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  #46  
Old June 25th, 2011, 16:44
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Talyn Talyn is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

Just tell her "its the vtak kickin yo."
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  #47  
Old June 25th, 2011, 18:39
anthrax323 anthrax323 is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

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Originally Posted by Talyn View Post
Just tell her "its the vtak kickin yo."
She's got a 350Z, so at least she'd know enough to laugh at that
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  #48  
Old June 28th, 2011, 09:45
shaman1204 shaman1204 is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

I was chasing a random misfire and had heat soak as well in My 2000 Cali emissions. I replaced the OEM injectors with Mustang 5.0 injectors and never reinstalled the foil guard on the manifold (I thought that was a debris shield anyway?? Not for the heat soak issue?) and have not had a heat soak event since.

I did replaced some other TB sensors as well and it did clear up the misfire. Just stating I have not had the heat soak/hard start since I replaced the injectors. YMMV.
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  #49  
Old June 28th, 2011, 10:17
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Re: Chasing the root cause of heat soak (2001 XJ)

The foil guard is a debris shield. Its to keep dirt from gathering on the hot manifold and starting a fire. The recall is not related to heat soak.
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  #50  
Old June 28th, 2011, 11:41
shaman1204 shaman1204 is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

I thought so, I just thought I read earlier in the thread where people said the debris shield cured their heat soak, but maybe I misread and they meant the injector coozy.
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  #51  
Old March 17th, 2015, 22:17
md21722 md21722 is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

I'm sure there are numerous threads about heat soak. I am not yet interested in work around solution of timers on fans or a timed electric water pump. When my XJ was newer I didn't have any problems. Over time, fuel pump, injectors, pre-cats, have all gotten on in life and the problem exists. Even with the TSB cellulose wrap on injectors #3 and #4.

When I bought my 97 XJ over the summer it had the tell-tale warm start problem. After checking the fuel pressure and believing the fuel injectors to be fine, I replaced the fuel pump and it starts on a dime, every time.

My 01 XJ with 330,000 miles has the original pre-cats, fuel pump, and injectors. Sometimes it takes a few cranks to get going but not as bad as the 97 XJ was before the fuel pump change. Many times it just fires up.

Over time ethanol has been more prevalent in gasoline. I also live at 6,500 ft.

Could fixing this heat soak issue be as simple as replacing the fuel pump assembly?
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  #52  
Old March 17th, 2015, 23:15
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Re: Chasing the root cause of heat soak (2001 XJ)

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Originally Posted by md21722 View Post
I'm sure there are numerous threads about heat soak. I am not yet interested in work around solution of timers on fans or a timed electric water pump. When my XJ was newer I didn't have any problems. Over time, fuel pump, injectors, pre-cats, have all gotten on in life and the problem exists. Even with the TSB cellulose wrap on injectors #3 and #4.

When I bought my 97 XJ over the summer it had the tell-tale warm start problem. After checking the fuel pressure and believing the fuel injectors to be fine, I replaced the fuel pump and it starts on a dime, every time.

My 01 XJ with 330,000 miles has the original pre-cats, fuel pump, and injectors. Sometimes it takes a few cranks to get going but not as bad as the 97 XJ was before the fuel pump change. Many times it just fires up.

Over time ethanol has been more prevalent in gasoline. I also live at 6,500 ft.

Could fixing this heat soak issue be as simple as replacing the fuel pump assembly?
Could be a factor, the fuel turns to vapor (120-160 F.) and/or boils (about the same as water) and at a higher temperature as the pressure rises. If an injector is leaking or a check valve in the pump assembly lets the pressure bleed off quickly, it could allow more vapor in the fuel rail after shutdown and add to the heat soak issue.

I'm not sure about the vapor and boiling point of ethanol blend fuel. Ethanol does have a substantially lower boiling point than gasoline, around 175 F.
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  #53  
Old March 19th, 2015, 11:41
anthrax323 anthrax323 is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

Lots of interesting info in here. Thank you all for the input.

Amazingly, I've solved it. 100%.

What didn't work? Replacing the fuel pump, thinking it was a bad check valve. The issue persisted, no change whatsoever.

What did work? Hard to say which one specifically fixed it, since they were all done at the same time:
  1. New injector O-rings. Most of the injectors rotated with minimal resistance, and the O-rings were dry (and a couple even appeared to be cracking, I believe on #3 and #4). Almost all of them split during the removal process. New O-rings were installed using a thin coating of 75/140 as lube.
  2. Pre-cat delete, replaced with APN header.
  3. Foil/fiberglass debris shield on the intake manifold was damaged while laying on the floor of the garage, and as a result was not reinstalled.

    (Worth noting, but insignificant:)
  4. Valve cover gasket replacement and general engine clean-up (which included new crankcase vents).
I'd really like to see someone do only their injector O-rings and report back whether or not that solves the issue.


I really should've just done the fan timer, but this was far more... fun.
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  #54  
Old March 19th, 2015, 13:26
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Re: Chasing the root cause of heat soak (2001 XJ)

I think its the fact that a lot times the pre cats leak and the bolts are hard to reach and most folks never check the 4 pre cat bolts. A buddy had bad heat soak and he did hood vents and wrapped injectors but later we found the 4 pre cat bolts loose and figured this was the root problem- dumping a ton of hot exhaust ...
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  #55  
Old March 19th, 2015, 13:42
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Re: Chasing the root cause of heat soak (2001 XJ)

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Originally Posted by anthrax323 View Post
I'd really like to see someone do only their injector O-rings and report back whether or not that solves the issue.
It won't.
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  #56  
Old March 19th, 2015, 17:40
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Chasing the root cause of heat soak (2001 XJ)

My guess is the removal of the pre cats fixed it. They create a ton of heat.
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  #57  
Old March 19th, 2015, 18:36
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Re: Chasing the root cause of heat soak (2001 XJ)

Same here. Mine are gone and I don't have heat soak issues, but that isn't the only change
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  #58  
Old September 12th, 2017, 12:17
DPG DPG is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

Resurrecting this one. Hoping for some more insight.

My "00 XJ is having issues. Usually after driving at higher speeds and then slowing down or stopping, it will die. Once that happens, it will not start for at least 15-20 minutes. This has progressively gotten worse over time.

It used to restart quicker and only happen on hot days. Last night it died (around 65 degrees outside) and after 20-25 minutes, I gave up and called a tow truck. Once I got it to it's destination (About 30 minutes later) it fired right up again.

I had just installed the DEI insulation goodies on the fuel rail and injectors, along with the newer 4 hole injectors and O-rings. Same issue. One of my guys thinks it's not the fuel pump, but it sure seems like a good idea to replace it, as it's 18 years old now anyway.

My '00 4.0 liter suffered the cracked head syndrome, so this motor is out of a '99TJ. IIRC, we stayed with the '99 TJ exhaust manifold, but had to do some custom work to mate that to the XJ exhaust. I'll have to look and see if the pre-cat is in there or not. It's not here right now to look at.

Sure sounds to me like I should replace the fuel pump first and possibly remove the pre-cat after that. I don't recall- are there any sensors in the pre-cats? Don't know if I'll have any issues with codes...?

Any updates or insight is appreciated.

Thanks!
Dirk
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  #59  
Old September 12th, 2017, 13:38
N8N_99xj N8N_99xj is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

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Originally Posted by DPG View Post
Sure sounds to me like I should replace the fuel pump first and possibly remove the pre-cat after that. I don't recall- are there any sensors in the pre-cats? Don't know if I'll have any issues with codes...?
Interested as well. I don't have any running issues, but if I forget to crack the hood at a short stop (e.g. getting gas, just running into the store for a few items, etc.) I will vapor lock.

Curious if those *$%^& pre-cats can be deleted in an emissions state where they may not do a visual but definitely will be looking at OBD2.
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  #60  
Old September 12th, 2017, 14:33
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Re: Chasing the root cause of heat soak (2001 XJ)

Have you replaced the CPS and/or checked for spark when it dies?
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