LOST JEEPS :: View topic - 2009 Liberty random hot start problem.

Lfh had a great band aid solution. Seems like its a vapor lock issue. Happens when the engine is hot. Really the only sure "fix" I know of when this happens is let it crank for a second, stop, then turn it over again. Fires right up after pushing that vapor to the cats. Just explain to your clients that it's a Jeep thing. Which is 100% true. Haha.

our '010 has been doing that too, for the past 6 months or so.

One note for posters above, fuel injected vehicles with high pressure fuel rails and bypass regulators are immune from vapor lock. Any vapor in the lines would be instantly flushed back to the tank when the key is turned on. I agree it "acts like that" but it's impossible.

Our's is the wife's car, and when this happens she get's worried, PO'd, and talks about trading it in. I got no money to trade it in, have no interest in having a car payment, and less interest in redoing our investment to flat tow the jeep behind our motorhome.

So far, I've replaced the plugs and air filter, and put injector cleaner in the fuel tank.
It's been better but has still happened once or twice.

No codes of course

I have a babied 2012 engine (body not so much) that started this at 30k miles. Not at all electrical issue. Just hot hot fuel. Not at all a concern to whom ever this happens to really. Wouldn't suggest wrapping the exhaust headers at all. Fuel rail rap is better to wrap if you'd want to.

On the KA forum I am a member of, there has not been a correlation to towing or heavy driving (with one exception of a 4.0 owner).

Just a normal short drive, shut down for a short period (Like to run into a store to grab a soda), back out, and no start/long crank to finally get it to start.
The U-tube Vids I have seen of this problem, show the rigs temp gauge sitting dead center.
This is what brought forth my closed loop fueling theory.

However, My above thoughts on closed loop fueling are not correct.
There is no valve which "closes" the fuel supply. Open loop fueling is when the PCM ignores the O2 sensor readings, and runs the rig richer by using a preset injector pulse width.
In order to reach "closed loop" mode; the PCM monitors the O2 sensors, time the rig has been running, operating temp, and ambient air temp. In "closed loop" mode the PCM changes the fuel mixture using the signals from the above to control the pulse width of the injectors to run more fuel efficiently.

However, if the fuel system has a fuel delivery problem (fuel pump, bad check valve, clogged injectors, etc.), or a small vacuum leak, and the rig is attempted to be restarted while still it is in closed loop mode. It would be like trying to start a rig with no choke.

If the bleed back/check valve in the fuel pump does not maintain fuel pressure in the rail. you could get vapor in the lines which then become heat soaked.

I know of 2 KA peeps who did a fuel pump replacement which did solve their issue.
Only 1 peep who did the CAM sensor replacement to fix his. Numerous others have tried replacing the CAM and Crank senors, among other things, to no avail.

I have a request for those with this problem. When this happens, jump out and remove your fuel cap. Then put it back on and try to start it again. Just curious if this may be a back pressure issue.
Another thing to try when this happens.
Jump out and pull the wire plug from the temp sensor and then try to start it.
This will most likely set a code, but will give us more info. Without the temp sensor reading the PCM will revert back to open loop mode.

Front center just between the generator and A/C compressor. Round black plug, 2 wires.

My solution has been to let the fuel pump fully prime before I try and turn the key, instead of starting it instantly.

The other"fix" is when it won't start is to turn the key of and on again right after and it'll turn over.

Occasionally I'll have to give it a little throttle on initial start but she purrs like a kitten after.

jimd118 wrote:

Thank You!

Your welcome. It was kinda hard to get a Pic with my big hands in the way. LOL

TIJKK1220 wrote:

Your case is either a classic check valve failure, or a leaky injector. Either way you are loosing your prime.
I have an old Cherokee I have been doing the "key dance" with for over 10 years now. It always starts after the key dance and a long crank.

It always starts after the key dance and a long crank.

My questions for you guy though is yours doing what happens in that youtube video I posted at the top? It sounds like you guys may just be having a more typically fuel starvation issue from vapor lock where it will just crank and not want to fire up. Mine is doing exactly what happens in that video above where it fires up instantly but just shakes incredibly bad and misses.

Author:	jimd118 [ Fri Mar 31, 2017 1:34 pm ]
Post subject:	2009 Liberty random hot start problem.
Hi Guys, I have a 2009 Liberty that for the last year I have been having a randomly occurring issue when starting. When it acts up it will start and then run incredibly rough to the point of shaking the Jeep notably. It will typically run for 5-10 seconds like this and then quit. It only seems to happen after I have been driving it already, it has never happened on the first start of the day, unsure if its a coincidence or heat related. When it occurs and stalls, it will continue to do it over and over on start attempts for the next 5-10 minutes, and then magically will start up and run fine. Here is a video I found on youtube of a guy having the same exact issue. https://youtu.be/gzPTSQdRYWM I noticed in the youtube comments someone suggested it could be the PCM acting up when hot, any thoughts on that? I took it to a mechanic twice but both times they just didn't know being that I can't reproduce it on the spot. Sometimes it occurs a few times a week than other times it wont happen for a month or two. I recently started a new job in real estate and I am showing lots in a specific mountain community. Its really stressing me out now as I had it happen up on the mountain and to say the least its not a good thing when you have a car load of clients on top of a mountain on a dirt road and they think they are stranded. I start to sweat everytime we get back in the car and I have to start it. I greatly appreciate any help anyone can provide to give me some direction with a mechanic. Thank You!

Author:	lfhoward [ Fri Mar 31, 2017 8:23 pm ]
Post subject:	Re: 2009 Liberty random hot start problem.
I had an XJ once with similar symptoms. If I knew it was only a 5 min stop before I would have to turn the vehicle on again, I would pop the hood and let the heat out. This reduced my successful restart time to a couple of minutes, vs. 10-15 minutes with the hood closed. Also I got heat resistant material and wrapped the injectors and fuel rail with it. This is a band-aid solution that doesn't get to the root of the problem, but you could try it and see if it makes any difference.

Author:	PALiftedKK [ Sat Apr 01, 2017 9:28 am ]
Post subject:	Re: 2009 Liberty random hot start problem.
Lfh had a great band aid solution. Seems like its a vapor lock issue. Happens when the engine is hot. Really the only sure "fix" I know of when this happens is let it crank for a second, stop, then turn it over again. Fires right up after pushing that vapor to the cats. Just explain to your clients that it's a Jeep thing. Which is 100% true. Haha.

Author:	PALiftedKK [ Sat Apr 01, 2017 9:31 am ]
Post subject:	Re: 2009 Liberty random hot start problem.
It also may be to clogged injector nozzles and reduced air flow from the air filter. Filter is self explanatory and the injectors yearly and even monthly need a fuel treatment like lucas. That stuff is really good for the engine and injectors. Best of luck.

Author:	jimd118 [ Sat Apr 01, 2017 10:43 am ]
Post subject:	Re: 2009 Liberty random hot start problem.
PALiftedKK wrote: Lfh had a great band aid solution. Seems like its a vapor lock issue. Happens when the engine is hot. Really the only sure "fix" I know of when this happens is let it crank for a second, stop, then turn it over again. Fires right up after pushing that vapor to the cats. Just explain to your clients that it's a Jeep thing. Which is 100% true. Haha. This was an initial thought but then felt like my experience with engines having vapor lock issues was that they were more predictable. This seems totally random other other than just never occurring on a complete cold start. It can be driven hard up steep mountain dirt roads in the heat with no issue starting after, then randomly I will grab groceries and come out and it wont start. I guess thats what made me think it was something more on the electrical side. Also cars ive had with hot start issues vapor locking will typically have episodes where they just crank for a few seconds due to the fuel starvation. Every time this issue happens it fires right away just instantly does what the video shows above, shaking violently. Any thoughts on that?

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Author:	jimragtop [ Sun Apr 02, 2017 8:08 am ]
Post subject:	Re: 2009 Liberty random hot start problem.
our '010 has been doing that too, for the past 6 months or so. One note for posters above, fuel injected vehicles with high pressure fuel rails and bypass regulators are immune from vapor lock. Any vapor in the lines would be instantly flushed back to the tank when the key is turned on. I agree it "acts like that" but it's impossible. Our's is the wife's car, and when this happens she get's worried, PO'd, and talks about trading it in. I got no money to trade it in, have no interest in having a car payment, and less interest in redoing our investment to flat tow the jeep behind our motorhome. So far, I've replaced the plugs and air filter, and put injector cleaner in the fuel tank. It's been better but has still happened once or twice. No codes of course

Author:	jimd118 [ Mon Apr 03, 2017 11:00 am ]
Post subject:	Re: 2009 Liberty random hot start problem.
jimragtop wrote: our '010 has been doing that too, for the past 6 months or so. One note for posters above, fuel injected vehicles with high pressure fuel rails and bypass regulators are immune from vapor lock. Any vapor in the lines would be instantly flushed back to the tank when the key is turned on. I agree it "acts like that" but it's impossible. Our's is the wife's car, and when this happens she get's worried, PO'd, and talks about trading it in. I got no money to trade it in, have no interest in having a car payment, and less interest in redoing our investment to flat tow the jeep behind our motorhome. So far, I've replaced the plugs and air filter, and put injector cleaner in the fuel tank. It's been better but has still happened once or twice. No codes of course Great information, yeah it did not seem like vapor lock to me, only sign of that was just the hot start only issue. Never predictable though and vapor lock on engines that are sensitive to it in my experience has always been at least semi predictable. This shouts electrical to me, thats what made me questions the PCM. Have you tried replacing the PCM?

Author:	PALiftedKK [ Tue Apr 04, 2017 3:05 pm ]
Post subject:	Re: 2009 Liberty random hot start problem.
I have a babied 2012 engine (body not so much) that started this at 30k miles. Not at all electrical issue. Just hot hot fuel. Not at all a concern to whom ever this happens to really. Wouldn't suggest wrapping the exhaust headers at all. Fuel rail rap is better to wrap if you'd want to.

Author:	jimd118 [ Tue Apr 04, 2017 3:10 pm ]
Post subject:	Re: 2009 Liberty random hot start problem.
PALiftedKK wrote: I have a babied 2012 engine (body not so much) that started this at 30k miles. Not at all electrical issue. Just hot hot fuel. Not at all a concern to whom ever this happens to really. Wouldn't suggest wrapping the exhaust headers at all. Fuel rail rap is better to wrap if you'd want to. What about jimragtops comment about the high pressure fuel rail and bypass valve? Any evidence against that claim? Just curious as I have never heard of a vapor lock issue on these or similar engines. It also acts very differnt than any engine I have ever had vapor lock in.

Author:	Scar0 [ Tue Apr 04, 2017 10:54 pm ]
Post subject:	Re: 2009 Liberty random hot start problem.
This is an ongoing problem with the KK and the 3.7 KA. A lot has been tried, but no definitive answer to the issue. Some have had success with a CAM sensor replacement, others have had success with a fuel pump replacement. This problem usually happens when the rig is warm. Usually after a short drive, 15-30 minutes. If the bleed back valve is failing in the fuel pump then there can be air in the system. If the system is in "closed loop" fueling (which occurs when the rig reaches operating temp), then the check valve which allows the fuel to recycle back to the tank will not open. This could trap the air and vapor lock. Other, IE CAM sensor is getting heat soaked. But in theory when the rig is hot it should always happen... I don't have any real answers, just some theories. Maybe others can build on them.

Author:	PALiftedKK [ Tue Apr 04, 2017 11:06 pm ]
Post subject:	Re: 2009 Liberty random hot start problem.
Scar sounds like hes onto the correct solution. I don't know enough about fuel delivery to make any claims on how to fix this issue. But as previous members have stated and my self, this "harsh start" is not of any concern to the 3.7 owners. Just a quirk of the "engine that could". And many that have had this problem also previously from other groups and sites, it seems a lot more prevalent when the engine is under high stress such as towing. Id say 99% of this "vapor lock" issue has been claims from towing a trailer of any weight or heavy off roading.

Author:	Scar0 [ Wed Apr 05, 2017 3:46 am ]
Post subject:	Re: 2009 Liberty random hot start problem.
On the KA forum I am a member of, there has not been a correlation to towing or heavy driving (with one exception of a 4.0 owner). Just a normal short drive, shut down for a short period (Like to run into a store to grab a soda), back out, and no start/long crank to finally get it to start. The U-tube Vids I have seen of this problem, show the rigs temp gauge sitting dead center. This is what brought forth my closed loop fueling theory. However, My above thoughts on closed loop fueling are not correct. There is no valve which "closes" the fuel supply. Open loop fueling is when the PCM ignores the O2 sensor readings, and runs the rig richer by using a preset injector pulse width. In order to reach "closed loop" mode; the PCM monitors the O2 sensors, time the rig has been running, operating temp, and ambient air temp. In "closed loop" mode the PCM changes the fuel mixture using the signals from the above to control the pulse width of the injectors to run more fuel efficiently. However, if the fuel system has a fuel delivery problem (fuel pump, bad check valve, clogged injectors, etc.), or a small vacuum leak, and the rig is attempted to be restarted while still it is in closed loop mode. It would be like trying to start a rig with no choke. If the bleed back/check valve in the fuel pump does not maintain fuel pressure in the rail. you could get vapor in the lines which then become heat soaked. I know of 2 KA peeps who did a fuel pump replacement which did solve their issue. Only 1 peep who did the CAM sensor replacement to fix his. Numerous others have tried replacing the CAM and Crank senors, among other things, to no avail. I have a request for those with this problem. When this happens, jump out and remove your fuel cap. Then put it back on and try to start it again. Just curious if this may be a back pressure issue. Another thing to try when this happens. Jump out and pull the wire plug from the temp sensor and then try to start it. This will most likely set a code, but will give us more info. Without the temp sensor reading the PCM will revert back to open loop mode.

Author:	jimd118 [ Wed Apr 05, 2017 10:01 am ]
Post subject:	Re: 2009 Liberty random hot start problem.
Scar0 wrote: On the KA forum I am a member of, there has not been a correlation to towing or heavy driving (with one exception of a 4.0 owner). Just a normal short drive, shut down for a short period (Like to run into a store to grab a soda), back out, and no start/long crank to finally get it to start. The U-tube Vids I have seen of this problem, show the rigs temp gauge sitting dead center. This is what brought forth my closed loop fueling theory. However, My above thoughts on closed loop fueling are not correct. There is no valve which "closes" the fuel supply. Open loop fueling is when the PCM ignores the O2 sensor readings, and runs the rig richer by using a preset injector pulse width. In order to reach "closed loop" mode; the PCM monitors the O2 sensors, time the rig has been running, operating temp, and ambient air temp. In "closed loop" mode the PCM changes the fuel mixture using the signals from the above to control the pulse width of the injectors to run more fuel efficiently. However, if the fuel system has a fuel delivery problem (fuel pump, bad check valve, clogged injectors, etc.), or a small vacuum leak, and the rig is attempted to be restarted while still it is in closed loop mode. It would be like trying to start a rig with no choke. If the bleed back/check valve in the fuel pump does not maintain fuel pressure in the rail. you could get vapor in the lines which then become heat soaked. I know of 2 KA peeps who did a fuel pump replacement which did solve their issue. Only 1 peep who did the CAM sensor replacement to fix his. Numerous others have tried replacing the CAM and Crank senors, among other things, to no avail. I have a request for those with this problem. When this happens, jump out and remove your fuel cap. Then put it back on and try to start it again. Just curious if this may be a back pressure issue. Another thing to try when this happens. Jump out and pull the wire plug from the temp sensor and then try to start it. This will most likely set a code, but will give us more info. Without the temp sensor reading the PCM will revert back to open loop mode. Some good info, I will try the fuel cap thing if I have the opportunity. Also where exactly is the temp sensor on the engine to unplug? Thanks.

Author:	Scar0 [ Thu Apr 06, 2017 4:27 am ]
Post subject:	Re: 2009 Liberty random hot start problem.
Front center just between the generator and A/C compressor. Round black plug, 2 wires.

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Author:	jimd118 [ Thu Apr 06, 2017 9:27 am ]
Post subject:	Re: 2009 Liberty random hot start problem.
Scar0 wrote: Front center just between the generator and A/C compressor. Round black plug, 2 wires. Thank You!

Author:	TIJKK1220 [ Thu Apr 06, 2017 12:46 pm ]
Post subject:	Re: 2009 Liberty random hot start problem.
My solution has been to let the fuel pump fully prime before I try and turn the key, instead of starting it instantly. The other"fix" is when it won't start is to turn the key of and on again right after and it'll turn over. Occasionally I'll have to give it a little throttle on initial start but she purrs like a kitten after. Sent from my HTC One M9 using Tapatalk

Author:	Scar0 [ Thu Apr 06, 2017 9:44 pm ]
Post subject:	Re: 2009 Liberty random hot start problem.
jimd118 wrote: Thank You! Your welcome. It was kinda hard to get a Pic with my big hands in the way. LOL TIJKK1220 wrote: My solution has been to let the fuel pump fully prime before I try and turn the key, instead of starting it instantly. The other"fix" is when it won't start is to turn the key of and on again right after and it'll turn over. Occasionally I'll have to give it a little throttle on initial start but she purrs like a kitten after. Your case is either a classic check valve failure, or a leaky injector. Either way you are loosing your prime. I have an old Cherokee I have been doing the "key dance" with for over 10 years now. It always starts after the key dance and a long crank.

Author:	jimd118 [ Fri Apr 07, 2017 10:06 am ]
Post subject:	Re: 2009 Liberty random hot start problem.
Scar0 wrote: jimd118 wrote: Thank You! Your welcome. It was kinda hard to get a Pic with my big hands in the way. LOL TIJKK1220 wrote: My solution has been to let the fuel pump fully prime before I try and turn the key, instead of starting it instantly. The other"fix" is when it won't start is to turn the key of and on again right after and it'll turn over. Occasionally I'll have to give it a little throttle on initial start but she purrs like a kitten after. Your case is either a classic check valve failure, or a leaky injector. Either way you are loosing your prime. I have an old Cherokee I have been doing the "key dance" with for over 10 years now. It always starts after the key dance and a long crank. My questions for you guy though is yours doing what happens in that youtube video I posted at the top? It sounds like you guys may just be having a more typically fuel starvation issue from vapor lock where it will just crank and not want to fire up. Mine is doing exactly what happens in that video above where it fires up instantly but just shakes incredibly bad and misses.

Author:	GordnadoCRD [ Fri Apr 07, 2017 1:11 pm ]
Post subject:	Re: 2009 Liberty random hot start problem.
Scar0 wrote: It always starts after the key dance and a long crank. Sometimes a good dance and a long crank are all the misses needs.

Author:	Scar0 [ Sat Apr 08, 2017 2:38 am ]
Post subject:	Re: 2009 Liberty random hot start problem.
jimd118 wrote: My questions for you guy though is yours doing what happens in that youtube video I posted at the top? It sounds like you guys may just be having a more typically fuel starvation issue from vapor lock where it will just crank and not want to fire up. Mine is doing exactly what happens in that video above where it fires up instantly but just shakes incredibly bad and misses. In the Vid it never starts. It tries to fire but does not catch. Notice the RPM never come up to speed. I see the shaking in the Vid, but I believe it is just how the camera was being held against the steering wheel. My rig does not have the problem. Just trying to assist if I can.