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Unread 10-16-2012, 01:16 PM   #1
2005WK37David
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NEED HELP. Fuel Rail too hot? WK 3.7

I have a 2005 WK 3.7. For many years I have read this forum for information, but I am currently stumped on something, so I figured I would post. Thanks for all the help in the past.

If the engine is warm, and you shut the vehicle off and restart it within a couple minutes it will run fine.

But if you let the jeep sit for some time with the engine off and the heat from the engine keeps heating the engine compartment, then you try to start it and it will not start, it cranks, it will not start, it sounds very very rough, like it has skipped timing, but it hasnt.

Now if you let it sit for a couple hours so the engine compartment heats up from sitting there, then has time to cool off to ambient temperature again, it will start with no problem.

This problem has plagued me for over a year now. I have pulled codes all the time, I have it set up through a blue tooth adapter and can pull codes and real time info on my android phone.

Thought it could have been a camshaft position sensor or crank sensor, so for $12 each, I replaced them, nothing better over time.

The only conclusion I have come to, is that the heat created in the engine compartment while sitting off with no fan running, is heating the fuel in the fuel rail and causing it to not start with hot fuel.

If it wont start, I pop the hood, put a paper towel or rag over the schrader valve on the fuel rail, and release the hot fuel from the rail, and you can feel that the fuel is extremely hot. Then i go to start it again, and it starts with no issue, other than a lean code, I assume the code is because of the rough start and it wasnt getting fuel.

Has anyone heard of such a thing before? It has taken me some time to narrow this down, but this is the fix for when it wont start when the engine compartment is hot.

I have a wireless thermometer in the engine compartment, and it will be 70 degrees in there while I am driving around, then I park it, and turn it off, and I have seen it climb to 135 degrees, and it will not start.


Last edited by 2005WK37David; 10-16-2012 at 03:03 PM..
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Unread 10-16-2012, 07:33 PM   #2
2005WK37David
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Has anyone had an issue like this?
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Unread 10-16-2012, 08:52 PM   #3
JRLT
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First I heard of it.
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Unread 10-17-2012, 06:55 PM   #4
gotwages
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The only fuel that should be hot would be on your return line but I don't think the 3.7s have a return line, if so this is one of the first gas engines I have ever seen with one. Hot fuel does not change the flash point of the fuel so I don't think it is that. I have never heard of a problem like this and I have been a diesel and gas engine mechanic for nine years.
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Unread 10-17-2012, 07:29 PM   #5
yzjwk
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well it sounds to me like you have a vapour lock problem . Not common in modern fuel injected vehicles , but it does happen .Basically the fuel in the rail heats up enough to start to vaporize because it has stopped moving , the vapor then causes an air lock in the fuel system.The cure , i'm not sure . Do you live at a higher altitude along with what i immagine must be a warmer climate ? You could try a better grade of gas .Has it been happening for a long time ? You may have a blockage in or problem with your purge solenoid . Have you checked for diagnostic codes ?
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Unread 10-17-2012, 09:27 PM   #6
partlowr
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Sounds like a choke related issue since it depends on engine being hot or cold. I am not sure what type of choke these use, but it is most likely an automatic enricher circuit, if this was failing is could lean it out to where it won't start when hot thus the lean code you're getting. Some manufacturers use a vacuum circuit enricher as well. Not sure what type the Jeep 3.7 uses but should be easy to find out.
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Unread 10-18-2012, 12:18 PM   #7
2005WK37David
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I do not see a return fuel line, i looked before and could not locate one.

I believe it is some sort of vapor lock or heat soak issue.

I am in North Carolina foothills, about 1900 feet above sea level.

60 degree days to 108 degree days it will happen.

I do not believe it is a choke issue.

Like I said the fuel rail gets hot from the engine compartment heat (when sitting with engine off after running), then when I expel the fuel out of the rail it will fire right up no issues.

I have tried all grades of gas.

I also use the Lucas fuel additive sometimes.
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Unread 10-18-2012, 12:45 PM   #8
2005WK37David
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I am in the process of trying to run NON ethanol gas and see what that does. Someone said ethanol will boil at a lower temperature than regular gas.

And since E10 gas does not seem to be regulated, it could be that if they are putting too much ethanol in the gas then it is creating issues.
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Unread 10-18-2012, 12:45 PM   #9
yzjwk
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Quote:
Originally Posted by 2005WK37David View Post
I do not see a return fuel line, i looked before and could not locate one.

I believe it is some sort of vapor lock or heat soak issue.

I am in North Carolina foothills, about 1900 feet above sea level.

60 degree days to 108 degree days it will happen.

I do not believe it is a choke issue.

Like I said the fuel rail gets hot from the engine compartment heat (when sitting with engine off after running), then when I expel the fuel out of the rail it will fire right up no issues.

I have tried all grades of gas.

I also use the Lucas fuel additive sometimes.
I would say it definitely sounds like vapor lock . i checked the service manual and unless you have a code to point to a specific part (possibly ambient air temp sensor or asd relay) all i can suggest is test or replace the purge solenoid .If the vehicle is already in a hot or closed loop state , the purge solenoid should activate and it sounds as if it is not for whatever reason . I can't post pictures from my service manual (they are easy to find on-line), but here's the description

SOLENOID-EVAP/PURGE
DESCRIPTION
The duty cycle EVAP canister purge solenoid (2) is
located in the engine compartment attached to a
bracket.
OPERATION
The Powertrain Control Module (PCM) operates the solenoid.
During the cold start warm-up period and the hot start time delay, the PCM does not energize the solenoid. When
de-energized, no vapors are purged. The PCM de-energizes the solenoid during open loop operation.
The engine enters closed loop operation after it reaches a specified temperature and the time delay ends. During
closed loop operation, the PCM energizes and de-energizes the solenoid 5 or 10 times per second, depending upon
operating conditions. The PCM varies the vapor flow rate by changing solenoid pulse width. Pulse width is the
amount of time the solenoid energizes. The PCM adjusts solenoid pulse width based on engine operating condition.
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Unread 10-18-2012, 12:51 PM   #10
2005WK37David
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I have checked for codes, but there are none.

But when it will not start, then it throws a "too lean" code because of it trying to start and it not properly starting.
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Unread 10-18-2012, 01:01 PM   #11
2005WK37David
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I have a 7200+ page pdf file of the service manual also.

Is this where you got that info? If so, what page?

If not I can search through my pdf when I get back to house later tonight.
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Unread 10-18-2012, 01:16 PM   #12
JRLT
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Quote:
Originally Posted by 2005WK37David View Post
I am in the process of trying to run NON ethanol gas and see what that does. Someone said ethanol will boil at a lower temperature than regular gas.

And since E10 gas does not seem to be regulated, it could be that if they are putting too much ethanol in the gas then it is creating issues.
I've never experienced this first hand but there are plenty that I know who swear Ethanol Gas causes vapor lock in their vehicles. Ever since I've had mine, I've only ran non Ethanol 87 Octane and never had an issue like this.
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Unread 10-18-2012, 07:26 PM   #13
yzjwk
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Quote:
Originally Posted by 2005WK37David View Post
I have a 7200+ page pdf file of the service manual also.

Is this where you got that info? If so, what page?

If not I can search through my pdf when I get back to house later tonight.
sorry if i'm too late , but i was looking at ECT/PCM info in section 7-43
and purge solenoid info in section 25-11 .
hope that helps
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Unread 10-18-2012, 07:28 PM   #14
flexyxj
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Quote:
Originally Posted by JRLT View Post
I've never experienced this first hand but there are plenty that I know who swear Ethanol Gas causes vapor lock in their vehicles. Ever since I've had mine, I've only ran non Ethanol 87 Octane and never had an issue like this.
I don't think Ethanol has a thing to do with his starting problem. I've run E30 in mine with no negative results and routinely run E10. I think one the previous posters is right in thinking it has something to do with the purge valve. Poor quality gas will cause similar issues.Whenever I'm in the higher elevations,I always buy the better grade of gas because I've had similar issues with a 4.0 in an XJ.
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Unread 10-25-2012, 04:37 PM   #15
2005WK37David
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Update.

I ran the tank dry and started using only non ethanol gas. And not one issue in the last 1000 miles. Instantly worked better.

After this tank runs out, I will test another ethanol tank of gas.
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