Frigid-Crank But No Start!

[Broosedamoose]

(2007 4X4 4.0 Auto) Every time the temperature drops below 30 degrees my truck won't start! It just cranks and cranks! Any other time it starts just fine! I brought it in but they couldn't find anything wrong. I know it's getting fuel because I can smell it after cranking for a while so it's not getting spark. Anybody have any ideas what it could be? I'm thinking it must be a connection somewhere that only separates when it gets really cold. That could be anywhere though!

 

[55trucker]

If you can smell fuel after cranking with no fire then the engine is flooded, no wonder it won't start. Pull the plugs & take a look at them for fouling, pick up a plug wire tester & one by one plug it into each of the plug wires & clip it to ground, crank the engine & watch for the spark jumping the gap.

 

[rusty ol ranger]

Try holding your foot on the floor while cranking, this should kill the injectors and give you the best chance to get it fired

Try pulling codes.....kinda wonderin if you got a failing coolant sensor.

 

[RonD]

You can unplug and plug back in the 4 wire connector on coil pack
And unplug and plug back in the Engine 30+ wire connector, big square one
This cleans the pins and slots, but unlikely the issue

If you have an OBD2 reader see what engine temp shows when there is a No Start

You can get a Bluetooth OBD2 reader for under $20, like an ELM327, that works with any smart phone, APPs are free

All gasoline engines need to be Choked to cold start, fuel injection can't change that
So fuel injected engines have the computer set the level of Choke based on cold engine temp, based on ECT(engine coolant temp) sensor
You can see what ECT temp is at with OBD2 reader, to see if its correct

Choke means Rich Fuel Mix and high idle
The colder it is the richer the mix needs to be, but if ECT is showing a way colder temp, then it could be flooding the engine as said

You are getting spark, simply because engine does start at other times
And computer would set a code and turn on CEL(check engine light) if it wasn't getting spark feedback from each coil in the coil pack, or if coil pack was disconnected

Yes, hold gas pedal down to the floor and then cranking the engine will dry out a flooded engine, it also warms up the cylinders and spark plugs, so engine can start easier on a cold morning

 

[Broosedamoose]

I just got home and it's been 2 hours since I last tried. I pulled both connector a few times each. I let it crank for about 10 seconds but it wouldn't start. I held the pedal to the floor but it just cranks and cranks until the battery started to die. No CEL light. I have an inexpensive OBD2 tablet but not with me. I will have to grab it tomorrow and check the ECT. Normally it starts right up! No hesitation at all. My remote start usually works ok. It's set to crank for 1.2 seconds and if it doesn't sense the RPM's jump up it quits. It only happens when it's really cold outside. It's 18 degrees now. I swear it's like it's not getting spark. But like you said, it should produce a code and the CEL should come on. The tach bumps up while cranking so I don't think it's the crank sensor but what about the cam sensor? Could it be possible that something internally is separating just enough to cause it to fail in really cold weather? Or even in the PCM for that matter. Just strange it only does it when it gets really cold. And, it will usually fire right up after cranking it for a bit (5-10 sec) but this time the battery is dying from cranking so long!

 

[RonD]

No on the CAM sensor, crank sensor is the main timing sensor, Cam is the higher resolution sensor, spins at 1/2 speed, so is used to fine tune injector timing to intake valve opening timing

You could try Quick Start(ether) it has a lower Vapor point than gasoline, that would tell you if you have spark
You can spray it in power brake booster hose or almost any vacuum port on the upper intake, it will be sucked in

Spark can't ignite gasoline, it can only ignite gasoline Vapor, and the colder it gets the less vapor gasoline has
Which is where Choking comes in
Cylinder needs 30% vapor to fire, if the cold gasoline only has 15% vapor then you need twice as much gasoline added to the engine, 10% then 3 times as much
But its a fine line between enough vapor and too much liquid, so drowned spark plugs/flooded engine result if calculations are off, common issue with carbs in cold weather
So if it doesn't start up right way you are heading to flooded engine

You only crank engine with gas pedal to the floor for maybe 20 seconds to dry it out, then you try to start it normally, again
It can't start with pedal to the floor, no injectors/no fuel to start

Ether has a lower vapor point which is why many use it to start any gasoline(or diesel) engine when its cold out
Handy to have around, in cold weather or warm, to test any engine

 

[Broosedamoose]

I tried starting this morning but same thing. The ECT was reading -9 Celsius (15.8 Fahrenheit) which was correct. I waited about ten minutes and then held the pedal to the floor and cranked it for like 5 seconds just to be sure it wasn't flooded. I used some starting fluid (ether) this time but it still didn't start! It's 36 outside now and when I first tried to start it, she cranked and cranked. I waited about 10 minutes and tried again and it cranked for about 5 seconds and then started. It's like a switch was suddenly turned on! No stumbling of the engine and no smoke from the exhaust. Looks like I will need to take it in and leave it overnight so he can try it in the morning with the scanner on it. I'll post the results when I get them.

 

[RonD]

Did you notice if the CEL went off while cranking with a no start?

CEL goes off when computer sees a timing pulse from the crank sensor, that's the ONLY WAY the computer knows you want to start the engine, start spark and injectors

There is no connection between starter and computer, or ignition switch

 

[Broosedamoose]

Yes, the CEL goes out. Someone said it could be the coil pack. Wouldn't that throw a code though? I hope it's not the PCM! I've already replaced it a couple years ago and it ain't cheap!

 

[RonD]

Coil pack would be a long shot, and yes it would set a code if computer didn't get feedback from all 3 coils

Pour a little luke warm water on it to see if its effected by the cold temp
Coils are usually only effected by hot temps and even then you have 3 coils on the coil pack, engine would fire if 2 were effected, it would start and miss if 1 coil was bad
All 3 failing is an extreme long shot

It does have just one 12volt wire, purple wire, from fuse 44 in engine fuse box, but again, no 12v would set a code

 

[Broosedamoose]

I don't understand why it's not setting a code! I have a bad feeling it's the PCM and that's why. Could be a tiny electrical component or a solder point that's causing it. He is supposed to come pick it up today but in the mean time I am going to bring the PCM in the house and let it warm up and then try it.

 

[Broosedamoose]

Well, Ron D, you were close! Turned out to be the blades were corroded on fuse #44, the 12v feed for the coil! I still don't understand why it didn't set a code. I'm just happy it's not the PCM like I suspected! Thanks for your help!

 

[RonD]

Good work

Yes, that should have set a code, so not sure how that would not, but hopefully that's the issue