northwoodsjeepin

this is my first post about my first cherokee, so go easy on me.

I have 99 cherokee classic and live up by lake superior. its been getting down to -20(f) the past couple nights and the jeep won't start. it started fine before the extreme cold hit. when i bought the jeep it had a plug hanging down from the front bumper, i assumed it was a block heater but i'm not sure. when i plug it in a low hum comes from the engine. i brought the battery(690cca) inside overnight and made sure it had a full charge but when i hooked it back up the next day she just cranked and cranked but never started. i have no additives in the gas tank which is about 1/2 full. frozen gas line? what are your thoughts. and is it dangerous to leave it in that cold without starting it?

thanks for your time!

kitsapfreerider

Welcome to the forum!

My XJ has had the same problems the last couple of days with the cold we have been having. First I would check what exactly that plug connects to. It could be a frozen fuel line or a bad CPS. Any check engine lights? Is the starter cranking quick or sluggish? Replace anything recently? Any recent problems other than this?

tjwalker

That plug is almost assuredly for a frost plug heater. Good thing to plug in when it's super cold out! When it's 10 below or colder, I run mine for a couple of hours before starting. Is it absolutely necessary? No; my 99 will start in any weather. But it makes it much easier for the engine to start and it also gives you a headstart on heating the coolant so you get heat faster in the cab! Don't be afraid to use that heater; it costs very little to run it when the weather turns super cold.

When a vehicle cranks fine but doesn't start in cold temps, you must review the condition of your tuneup hardware. If it's been a while, install new Champion copper plugs gapped to .035, quality plug wires, distributor cap and rotor. The importance of fresh tuneup hardware to fast starts cannot be overstated! Secondary ignition components (tuneup stuff) are critical when the engine is being started in close to it's design limitations because of this stupid cold weather we've been having.

Also keeping up with oil change intervals is highly recommended.

If you are using 10% ethanol in your gas and most people in the country are, a frozen gas line isn't your problem. That problem effectively went away with the introduction of ethanol to gasoline.

Good luck and keep us updated!

northwoodsjeepin

its a frost plug heater, no check engine light, my nss is faulty but that doesnt even allow the starter to engage when it acts up. i brought the battery inside the night before and had the heater plugged in, hooked the battery up in the morning cranked quick but never started. brought the battery in again last night and made sure the charge was full. got to 2(f) degrees above zero so i hooked it up again today. also put in the ends of an isoheet bottle in the gas tank that i didnt expect to do much. turned it on, heard the fuel pump engage, started it and 2 seconds later the jeep was running. my guess is combination of thick gas and weak ignition components. what are your thoughts? it was about as cold last night as the night before.

Thanks for your time and input!

tjwalker

If you have 10% ethanol and I'm assuming you do, your gas is not the problem. The alcohol/ethanol concentration in the gas effectively eliminates gas problems in the cold.

I'm still thinking that you have a marginal secondary ignition system (old tuneup parts)

How many miles on plugs, wires, cap, rotor? That stuff is EXTREMELY important to a quick start in very cold weather. Replace them if any question; it's the best money you can spend......

northwoodsjeepin

not sure, bought it from a guy who collected jeeps and bought this one a while back and just let it sit for a while. i think youre right and thats gonna be the next money i put into the jeep

KINGHAAS420

In my experience with my 93 I found it to be the capacitors on the pcm easy way to check is get a hair dryer on low heat blowing at pcm for about 5 to 10 mins with the key in the on position that should heat it up enough for the fuel pump to prime.

investinwaffles

Clean/rebuilt/upgraded injectors helped me significantly in extreme cold starting. Also a 5w oil is ideal (5w40 works great in my XJ @ 170k). Marvel mystery oil also helps in the extreme cold, but it could be in my head, hehe.

Make sure CPS is good, and all electrical connections are clean and tight. Ignition tune up wouldnt hurt either (Plugs are like $1.50 each). Best thing would be to run lots of fresh Shell gas through the system (meaning drive it as much as you can to clean it out).