2000 XJ hard start when hot or at altitude

I've got a 2000 4.0L XJ that has problems with restarting once its warmed up (note: this problem has slowly grown worse over the last 20K miles). When cold, the engine starts just fine. After the engine is warmed up AND when the weather is warm, 70 degrees +, the engine has a hard time restarting. It will studder upon starting with no power and diffuculty revving (as if its down a cylinder or two). Once it "clears its throat" for about 5-10 seconds (feathering the throttle) it is OK. This makes a trip to the corner store a real annoyance. If the engine sits long enough (15 minutes or more), it will not have the problem. At the end of fall, I took it up the mountains in Colorado. The temperature as 20 degrees at around 12,000 feet. Restarting the engine was problematic every time. Down at 9200 feet, things were as usual.
Usual maintainence has been performed at regular intervals along with a replacement of all the plugs (100K maintenance with nothing funny from one plug to the next), compression/leakdown test, fuel injector cleaner. I am suspecting a leaky injector (or two) at this time that is flooding a cylinder.
I'll take all the help I can get. Thanks for the great forum!

allterrain said:

After the engine is warmed up AND when the weather is warm, 70 degrees +, the engine has a hard time restarting. It will studder upon starting with no power and diffuculty revving (as if its down a cylinder or two). Once it "clears its throat" for about 5-10 seconds (feathering the throttle) it is OK.

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This is a known issue with 2000 XJs - basically, heat soak on the #3 injector causes the problem. It's easy to fix, though; details can be found in this thread. Doesn't really seem to have much do with altitude - more ambient temperature, engine temperature, and how long it's had to cool down after being shut off.

Also, I'd recommend not feathering the throttle while it's doing this - just let it idle out and within a minute or so it'll return to normal. You may notice that when it's doing the temperature gauge reads above 210degF, but the problem goes away once it's back down to normal.

some of your symptoms sounded similar to mine so i wanted to draw your attention to this so you could rule out the ASD relay. When yours won't restart (or start for that matter) do you hear a pulsing sound coming from the fusebox under the hood? Mine wouldn't restart after warm and i would have to feather the throttle to keep it from dying too.
http://www.naxja.org/forum/showthread.php?t=96697&highlight=2000+won't+start
BTW, thank you casm for pointing out the #3 heatsoak. I was not aware of it and look into it on my baby.

Thanks for the help. Now that I know a TSB was issued for the problem I know I can fix it. I'll let you know if there are any issues after the repair.

2000 Sport, 5" lift, custom built brush guard, winch mount, light bar, snorkel, front suspension mods

I’ve seen this problem come up for years.

• It seems as if the #3 fuel injector fix does not always fix the problem.

• It seems as if altitude, in combination with the oxygenated fuel used in many places aggravates the problem.

• It is essentially a form of vapor-lock.
You have to wait 10-60 seconds until fresh/cool fuel can fill the fuel rail.

• There’s a debate about whether the fuel is vaporizing in the injector(s) or the fuel rail, or BOTH.

• The source of the heat is generally accepted as primarily coming from the exhaust manifold and from the head.

I have seen the many attempted fixes, including:
1. Insulating the injectors.
2. Insulating the fuel rail itself with thermostatic tape.
3. Putting a heat shield wrap around the plate that sits between the exhaust manifold and fuel rail.
4. And one of the most ingenious fixes was a guy who ran copper tubing along the fuel rail. He ran the copper tubing thru a 12VDC coolant pump, and then wrapped/coiled the copper tubing around the A/C dryer. The A/C dryer would chill the copper line, and the liquid running through the line would chill the fuel rail. (That seemed like a lot of work, but it was effective)

I’ve tried all but the copper tubing trick – all with limited to no success.

Here’s what I’m going to try this coming summer:
I am going to get a Ceramic tube to wrap around the fuel rail. I will be looking to use Ceramic Sialon. Note: “Sialon is an outstanding thermal shock resistant material.”

It will probably be June before I can get to this, but I will post my results.

Note: I have a Raytek MT6 Thermometer which should give pretty accurate results.