Cold Start Issue - rock to start?

[bcw495]

2000 100 series will not start on cold mornings when left overnight. I’ve got a new powerful battery, starter sounds strong, but vehicle won’t turn over. Somehow found out that if I rock truck or roll truck in neutral across rough ground, it will start and run rich for a bit then everything goes to normal.
I’m currently traveling through extremely remote areas of west texas so hoping to solve the issue in case the rock & roll trick stops working. Any ideas would be great!

 

[Mike NXP]

2000 100 series will not start on cold mornings when left overnight. I’ve got new a powerful battery, starter sounds strong, but vehicle won’t turn over. Somehow found out that if I rock truck or roll truck in neutral across rough ground, it will start and run rich for a bit then everything goes to normal.
I’m currently traveling through extremely remote areas of west texas so hoping to solve the issue in case the rock & roll trick stops working. Any ideas would be great!

What makes you think it runs rich? What happens when you turn the key? Maybe you have some issue with your neutral safety switch based on the rock-n-roll solving the problem?

 

[bcw495]

What makes you think it runs rich? What happens when you turn the key? Maybe you have some issue with your neutral safety switch based on the rock-n-roll solving the problem?

When I turn the key I hear the starter just like normal, for as long as I keep the key held down, it just never turns over.
Thinking it’s running rich from the smell when the motor first gets going, but maybe that’s normal for any cold gas engine. This is my first gas vehicle.
The issue seems cold temperature (30’s) dependent. She starts fine once she’s been run and/or it warms up during the day.

 

[Mike NXP]

When I turn the key I hear the starter just like normal, for as long as I keep the key held down, it just never turns over.
Thinking it’s running rich from the smell when the motor first gets going, but maybe that’s normal for any cold gas engine. This is my first gas vehicle.
The issue seems cold temperature (30’s) dependent. She starts fine once she’s been run and/or it warms up during the day.

Ah , there's a hint. So when the starter is working and you hear the engine trying to start, that's consider "turning over"

Not too many cases of these engines running rich and I would put that lower on the list for now. The rolling back and forth and then it works is kind of strange and makes me wonder if it's a safety switch or key thing but it may just be coincidence


I would call your issue a "Crank no start " which does appear to happen quite often . Some people mess with the EFI relay a bit to help diagnose. I could be way off but when I hear " the engines turning over but not starting " this is my usual advice.

Some light reading material
EFI Relay Bypass Kit (Immobilizer Fix) for UZJ100/LX470 - https://forum.ih8mud.com/threads/efi-relay-bypass-kit-immobilizer-fix-for-uzj100-lx470.952811/



If you're engine is turning over but not starting keep the 4 basics in mind. You need fuel, air, spark, and compression. Chances are air and compression are fine unless you recently overheated or have a rat living in your airbox..... Focus on fuel and spark.....

Fuel delivery could be an EFI relay or pump issue. Spark issues could be from a bad coil but you should be able to get the motor to fire up even with a dead coil. I'm not sure what the neutral safety switch will disable. This thread talks about nuetral safety switch symptoms.


Could also consider basic maintenance stuff like cleaning the MAF and resetting the battery for a fresh start.


Just my guess

 

[bcw495]

Ah , there's a hint. So when the starter is working and you hear the engine trying to start, that's consider "turning over"

Not too many cases of these engines running rich and I would put that lower on the list for now. The rolling back and forth and then it works is kind of strange and makes me wonder if it's a safety switch or key thing but it may just be coincidence


I would call your issue a "Crank no start " which does appear to happen quite often . Some people mess with the EFI relay a bit to help diagnose. I could be way off but when I hear " the engines turning over but not starting " this is my usual advice.

Some light reading material
EFI Relay Bypass Kit (Immobilizer Fix) for UZJ100/LX470 - https://forum.ih8mud.com/threads/efi-relay-bypass-kit-immobilizer-fix-for-uzj100-lx470.952811/



If you're engine is turning over but not starting keep the 4 basics in mind. You need fuel, air, spark, and compression. Chances are air and compression are fine unless you recently overheated or have a rat living in your airbox..... Focus on fuel and spark.....

Fuel delivery could be an EFI relay or pump issue. Spark issues could be from a bad coil but you should be able to get the motor to fire up even with a dead coil. I'm not sure what the neutral safety switch will disable. This thread talks about nuetral safety switch symptoms.


Could also consider basic maintenance stuff like cleaning the MAF and resetting the battery for a fresh start.


Just my guess

Thank you for all this information, hugely helpful, just made it back from the trip.
I cleaned the MAF and even tried starter fluid but on the coldest mornings I just had to wait for temps to warm up above 25 degrees or so for the truck to start.
One morning I made a quick direct wire from the battery to the efi relay, bypassing the fuses, and was able to start the truck.
Looks like a more permanent modification to the EFI wiring will be the solution. Appreciate the help!

 

[Mike NXP]

Thank you for all this information, hugely helpful, just made it back from the trip.
I cleaned the MAF and even tried starter fluid but on the coldest mornings I just had to wait for temps to warm up above 25 degrees or so for the truck to start.
One morning I made a quick direct wire from the battery to the efi relay, bypassing the fuses, and was able to start the truck.
Looks like a more permanent modification to the EFI wiring will be the solution. Appreciate the help!

Glad you made it work.......The EFI bypass kit linked above might useful if that seems to be the problem.

Some may say otherwise but I avoid starter fluid on modern vehicles. Ether is pretty rough stuff... Carb cleaner has the same effect but has some lubricating properties if you must go that route but there really isn't ever a reason to be shooting that stuff into the intake on this motor.