After the shutdown cooling

[gary63]

First sorry if someone has posted this already if so move this or point me in the right spot thanks. I know alot of people have talked and done alot to get there xj to run cooler. I'm looking at what I can do to help get the heat out after I shut it down. If I run it at low speed like on a trail or high speed like on the highway it temp. is good. But after if I shut it down and wait for about 5 to8 min. and restart the fuel in the injector #3 has evaporated from the heat and cause a miss fire and ruff idle until gets fuel flowing again.So if I can get the heat away after I shut it down it should be good to go.I was thinking of changing the elec.fan out to one like the older cars had that would keep running after shutdown for a short time. has anyone done that and if so is there any downside for doing this,Becouse I don't see any of the new car using it anymore?Any other suggestion would be helpful I'm not ready to drill holes into the hood yet becouse of water dripping on to hot parts can creat problems cracks or wear on rubber gaskets.Thank for any help.

[4.3LXJ]

Gary, that mod has been done by Muddeprived on this forum, although the write up was not on here. He is an inactive member now, but active again on Cherokee forum XJtalk. Here is his member page so you can contact him on there. I helped him with the wiring to make it work right, but he can direct you to his write up

http://www.cherokeetalk.com/forum/members/muddeprived/

[gary63]

thanks I will keep you up on what I find out and end up doing and if it helps or a wais of time.if I have any quest I will through it out there?We are trying putting vents in the side of the fenders with waterproof fans to see if it will pull air though the front and help to cool things off.

[Carves]

Electric fan to help with trapped engine bay heat after switch off.

Hella makes a relay with a timer ... Not sure on its amps capacity so an additional, high amp relay, may be needed too ??

Electric water pump, on a timer - to reduce actual engine heat causing most of the engine bay heat temps ... expensive little buggers tho.

[gary63]

yes was thinking a timer or a temp. switch so it will run a short time but not to long so it cools the motor to a cold start. A elec. water pump was thinking but I have had them stop working becouse of broken wire blown fuse and other things and the price I'm not happy with. Holes /vents in hood is not off the list it is just around here we have noticed right were the openings are we have noticed were gaskets and rubber parts and metal parts have problems from water dripping sometimes.

[OldFaurt]

First sorry if someone has posted this already if so move this or point me in the right spot thanks. I know alot of people have talked and done alot to get there xj to run cooler. I'm looking at what I can do to help get the heat out after I shut it down. If I run it at low speed like on a trail or high speed like on the highway it temp. is good. But after if I shut it down and wait for about 5 to8 min. and restart the fuel in the injector #3 has evaporated from the heat and cause a miss fire and ruff idle until gets fuel flowing again.So if I can get the heat away after I shut it down it should be good to go.I was thinking of changing the elec.fan out to one like the older cars had that would keep running after shutdown for a short time. has anyone done that and if so is there any downside for doing this,Becouse I don't see any of the new car using it anymore?Any other suggestion would be helpful I'm not ready to drill holes into the hood yet becouse of water dripping on to hot parts can creat problems cracks or wear on rubber gaskets.Thank for any help.

Good evening Gary,
Run on heat is seldom a problem on modern engines unless there are odd circumstances. Running lean, poor coolant flow, etc...
As for the #3 injector evaporating it's fuel, Unless you have a leak in your fuel system, back-flow valve failure, or you have a leaking injector!

That said, I have done a small write up on injector cleaning...
http://www.xjtalk.com/showthread.php?p=177657&highlight=Injectors#post177657
This may help.
If you find the jeep running hot, especially at part throttle conditions (near idle) you may have a vacuum leak, split hose to brake booster, Evap canister, fuel regulator, etc..

Vacuum leaks cause lean fuel mixture as does a faulty fuel pressure regulator, the little blob bolted to the front end of the fuel rail, 1996 and newer has regulator in the pump back in the tank. If the regulator is failing or needing to be cleaned, it can lower pressure to injectors that will cause engine to run lean. The ECU will increase the pulse width (how long injector is on) to compensate, but it can only go so far. Then it goes lean.

So, what you need to do is find out WHAT is causing the heat if there is a heat problem.

Hood vents,
there are a number of guys that have made their own or adapted some from other vehicles that are also very good at heat removal from the under hood area.

Your description of how your jeep runs sounds like low pressure and a leaky #3 injector.

Hope this helps!

[gary63]

All new injectors and good pressure. It dosn't run hot when it is running or idling it is when it is at running temp. and I shut it down and don't wait for it to cool down or start it up after I shut it off (5 to 8 min.) and most of the time it is #3 that miss and jeep put out a wright up on that and they tell you to put a cover over the injector.I have done that it help a little but it still pop up.But thanks on the inf. I will double check everything again and see if I find anything.

[OldFaurt]

All new injectors and good pressure. It dosn't run hot when it is running or idling it is when it is at running temp. and I shut it down and don't wait for it to cool down or start it up after I shut it off (5 to 8 min.) and most of the time it is #3 that miss and jeep put out a wright up on that and they tell you to put a cover over the injector.I have done that it help a little but it still pop up.But thanks on the inf. I will double check everything again and see if I find anything.

If you have a propane torch, Start the engine, then open the valve on the torch but do not lite it and point it at the intake runner / head area for that injector and see if the idle changes a little. Old coot vacuum leak detector trick.
adding the extra fuel (where the air leak might be) will change the engine a bit.
could do it by using a infrared thermometer from harbor freight to see if all the exhaust ports are close to same temp. Good luck Gary! hope you get it worked out!

[gary63]

may try that I have herd of it before we have use carb cleaner and no change wedid the smoke test fulled it with smoke it only came out the tailpipe I have vacuum gage hooked up on it and a fuel pressor gage on it. I did run a infrared thermometer and I even checked it with head camra that was neet but all was good.and Ihave a new coil pack too.

[OldFaurt]

may try that I have herd of it before we have use carb cleaner and no change wedid the smoke test fulled it with smoke it only came out the tailpipe I have vacuum gage hooked up on it and a fuel pressor gage on it. I did run a infrared thermometer and I even checked it with head camra that was neet but all was good.and Ihave a new coil pack too.

Sounds like you have done a great job of it Gary,
I am out of ideas, but will keep looking.
You have covered the situation quite thoroughly.

maybe I should look at mine and do a base line temp on it to see if I can determine how it might be on some but not all.
Thermal camera eh? Gee that must be nice! OK, I am officially jealous!

Weird about the #3 injector! I will watch your progress!
I love learning new things!
Have a great evening!!

[gary63]

I have a 2000 it has a different intake and the exhaust manifold and it traps the heat around the #3 and they came out with a heatcover to keep things from getting cot inbetween the manifolds and starting a fire.

[OldFaurt]

I have a 2000 it has a different intake and the exhaust manifold and it traps the heat around the #3 and they came out with a heatcover to keep things from getting cot inbetween the manifolds and starting a fire.
Oooh, new info!
I did not know that. I will look into that.
Thanks for the update!

[gary63]

the intake was used on earlier xj what years not shour her are some of the year 99, 2000, 2001 the exhaust was changed in 2000 that is why it didn't come with the HP30 it would hit. But I have been told and so far it hasn't crack like the other are known for doing. if that is true I do have a new one on the shelf that I will coat the in and out sides with high temp ceramic paint to help on heat and rust when I change out the motor.

[4.3LXJ]

Oooh, new info!
I did not know that. I will look into that.
Thanks for the update!

Yes, due to emissions requirements in 2000, the intake, exhaust and head were redesigned to meet the new standard. The intake was opened up, the heads restricted and exhaust was probably a little higher temp as a result. The number three injector gets a lot of heat when the engine is turned off momentarily. It cause the gas to vaporize even under pressure. If left to cool, the gas condenses and there is no problem. To avoid a redesign, Chrysler developed a heat shield that went under the base of the injector. It helped, but did not entirely cure the problem. The trick seems to keep air moving under the hood. As I mentioned, Muddeprived who is no longer active on this forum installed a timer to keep the efan running for 5 minutes I think. It was a fancy one and I don't remember the brand, but apparently it worked along with the heat shield. I think also venting the hood is a good thing to too for this purpose

[gary63]

You are right and the vents is on my list but around here I have seen and talk to some people who have the vents in there hoods you have to put them in the right places or you will get rust and cracked parts from the heat and cold water.

[4.3LXJ]

Put them in the front of the hood. That is where they do the most good anyway

[gary63]

up front work good to help get more air going though the radiator and help it run cooler but it also slows the airflow that goes around the back of the motor and though the tunnel around the trans. and t-case. a good trans. cooler helps and the motor coolent running cooler helps but usually the fire wall will start to get hotter and some time the back part of the motor will have proble from the lack of air. the buick v6 the vaives would stick or the gides would go out. So I just check and trying things to see what work and if there is any side affects.