coil to distributor and use a sparkplug tester to see if there was any spark

As far as why the cold does this...perhaps the crankshaft position sensor stops working when the metal shrinks in cold weather because it needs a tight and aligned fit to the notches on the flywheel....or perhaps rotor/cap clearances get too big in the distributor

It is harder for sparkplugs to fire across a big gap in extreme cold.
Smaller sparkplug gaps might help if normal wear over many miles of use has caused your gaps to naturally grow much larger than the original 0.035 to 0.040

A quick check for this might be to blow a hair dryer or electric heat gun into the intake duct

 

I re-read the original post after HankL's post, and IMHO the Accel coil is suspect. The OP states that when the Accel is replaced with an OE coil the truck fires up. I also think there is an issue with the wires, but NOT with the crankshaft sensor *UNLESS* it has dirt/grease buildup on it. I'd pull that and clean it as well.

 

HankL and VWandDodge - you were both a great help!!! Problems solved!!

I changed the wires but no difference,and then the plugs and it fired a little but no start.

Then after reading the Accel coil could bea problem I put the stock one back on and Bingo it fired up.

I was escatic to finally have it running...it's still cold up here....!!


I still had the stall issue during a test run.... and using VWandDodge's previous advice I cleaned then eventually replaced the IAC valve then that was gone too!

This forum is great and now I can enjoy my truck again from behind the wheel rather than under the hood...

Thanks guys.....

 

Sadly, another instance where the Accel coil for the Magnum V8s
failed in service.

Stock coil and MSD coil don't seem to have those failures.