Thermostat Question

[Jeepsburg]

Ok,
I have a carburated 89 YJ, and I am in the process right now of switching it over to fuel injection with a Howell kit. I had to replace the exhaust and intake gasket on the head to pass inspection and well I had the engine coolent drained, I was told it might be wise to replace the Thermostat on it (with the engine running, the temerature changes back and forth from 160 -180 degrees). What is the difference in the new set Thermostat degrees (is colder or hotter better?) and also should I run something different now that I will be running fuel injection?

Thanks for your time and comments

P.S. I will try to post how my conversion went and you can ask me question is you have any. I am doing all the work with a friend, and by doing so, I am saving about 2K in labor.

 

[Jeeper99]

Your thermostat won't open to flow water until it reaches that temp rating. If you're like my dad and freeze all the time, go with the 180. The Heater works faster

 

[Jeepsburg]

Is it bad if it keeps changing temp?
What is a good temp for Fuel injection system?

 

[Jeeper99]

Someone else that is more inclined will have better answers, but you may possibly have air in your system causing it to fluctuate?? I have no idea if it matters as far as the fuel injection goes.

 

[xt master]

I have a 1997 tj fuel injected..thermostat is set at 190.

I have not had any problems with.

It will fluctuate when it hits the temp that opens the stat it will start to cycle the coolant threw the radiator to cool the engine,when it hit the low side of the stat it will close and start to reheat..normally in will change around 10 to 20 degrees.

Dont forget if you still have the stock temp sensor it may not be as accurate as you think.

 

[SteelHeadz]

temp change from 160 to 180 back and forth is normal. although 160 is a bit cold..

 

[mud4feet]

.....It will fluctuate when it hits the temp that opens the stat it will start to cycle the coolant threw the radiator to cool the engine,when it hit the low side of the stat it will close and start to reheat..normally in will change around 10 to 20 degrees....

Good answer. It's a thermostat....it will open at it's rated "degree" and as long as your coolant is runing at or above that temperature, it will stay open (basically, all the time after it's warmed up and running). I can't imagine fuel injection having anything to do with thermostat controled operating temperature. If it isn't "redlining", I wouldn't worry about it......as long as it keeps me WARM!!

 

[Vanmantraveler]

Hold the fort here.... You want a nice hot thermostat for all computer controlled motors.... I always use a 190-195 degree thermostat in everything i drive.... unless it calls for a cold thermo....

Reason being.... The Computer keeps the Fuel system in a rich fuel cycle until the motor reaches a preset temp to help warm the motor up. On a nice cold morning You may never reach that preset temp causing the computer never to swap into the normal running mode sucking the fuel down Fast and loading up the O2 and Cat with unburned fuel. Also when the motor is cold all your Piston to cyl wall clearances are tight causing small amounts of wear.... word is warm it up fast to get the motor up to it's designed operating temp.

Just my humble training kicking in here.... I will pile down off my soap box now and go back and sit in the corner.:shades:

 

[Jeepsburg]

Ok, so I guess I will go with a 195 thermostat.
My mech told me I should replace it because it is changing about 20*

Thanks for your replys

 

[ursman]

temp change from 160 to 180 back and forth is normal. although 160 is a bit cold..

X2 from SH. The fluctuation (especially on a early YJ) is perfectly normal. Mine will go from 180 to 200* depending on the engine demands. Noticing that you're in PA, I would say 180* or even a 195* would be just fine. You'll get heat in the cab a little quicker w/ a 160* but you're engine may not get warm enough during the winter cuz the t-stat would be opening too fast. When you install your Howell, you may want to keep your manifold heater in operation. You can either run a relay or just a 12v switch to turn it on during warmup. I don't have mine hooked up so during warmup, it runs a bit rough. Not a big deal though. If you don't see you're temp gauge getting anywhere above 180, then I would say try a 195 and see how it acts.

 

[Jeepsburg]

When you install your Howell, you may want to keep your manifold heater in operation. You can either run a relay or just a 12v switch to turn it on during warmup. I don't have mine hooked up so during warmup, it runs a bit rough.

Just wondering, Do you also have the Howell Fuel Injection kit?

 

[Jeepsburg]

It's FIXED!!
I know it has taken a long time to get here, but I finally finished my Fuel Injection conversion swap.
I still have a few questions thought if someone knows the answer;

1. The instruction mentioned something about the manifold heater needing to be connected (the swap un-connects it), but I was not sure if I should hook it up, and how to go about doing so, if you think it should be done.

2. I am running my ECM off of the 12V switched wire that used to run to my old ECM. Do I need to switch it to a new line or should that work fine.

3. I have two secondary air lines that connect to the catalytic converter, that used to be hooked up to the old carb air cleaner. Can I just let them hang there or do I have to do anything about them.

Thanks so much for anyone who has given me input and though in this process.
If anyone has any questions about the conversion swap, I will be glad to give some input.
It cost $1200 from 4wd.com, but they were very nice and price-matched it down some with another web site.
JT

 

[ursman]

It's FIXED!!
I know it has taken a long time to get here, but I finally finished my Fuel Injection conversion swap.
I still have a few questions thought if someone knows the answer;

1. The instruction mentioned something about the manifold heater needing to be connected (the swap un-connects it), but I was not sure if I should hook it up, and how to go about doing so, if you think it should be done.

2. I am running my ECM off of the 12V switched wire that used to run to my old ECM. Do I need to switch it to a new line or should that work fine.

3. I have two secondary air lines that connect to the catalytic converter, that used to be hooked up to the old carb air cleaner. Can I just let them hang there or do I have to do anything about them.

Thanks so much for anyone who has given me input and though in this process.
If anyone has any questions about the conversion swap, I will be glad to give some input.
It cost $1200 from 4wd.com, but they were very nice and price-matched it down some with another web site.
JT

1. Being that you live in an area that gets pretty cold like me (Denver) it would be advisable to reconnect your manifold heater. This can be done a couple of ways but the easiest would be to run a 12v source to a switch and heater so you can turn it on & off manually. Without the heater connected will just mean that the engine will run richer for longer until it sufficiently warms up. Mine's not hooked up and I haven't had any problems.

2. Running the ECM off the same 12v source is fine. So long as the voltage is present in both crank and run positions and doesn't deviate >.5v. If it does, it will have issues starting and running properly. You should be good though if your previous ECM was hooked up to it.

3. The secondary hoses that your referring to are the AIR pipes and need to be removed completely and taps sealed off. Being that these hoses are connected to the exhaust, they will be putting unneeded hot air into the engine compartment and mess with the back pressure which is pretty critical to the 4.2L to run optimally. I yanked all the smog crap off during the install and screwed in a large bolt into the cat tap. I mashed down the manifold tap w/ BF pliers and welded the seam shut.

You should love the results of your conversion. I did mine early this summer after dealing with vapor lock issuses and fuel starvation everytime I hit a steep. Power is definitely up although since I still have the crappy Peugeot trans, my upper end power is sapped when on the highway, paticuliarly when going up I-70. I'll be swapping in an AX-15 this winter to hopefully remedy that.

 

[Jeepsburg]

1. Being that you live in an area that gets pretty cold like me (Denver) it would be advisable to reconnect your manifold heater. This can be done a couple of ways but the easiest would be to run a 12v source to a switch and heater so you can turn it on & off manually. Without the heater connected will just mean that the engine will run richer for longer until it sufficiently warms up. Mine's not hooked up and I haven't had any problems.

2. Running the ECM off the same 12v source is fine. So long as the voltage is present in both crank and run positions and doesn't deviate >.5v. If it does, it will have issues starting and running properly. You should be good though if your previous ECM was hooked up to it.

3. The secondary hoses that your referring to are the AIR pipes and need to be removed completely and taps sealed off. Being that these hoses are connected to the exhaust, they will be putting unneeded hot air into the engine compartment and mess with the back pressure which is pretty critical to the 4.2L to run optimally. I yanked all the smog crap off during the install and screwed in a large bolt into the cat tap. I mashed down the manifold tap w/ BF pliers and welded the seam shut.

You should love the results of your conversion. I did mine early this summer after dealing with vapor lock issuses and fuel starvation everytime I hit a steep. Power is definitely up although since I still have the crappy Peugeot trans, my upper end power is sapped when on the highway, paticuliarly when going up I-70. I'll be swapping in an AX-15 this winter to hopefully remedy that.

1. Is it bad at all to not have the heater hooked up? If I do hook the heater up to the switched 12v power source, will it always stay on even after it has warmed up? (would that be bad, such as it staying hotter than it really needs to be?) Or should it automatically turn off?

2. There were two "hot" wires, and I used the one for the ECM, and there is still one left over. Also, in the manual, it says to find the blue wire at the relay, but I cannot find any such wire. Do you know which wire it would be, or how to find which is the hot wire?

3. Plugging the two hoses at the far ends would be just as fine, correct? (sorry, I don't have a good welder)

I love the conversion. I feel more HP. I had some problems with the old dieing carburetor, such as poor idle, stalling, a lot of hard starts, flooded very easily, bad warm ups (now it is like ten times better - almost gone - even without the heater), most likely bad gas mileage, and prob a bunch of other things. Yes, power is sapped at highway speeds, but then I got thinking, that the gears were made mainly for off-roading. 8)

Thanks a bunch for replying,

JT

 

[ursman]

If you wanted the man. heater hooked up, you need to run it up to a toggle switch in the cab so that you can turn it on/off manually. Like I said, mine isn't hooked up and I haven't had any problems other than it running a little rough when it's first started. It's not that critical that it be hooked up.

You should only have the couple of wires that go to the new fuse block w/ 3 fuses and the OBD plug port which run to the ECM and one wire to RUN/CRANK source. Below is from the manual:

"Using one of the single weatherpack connectors and terminals supplied, and 16
or 14-gauge wire, connect the ECM fuse block to a 1 2V source that has current
when your ignition key is in BOTH THE CRANK AND RUN positions. (Not an
accessory position, which loses power during cranking). This completes the
electrical harness installation.

CHECKING FOR FULL SYSTEM VOLTAGE- it is not unusual for older Jeeps to experience a battery voltage drop passing through the firewall to fuse block
area. THE GM TBI SYSTEM MUST HAVE FULL BATTERY VOLTAGE TO OPERATE
PROPERLY. Check your voltage to the ECM and compare it with your battery voltage at the battery. If it is more than 1 VOLT less than battery voltage, you will need to correct voltage loss. If this is not possible, run a separate battery power source to the triple fuse block through an ignition controlled relay, or toggle switch on the dash. Low system voltage will result in hard starts and poor idle problems."

It's only necessary to add a relay if you're having the above issue with voltage drop. Otherwise run it and you shouldn't have any other issues.

Finally, plugging the AIR hoses should be fine so long as they're plugged up well. If you're one of those (like me) who love to play in the deep mud or water, you'll fill up the tubes with muck if they're not plugged. Hope this helps!

 

[Jeepsburg]

Haha, your deff right, i did not think of stuff falling into them, I'll plug 'em good
Thanks a bunch, i guess that answers all my questions.
Happy Jeepin'

JT

 

[ursman]

NP anytime. Now get out there an break sumthin! :lol: