77olds

You have a fundamental misunderstanding of the entire problem, rrich. Maybe it's time you to to do less typing and more reading.

Ok, stop putting words in my mouth. I never said I dno't believe in test equipment - I said that the problem is OBVIOUS to anyone with a brain and common sense, so there's no need - I have diagnosed my issue in other ways that didn't require a fuel pressure gauge.

It IS a problem in warmer climates.

There are not revisions on the TSB from 02 BECAUSE IT CURED THE PROBLEM. The REAL fix would involve replacing the intake and exhaust manifolds with redesigned ones.

No, I didn't claim that at all. The heat comes from the exhaust manifold, which is directly under the intake manifold, which is directly under the injectors, which are almost fully exposed. The TSB even states this as the problem.

AND STOP SAYING GUM WRAPPERS - NOBODY IS TALKING ABOUT GUM WRAPPERS.


I have no idea what you're talking about here. I stated very clearly that this was a TSB, NOT a recall. I WORK AT A DEALERSHIP, I have full access to this information through Alldata, which - SURPRISE - is where we look up TSB information on other manufacturer's vehicles. If you look at the freaking TSB's that have been posted in this thread, you'll see.


rrich, what you are not understanding is that the TSB nails the issue. Checking fuel pressure if a WASTE OF TIME.

Oh no. No. YOU are the one misleading others. We're talking about ONE guy (you) going against CHRYSLER ISSUED TECHNICAL SERVICE BULLETINS and years of experience with this ONE issue, as well as countless first hand accounts of the issue from members of this very forum.


Um, no. If there's vapor in the injectors, it's not magically going to turn back into a liquid at Key On. It still needs to be pushed out of the injectors.

Fuel injectors don't open wide up for a few seconds at a time, you know. They open and close in the blink of an eye. It takes a few seconds for the vapor to be expelled - which falls DIRECTLY in line with the symptoms described in the TSB: "A few seconds of rough idle following a hot soak".


Because fuel injected engines PUSH fuel into the engine as opposed to PULLING it with vacuum like Carburetors.

You mean IN the tank, and they put it there because of the design of the pump - and because liquid gasoline keeps the pump cool. That's why it's bad to run completely out of gas - the pump can overheat trying to pump air.

Same reason they don't put the oxygen sensors 1" after the exhaust port.


Now stop making yourself look silly.

You've displayed an arrogant and ignorant old fashioned point of view that is simply ridiculous. YES, it's wise to consider all possibilities when tackling an issue - but when the fix is something as simple as adding HEAT SHIELDING (I swear if i hear the term gum wrapper one more time...), which SHOULD BE DONE ANYWAY, and that CURES THE PROBLEM, then how can you possibly continue to argue about how it's something else?

If you go to the doctor because your leg hurts and he tells you that it's because you have a knife sticking in it, are you going to argue that he's wrong and it must be broken?

You know, after arguing with you about this subject, I think you probably would.

pmXJ01

I bought some wire and hose insulation that's was rated to 2000 degrees. It was all I could find at the local parts store. Probably not the best "foil gum wrapper" but we'll see if it works. I wrapped all 6 injectors. It supposed to be pretty hot here the next week or two, so I will see what happens.

I read a post where one of you removed the foil shield on top of the intake. Should I do this? It was in pretty bad shape but I left it in there assuming the extra shield would help.

I'll keep the thread updated.

I see a lot of back and forth arguing between a couple of you. Not trying to be rude but all you're doing is cluttering my thread. I appreciate the suggestions and like I said I will work through them all until I find the issue. Please take it to the PM's as it is not contributing much to the actual issue here. Please don't take this the wrong way guys but this isn't high school.

Thanks again for the suggestions and I do appreciate the advice from all who have contributed.

77olds

Insulating the injectors might not help at all - it will only hold the heat in. What you need to do is deflect the heat away, or shield the injectors from the heat.

I apologize for cluttering your thread, but it's an issue that needs to be had out - people giving misinformation. There is no reason why you shouldn't try checking the fuel pressure, as rrich so religiously suggested, BUT he is claiming that the injectors are not the epicenter of the problem, and he is wrong. So by all means, test your fuel pressure. Just don't rule out the fuel vapor in the injectors as the actual problem - as that's what's commonly known to BE the problem, regardless of what rrich thinks.

If I had one of those fancy temperature lasers, I'd love to actually measure the increase in temp of the injectors during a hot soak. That would be interesting to see. I know they get VERY hot. If you've ever pulled old injectors, you can see what the heat does to them - the plastic is very brittle and usually cracked.

Remember - rrich thinks the same heat shield material NASA uses on space shuttles isn't good enough for your Cherokee.

pmXJ01

I don't disagree with you that I think the problem lies within the injectors just like the TSB's say. It is my opinion that insulating the injectors may indeed trap heat in but it should also deflect heat and make it take longer to get in the injectors as well. I figure the material that I used should be very similar to what the TSB is calling for so I'll see if that helps at all.

77olds

It's worth a try. Let us know how it goes!

the buddmang

Rrich - the way you can tell it only affects the #3 and #4 cylinder is when after this happens you get misfire codes for the.........




Hold on....








Wait for it...........







THE NUMBER 3 AND NUMBER 4 CYLINDERS!

P0303 and P0304 are cylinder 3 and cylinder 4 misfire codes, respectively....

the buddmang

And the correction is to install a heat SHEILD.

NOT A WRAP.


the SHEILD is installed between the injectors and intake/exhaust manifolds.

Of course, you wouldnt know this because you STILL havent read the tsb that was posted (in its entirety) a few pages ago....

cactus

hi - my first post
I've been reading this with interested.
i just movd her rfrom Oregom with 3 XJ'S - I'm in Barstow now.
2 of then stsrted with ther het soak problem.
A friend told me to meke heat shields for the injectors.
I used aluminum peices, cut to deflect the heat.

The next day my wife got stuck - had to get it towed.
I tried it around town, parked it - it wouldn't start - checked fuel pressure - pressure was 12 lbs. I could hear it gurgling.
Replaced the regulator - no problem since.
Then to see if the heat shilds helped - I took them off and put thn on my brown XJ.

The red one with the new regulator has been fine since.

The brown one did it again - way out in the desert where it was really hot. I got it going again by throwing water on it.
It's getting a regultor tomorrow.

My green one - no heat shields, no probelem at all.

There is more than one way to skin a cat - you just have to start at the right end.
I've found thast there is no absolutes - there is no one perfecvt solution to anything.

It gets warm here - 118 degrees today.

djb383

What years XJs?

rrich

Budd - if you knew how misfire codes were set you'd know that's not true.

I suggest to read what sets them - and get a decent scanner that you can get into the memory with and see for yourself.
When it running rough from recovery, the misfire codes are usually not the ones misfiring.

There are data links available that can interface with your laptop and you can see things you'd never imagine. Look on EBAY.

Once again, you are making things up.

offroadordnance

There is a method to measure internal temp of the injector with an ohmeter and hood closed. The winding resistance of the injector will increase with temp during heatsoak. An ohmeter can be wired to a spare pigtail fitted to the injector . Monitor resistance and record the peak reading compared to the injectors cold resistance at recorded cold ambient temp. Link attached can have recorded values entered to give injector temp. Temp coefficient of copper is .0039.

http://www.endmemo.com/physics/resistt.php

Also; I'd be very interested to see before and after temps from someone who had added the insulators.

rrich

The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.
A liquid in a vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high-pressure has a higher boiling point than when that liquid is at atmospheric pressure. In other words, the boiling point of a liquid varies depending upon the surrounding environmental pressure. For a given pressure, different liquids boil at different temperatures.-----wikipedia.org/wiki/Boiling_Point

The boiling point / vapor point for Gasoline at sea level pressure is anywhere from 100 - 400 degrees - depending on the additives.

That shows the relationship between temperature and pressure and it's effect on when the liquid turns to vapor. Nothing magical, just physics.

Why do you think the radiator cooling system uses a pressure cap to raise the pressure in the system? Every pound of pressure raises the boiling point (vaporization point) a few degrees. That's not internet lore.

How do you think a cooking pressure pot works?

You can easily see that the pressure makes a huge difference in the temperature where liquid turns to vapor. Obviously the 4.0's are right on the ragged edge of fuel boiling into vapor.
The designers selected a pressure that should be high enough - and is, for most vehicles and situations.

Adding insulation may cover up the problem slightly, but does not address the root problem. The root problem is the pressure should be higher to move it away from the boiling point. That's a problem with the initial design. Many other vehicles avoid that problem with higher rail pressure - 50 lbs is typical.

That's why I SUGGESTED checking fuel pressure - while it's vaporized to see if it's low.

Normally we check the rail pressure while running - it should be approx 31 psi - with vacuum connected to the FPR. Disconnect the vacuum line to the FPR and it should be 8-10 lbs higher.

BUT - if it's running with good vacuum the problem is no longer there! All the vapor has been expelled. That's where the self-styled guru's lose it.

IF IT'S IN THE VAPOR CONDITION IT'S NOT RUNNING AND THERE IS 0 VACUUM! DUH! Static pressure should be 39 to 41 psi!
So the rail pressure you read - ENGINE OFF, KEY ON, WHILE IT'S IN THE HOT SOAK CONDITION AND VAPORIZED should be approximately 39 to 41. If you measure it under those conditions and if it truly is vaporized you'll find it much lower if the FPR or supplied pressure from the pump is weak. The pressure may be OK running, but insufficient to cause the vapor to go back to liquid when first started.

Gum wra - ah candy, - ah tinfo - aluminum foils as shielding from below are only a band-aid.
Notice quite a few new cars use higher fuel pressures. 50 lbs is common. WHY?

Since the 4.0's are so close to having that problem, any slight weakness on the part of the pump or FPR will cause problems. If those components are weak now, they will eventually fail - so you'll replace them anyway. (Is there a TSB about fixing a bad pump with foil? Duct tape? Chewing gum?)

But it seems that some folks would rather temporarily fix it for 80 degrees, but still have the same problem when hotter.

The cracking of the injectors doesn't happen when they are relatively new. It's due to the constant cycling from hot to cold over a long period of time - many many miles, many many hot/cold cycles.

Use a laser thermometer and heat an injector up much higher than it gets on the engine. It will melt long before it cracks. But cycle it hot and cold it will.

Use the laser thermometer to actually measure the temps of the injectors during the heat soak problem. Then turn on the key to get pressure - then wait the same time it takes to “clear up.” You'll see the temp remains the same, but the vapor dissipates and it runs fine. Why?

Now do it again after you've put on the insulation. See of there's a difference. Why not?

Fancy laser thermometer? 39.95 http://www.harborfreight.com/catalog...?q=thermometer

But of course patching things with band-aids and internet lore are preferred over logic, physics, and actual testing.

gary s

101 and humid in Chicago yesterday tied a record.Jeep still running fine with factory fix 2 years later. Does not get any hotter than this here. Can't even remember how much "Gum wrapper" from dealer, lets say it was 10 bucks.Took me what 10 minutes to install? Rrich you have been going on about this way longer than that,seems your padding the bill---

Kalali

You are stating the obvious. None of us here can "fix" the initial (poor) design thus the TSB and the heat shield.
If you have a better idea, please put it on the table.

77olds

rrich, please follow me on this. You're obviously intelligent but you're missing something, otherwise you wouldn't have asked this question.

The injector housings being cracked isn't a result of the heat soak problem, and that's not what I was implying. What I WAS implying is that a cracked injector housing can WORSEN the symptoms, as the inner part of the injector is further exposed to heat as opposed to when they're new, and the plastic is NOT cracked. You are right about why the housings crack, but again that was totally beside the point.

Here's a picture of one of my old injectors. Housing is cracked. Heat soak rough idle was BAD when I ran those old injectors. Put the new ones in and the problem was MUCH less severe, and went away completely when I put on the heat shield.

Injector.jpg?t=1326931104


Ok. Here's why. The fuel in the INJECTORS boils into a vapor. It's not unheard of for residual engine heat to boil fuel - used to happen to some carbureted cars.

Since the injectors are sealed tight until they're commanded open by the computer, that vapor has no where to go. Even under full fuel pressure, that vapor is trapped in there, stuck right inside the injectors, waiting to get out.

When you start your engine and the computer starts opening the injectors, little puffs of that vapor are released - and the cylinders do not fire fully, causing the rough idle.

After a few moments of this, all of the vapor is expelled from the injectors (thanks to fuel pressure), and the engine begins to run normally.

Yes, I DO see a difference. I put a heat shield on and the problem went away. The injectors are not getting nearly as hot as they used to, at least not hot enough to boil the fuel.

As far as your "fancy laser thermometer", here's a picture my co-worker took, using his to measure the temperature inside out shop yesterday:



So. Given the FACT that it's 103 degrees INSIDE the building, and much hotter outside, and my Jeep no longer stumbles after a hot soak,

I'm going to go ahead and say my "gum wrapper" (which is actually a heat shield designed the same way the stuff NASA uses on the space shuttles is) fix actually works because:

A) The Chrysler engineers know what they are talking about
B) This is NOT a new problem and has already been figured out by even the shadiest shade tree mechanic long ago
C) Common sense tells you that if your engine runs normally any other time than immediately following a hot soak then your fuel pump is more than likely doing just fine back there in that nice, cool liquid fuel
D) You can visually see that the design of the intake and exhaust manifolds lends to VERY high temperatures specifically in the injector area of the motor, or
E) All of the Above.

I'm going with E) All of the Above.

Thank you, rrich, for encouraging people to delve a little deeper into problems before just slapping half-cocked solutions onto their vehicles, and I would agree with you that it is definitely a problem when people spout off quick jerry-rig fixes for potentially serious problems, however that is NOT the case in this situation, and unfortunately, you are wrong.

Good day sir.