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  #16  
Old June 21st, 2011, 23:28
Milford Cubicle II's Avatar
Milford Cubicle II Milford Cubicle II is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

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Originally Posted by badron View Post
((((((IMO)))))))))
The real problem is two fold.
First them 2 dam pre cats and the cast iron manifold releasing tons of stored up heat well after key off. This heat generates excessive fuel pressure in the rail, injectors etc.
Holy crap why does everyone seems to think that 00 and 01 XJ's have more than ONE cat???

They just have one, just like every other XJ...

Except Cali emissions packages, those are the only ones that have the precats
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  #17  
Old June 22nd, 2011, 00:03
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DrMoab DrMoab is offline
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Every 01 I've ever seen has the pre cats. I guess every 01 is Cali equipped? Doubt it. Only about half of the 00's ice seen are set up that way.

Btw. FU Kalifornia!
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  #18  
Old June 22nd, 2011, 05:30
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Milford Cubicle II Milford Cubicle II is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

I promise you that it's JUST cali emissions package "equipped" XJ's. I know this because I had to buy a new PCM and found out that there are two part numbers for 00 and 01's, the difference being extra o2 outputs for the cali emissions PCM's. And no, not every 01 is cali equipped - I owned one I'm betting that many of them are though. My 00 isn't "cali equipped" either.

And yes, forget California
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  #19  
Old June 22nd, 2011, 06:46
Redsnake Redsnake is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

My '01 is Cali equipped... and I live in Oklahoma ... :\ I think the dual pre-cats and extra O2 sensors are a d@mn shame. Would love to do away w/them on mine... but that would be an expensive route.
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  #20  
Old June 22nd, 2011, 07:22
anthrax323 anthrax323 is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

There is no doubt that the presence of the pre-catalytic converters is ultimately what triggers this issue, however, I'd rather not focus on that as removing them would violate federal emissions regulations. I also know that hood vents and/or a fan timer would help mitigate the issue, but again, I'm more interested in remedying the root cause of the problem (loss of pressure that allows vapor lock to occur).

So back to the questions at hand...
  1. How long should the injectors hold pressure? I assume indefinitely.
  2. Based on the FSM's description, it sounds as though the check valve is designed to lose pressure as the vehicle cools (as it states it should maintain 30 PSI after 5 minutes). Should a perfectly-functioning check valve hold full pressure for a longer period of time?
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  #21  
Old June 22nd, 2011, 08:50
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Re: Chasing the root cause of heat soak (2001 XJ)

While these are good questions, somebody has to do the testing to find the figures. The actual numbers or times really don't matter, the check valve either works, or it does not. The starting behavior is all the test you need.

If you have starting problems, you most likely need a new Check valve.

My 2000 needs a check valve and starts on the second try. My 99 has a new fuel pump assembly and always starts instantly even after sitting for several weeks.
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  #22  
Old June 22nd, 2011, 09:09
anthrax323 anthrax323 is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

Thanks for the input Tim. In my case, only hot restarts are an issue. Cold starts, even after sitting for a week, are never an issue (first try every time). Does this indicate my check valve is likely okay?
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  #23  
Old June 22nd, 2011, 12:07
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Re: Chasing the root cause of heat soak (2001 XJ)

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Originally Posted by anthrax323 View Post
There is no doubt that the presence of the pre-catalytic converters is ultimately what triggers this issue
Yes, there is doubt. In fact, that's flat out wrong. I've had heat soak issues without the additional cats. IIRC the TSB applies to ALL 00 & 01's regardless of their emissions package. I'm sure the extra cats don't help, but they're not the cause of the issue. The cause is a fuel rail on an iron block and iron head engine with the aluminum intake manifold, that also holds each injector, sitting directly above the exhaust manifold.

Quote:
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Are you referring to that foil mat sitting on top of the intake manifold? If so, I still have that in place.
Yep, that's what I was referring to. It worked well for me.
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  #24  
Old June 22nd, 2011, 17:04
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Re: Chasing the root cause of heat soak (2001 XJ)

Finding the reason for the heat soak is a very good idea. It is the first step to solving an old problem.
Funny thing but my 1996 XJ have that problem and have had that problem for as long as I have it. At this time of the year in South Florida it happens on 1 out of 4 starts if the XJ is sitting less than an hour.
I will continue to monitor this thread for an update.
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  #25  
Old June 22nd, 2011, 17:57
badron badron is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

I had two 01s got them both new in Ohio both had pre cats.
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  #26  
Old June 22nd, 2011, 19:09
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Re: Chasing the root cause of heat soak (2001 XJ)

2001, It was just off of a lease from a New York owner and dealer. I have pre-cats.

Why can I not remove them, and who would know and how?

I have MAJOR heat soak. I plan to replace the plug rail then new injectors and maybe some aluminum foil, hood vents...fan timer...

Last edited by EMSJEEP; June 22nd, 2011 at 19:13.
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  #27  
Old June 22nd, 2011, 20:37
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Re: Chasing the root cause of heat soak (2001 XJ)

Insulate the intake manifold, leave plenty of airflow around the fuel rail, and put a reflector on the bottom of the intake manifold as well. I'm gunna do this soon and I'll let ya know if it helps.
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  #28  
Old June 23rd, 2011, 03:55
anthrax323 anthrax323 is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

Quote:
Originally Posted by EMSJEEP View Post
2001, It was just off of a lease from a New York owner and dealer. I have pre-cats.

Why can I not remove them, and who would know and how?

I have MAJOR heat soak. I plan to replace the plug rail then new injectors and maybe some aluminum foil, hood vents...fan timer...
I've already had a thread on this topic - simply swap the exhaust manifold and engine computer of a non-50 state emissions XJ and you'd be set. Unfortunately, this is illegal at the federal level.

Of the band-aids you described, the fan timer is the one tried-and-true fix I've heard discussed. Hood vents helped some people, but not all.
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  #29  
Old June 23rd, 2011, 06:58
O-Gauge Steamer O-Gauge Steamer is offline
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Re: Chasing the root cause of heat soak (2001 XJ)

The heat soak on mine has been completely eliminated. All it took was to install an electric water pump...

The basic problem is the heat rising off of the exhaust manifold is cooking everything it can get it's pudgy little hands on. The heat must be moved somewhere else. Either run the fan for air cooling or run the water pump for liquid cooling. On my rig, the pump runs for two minutes after shutdown and, if the Heep is at 93C or above, both electric fans run as well. I have zero heat soak issues.
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  #30  
Old June 23rd, 2011, 09:24
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 o-gauge-steamer View Post
The heat soak on mine has been completely eliminated. All it took was to install an electric water pump...

The basic problem is the heat rising off of the exhaust manifold is cooking everything it can get it's pudgy little hands on. The heat must be moved somewhere else. Either run the fan for air cooling or run the water pump for liquid cooling. On my rig, the pump runs for two minutes after shutdown and, if the Heep is at 93C or above, both electric fans run as well. I have zero heat soak issues.
Yeah, both solid solutions that I've considered but again, they're workarounds - I'm after the root cause

Supposedly, the issue is caused by either a failing check valve or leaking injector that leads to enough pressure loss that vapor lock is possible.

Yesterday, I did as scientific a test as I could:
  1. Got the car nice and hot on the way home from work. Highway speeds, AC on, etc.
  2. When I arrived at home, I immediately popped the hood, connected the fuel pressure tester, and closed the hood. Started the car and ran it AC on (idling) for about 5 minutes and shut it off.
  3. I quickly popped the hood and clamped the fuel line connected to the fuel rail, and immediately shut the hood.

Upon doing so, I waited about 15 minutes (right when heat soak is guaranteed under these conditions) and went to check the pressure at the fuel rail... It was steady at 50 psi. At 30 minutes, it had dropped to 28 psi, but I assume this is due to the engine (and really the fuel in the rail) cooling off and pressure going down as a result of this. After an hour, it was below 20 psi.

If the same amount of fuel remains in the fuel rail, what kind of pressure drop can I expect as temperatures drop? Does the result of the above test indicate that my injectors are not leaking? I guess I just don't know the relationship between gasoline temperature and the resulting pressure it exerts.

*EDIT* (Follow-up thought) I'm going to do basically the same test again today, but without the pressure gauge... Get home, pop the hood, clamp the fuel line, close the hood, and wait 15 minutes... At the 15 minute mark, I'll remove the clamp from the fuel line and start the car to see if the vapor lock/heat soak issue is mitigated. If so, I'll turn my attention to the rest of the fuel system upstream of the fuel rail (i.e. the check valve).

Last edited by anthrax323; June 23rd, 2011 at 09:28.
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