Random MJ Pre-Build and Lift Questions

[kryptronic]

I just got my 1991 MJ back to driver status and now I'm the process of thinking about how I want to build it out.  For pics, check my build thread.  I have a few questions for everyone, and any help is appreciated:

 

(1) Is there a cross-reference somewhere that I am missing that would translate Cruiser54's Renix tips to the later 91-92 HO/Chrysler platform?  I imagine some tips are not applicable and others are, perhaps with modifications. 

 

(2) My MJ feels like it's running a bit hot.  I have yet to go through the cooling system, but was hoping for some info before I get into it.  My temp gauge consistently reads 210 degrees, and once or twice I've seen it go above that by 20-30 degrees then cool right back down.  I am not sure if my electric fan is working, but assume it is based on the last statement.  It's just that the hood is very hot to the touch after running for just a bit.  So hot I can't keep my hand on it for more than about 15 seconds.  The hoses just seem abnormally hot too.  Sometimes I think I smell coolant, but I might just be imagining it.  Is this normal?  It has never overheated since I've owned it.  Coolant levels are good and the radiator looks new as does the water pump.  I see references to converting to open cooling on here.  Is that even applicable to my 91?

 

(3) My fuel pump is making a whining noise at all times while the MJ is running.  I have no idea if this is normal or not.  It's not very loud, faint actually.  I'm not sure if my YJ does this or not, but on that vehicle with the exhaust so close to the fuel tank, the sound could just be drowned out.  Is this normal, or a sign the fuel pump is on the way out?

 

(4) Concerning lift, I am considering either running 31x10.5x15 tires on 15x7 rims, or 32x11.5x15 tires on 15x8 rims.  If I go 31x10.5x15 tires on 15x7 rims, I may use stock jeep rims (turbines), or I may go with Cragar Soft 8s.  If I go with 32x11.5x15 tires on 15x8 rims, those definitely would be Cragar Soft 8s.

 

I intend fully on keeping the front part of my MJ stock, so this means cutting fenders or fender flares is not an option.  A 97 header swap with an offroad bumper is not an option either.  In fact, I have the factory air dam / spoiler up front and I intend on keeping that.  So with all that baggage between the spoiler and fender flares, how much lift will I need if I want absolutely no rub at full stuff with the front sway bar disconnected, without any steering stop adjustment.  I'm OK with bump stopping, if need be.

 

- Lift required and components for 31x10.5x15 tires on 15x7 stock rims - would switch to turbines?

- Lift required and components for 31x10.5x15 tires on 15x7 rims with 4" backspacing?

- Lift required and components for 32x11.5x15 on 15x8 rims with 4" backspacing?

 

I already have 4.10 axles for gearing, and am not afraid to spend money on this.  I would like to do everything lift-wise for reasonable prices, and this does not have to be built for an end-of-the-world scenario (I have my YJ for all that).  But I will spend money.  This lift is mainly for looks, to get up higher in traffic.  I don't want it to ride like crap either.  I put Old Man Emu springs with Hydros, on my YJ for instance.  I want lift and a nice, soft comfortable ride.  Not looking to have my teeth rattled out and like I said, it does not have to be an ultra heavy duty type setup.  This MJ will likely see moderate trails occasionally, mostly on camping trips, and will likely never see rocks or anything extreme.

 

(5) I have the football evap canister under my bumper, and I also have another evap canister for the fuel system.  I'm not sure if I can just re-route everything from the football to the fuel evap can to eliminate the football, or is this is a very bad idea?  Looking to clean up under the hood.  This is a 91.  I'm not sure if earlier models had a evap can for the fuel tank, or if this was introduced witth the HO and the football was a leftover that engineering forgot to delete.  Any info would be helpful.

 

Any input on the above anyone can offer would be greatly appreciated.  Thank you.

[Tex06]

Lot of questions here. I can tell you you'll need more than 4" to clear 32" tires, I'm running stock rims from a 2012 or 2013 Wrangler with roughly 32" diameter tires (whatever came on them and 1.25" spacers) and I scrub in sharp turns. Had 31" before with no issues though. 1992 Pioneer, 4" lift although it may have a little sag to it at this point (ride is good though, used drop brackets for the control arms). Can get you the tire and wheel specs if you like from before, they're in my shed.

 

I also had questions about cooling, my gauge reads 210 normally and climbs as well. I've never heard the aux fan kick on either, although I did test it once to make sure the fan itself was operable (it is). Does anyone know how to test and see if the computer is switching it on at the right time? I've seen temps in the 230+ range while sitting in traffic....I'm halfway through installing A/C and I don't really want to compound an overheating problem in the summertime.

[Minuit]

1. There's really no Cruiser's Tips equivalent for the HO years because for the most part they don't need it. Do you have any specific electrical problems? You can always clean the dipstick tube and fuel pump(behind the LH tail light) ground as a matter of preventative maintenance. I don't remember if you said anything in your build thread but have you checked the fuse box? Any evidence of clutch fluid leakage to the interior should be cause for extreme concern.

 

2. The HO cooling system is a huge improvement over the Renix cooling system and does not need to be modified to work properly. It is an "open" system and is conventional in every way. Don't believe the temp gauge until you've verified it. Believing the gauge's lies has caused many people including myself to "fix" problems that don't exist or not realize problems that really do exist. I would say the hood being hot after a drive is normal especially if your truck didn't have the hood insulation, but "hot to the touch" is different for everyone. My truck runs at a very consistent 205 and and my upper hose feels hot (to my hands, anyway) after driving. Pointing an accurate infrared thermometer on the thermostat housing/upper radiator hose area will tell you all you need to know. You can also backprobe the temperature sensor on the thermostat housing to see what the ECU is reporting the temperature as. It's a thermistor and I can dig up the resistance vs temperature chart if you want. The fan should come on at roughly 220F, but that's ECU temperature and not gauge temperature. If you need to replace the gauge senders, use Mopar senders only! Aftermarket ones are wildly inaccurate - ask me how I know. If you decide to change the thermostat, use the Mopar part only.

 

Side note: you don't necessarily HAVE to backprobe the thermostat housing sensor but I wouldn't recommend unplugging it with the engine running. It throws an instant check engine light and puts the ECU into what I can only describe as "OH $#!&" mode. Probably not great for the oxygen sensor or cat.

 

3. Normal. Mine has made a faint "whuuuuuum" sound for the last 5 years. Aftermarket pumps especially can be very loud. If it starts making a growling noise, worry then.

 

4. I won't muddy the waters here.

 

5. The football isn't an evap canister. It's a vacuum reservoir for the climate control system. You can relocate the football to the engine bay if you so desire, but if you're not experiencing a leak I wouldn't. That adds more clutter to the engine bay, not less. The line going to the football can cause problems sometimes as it's very long.

[Tex06]

Would greatly appreciate the resistance vs temp chart if you can find it!

 

Sent from my SM-G930T using Tapatalk

[HOrnbrod]

Comments in CAPS

 

I just got my 1991 MJ back to driver status and now I'm the process of thinking about how I want to build it out.  For pics, check my build thread.  I have a few questions for everyone, and any help is appreciated:

 

(1) Is there a cross-reference somewhere that I am missing that would translate Cruiser54's Renix tips to the later 91-92 HO/Chrysler platform?  I imagine some tips are not applicable and others are, perhaps with modifications.

 

MOST ALL OF IT IS GREAT FOR RENIX TRUCKS AND USELESS FOR HOs EXCEPT SOME OF THE GROUNDING STUFF. DO ALL THE GROUNDING STEPS THAT DO PERTAIN TO HO's HOWEVER, VERY IMPORTANT.

 

(2) My MJ feels like it's running a bit hot.  I have yet to go through the cooling system, but was hoping for some info before I get into it.  My temp gauge consistently reads 210 degrees, and once or twice I've seen it go above that by 20-30 degrees then cool right back down.  I am not sure if my electric fan is working, but assume it is based on the last statement.  It's just that the hood is very hot to the touch after running for just a bit.  So hot I can't keep my hand on it for more than about 15 seconds.  The hoses just seem abnormally hot too.  Sometimes I think I smell coolant, but I might just be imagining it.  Is this normal?  It has never overheated since I've owned it.  Coolant levels are good and the radiator looks new as does the water pump.  I see references to converting to open cooling on here.  Is that even applicable to my 91?

 

210* IS ABOUT THE NORMAL RUNNING TEMP. THE 91's ARE OPEN COOLING SYSTEMS FROM THE FACTORY. YOUR AUX COOLING FAN SHOULD RUN CONSTANTLY WHEN THE A/C IS ON, AND COME ON WHEN THE COOLANT TEMP GAUGE REACHES ~230. IF IT DOESN'T COME ON TRY REPLACING IT'S COOLANT TEMP SENSOR ON THE THERMOSTAT HOUSING.

 

(3) My fuel pump is making a whining noise at all times while the MJ is running.  I have no idea if this is normal or not.  It's not very loud, faint actually.  I'm not sure if my YJ does this or not, but on that vehicle with the exhaust so close to the fuel tank, the sound could just be drowned out.  Is this normal, or a sign the fuel pump is on the way out?

 

THE BALLAST RESISTOR ON THE LEFT FENDER WELL IS THERE TO SLOW THE FAN DOWN AND PREVENT SOME OF THE NOISE DURING NORMAL OPS. IF IT'S GONE OR BY-PASSED, THE AUX FAN WILL BE LOUDER THAN W/O IT.

 

(4) Concerning lift, I am considering either running 31x10.5x15 tires on 15x7 rims, or 32x11.5x15 tires on 15x8 rims.  If I go 31x10.5x15 tires on 15x7 rims, I may use stock jeep rims (turbines), or I may go with Cragar Soft 8s.  If I go with 32x11.5x15 tires on 15x8 rims, those definitely would be Cragar Soft 8s.

 

I intend fully on keeping the front part of my MJ stock, so this means cutting fenders or fender flares is not an option.  A 97 header swap with an offroad bumper is not an option either.  In fact, I have the factory air dam / spoiler up front and I intend on keeping that.  So with all that baggage between the spoiler and fender flares, how much lift will I need if I want absolutely no rub at full stuff with the front sway bar disconnected, without any steering stop adjustment.  I'm OK with bump stopping, if need be.

 

- Lift required and components for 31x10.5x15 tires on 15x7 stock rims - would switch to turbines?

- Lift required and components for 31x10.5x15 tires on 15x7 rims with 4" backspacing?

- Lift required and components for 32x11.5x15 on 15x8 rims with 4" backspacing?

 

I RUN 31" TIRES ON TURBINE WHEELS. A SET OF NEW MT SPRINGS ON THE REAR AND OME 2"-3" LIFT COILS PROVIDES PLENTY OF CLEARANCE FOR 31's.

 

I already have 4.10 axles for gearing, and am not afraid to spend money on this.  I would like to do everything lift-wise for reasonable prices, and this does not have to be built for an end-of-the-world scenario (I have my YJ for all that).  But I will spend money.  This lift is mainly for looks, to get up higher in traffic.  I don't want it to ride like crap either.  I put Old Man Emu springs with Hydros, on my YJ for instance.  I want lift and a nice, soft comfortable ride.  Not looking to have my teeth rattled out and like I said, it does not have to be an ultra heavy duty type setup.  This MJ will likely see moderate trails occasionally, mostly on camping trips, and will likely never see rocks or anything extreme.

 

CAN'T BEAT OME SHOCKS FRONT AND REAR FOR A SMOOTH RIDE AND GOOD HANDLING.

 

(5) I have the football evap canister under my bumper, and I also have another evap canister for the fuel system.  I'm not sure if I can just re-route everything from the football to the fuel evap can to eliminate the football, or is this is a very bad idea?  Looking to clean up under the hood.  This is a 91.  I'm not sure if earlier models had a evap can for the fuel tank, or if this was introduced witth the HO and the football was a leftover that engineering forgot to delete.  Any info would be helpful.

 

THE VACUUM CANISTER UNDER THE BUMPER IS STRICTLY FOR THE HVAC DEVICES. THE CHARCOAL CANISTER IS P/O THE EMISSIONS SYSTEM. YOU CAN'T COMBINE THEM. EACH NEEDS IT'S OWN DEDICATED VACUUM SOURCE.

 

Any input on the above anyone can offer would be greatly appreciated.  Thank you.

[Minuit]

Would greatly appreciate the resistance vs temp chat if you can find it!

 

Sent from my SM-G930T using Tapatalk

From the '91 electrical manual.

 

°C and °F are mixed up. Guess the editor hadn't had his coffee yet  :rotfl2:

[kryptronic]

Thank you all very much for the input.  Sorry for all the questions in one thread, but I thought that was better than bombing the tech section with multiple posts for each one.

 

It's good to know that the cooling system is already open on HOs.  I had never heard of converting from closed to open before, and now knowing it's a Renix upgrade confirms why I never heard of it.  I appreciate the tips on debugging the cooling as well.  Should either expose an issue or put my mind at ease about it.  The hood does not have insulation on it.  The engine compartment has so much less room in it than a YJ I guess heat build up is a factor of that.  I am going to thoroughly investigate, though.

 

Concerning Cruiser54's Renix tips, that answers why I couldn't find a cross-reference, thank you.  Mostly non-applicable.  I've run through the list to look already to see what's applicable, and will be doing grounds, etc, but most of it was foreign to me coming from strictly an HO background.

 

@Minuit: It is like a hum or whine coming from the fuel pump.  Very faint.  I thought it might be going, but being where it is, it might just be audible.  Anyone else have a faint whining/humming from the fuel tank area?

 

@HOrnbrod: Thanks for the info on that ballast resistor.  I had forgotten to ask about it.  Was wondering what is was doing there.  That, as well as the electric fan are not present on the YJs on which I cut my teeth.  For those turbines on your 2" rear / 3" front lift, with the sway bar disconnected, and at full stuff, do they tuck in under the fenders or do you still have room to go?  Would a rim with about an inch less backspacing rub?

 

@Tex06: The pic you posted is pretty much dead on for what I'm looking for.  Those are D-Window rims, which are very similar to Soft 8s.  Can you confirm what your setup is in that pic?  It looks like 31s with 15x7 rims and 4" of lift, but only you know.  What are the lift components there?

 

I am kind of set on going with aftermarket wheels with 4" backspacing just to push the wheels out a bit further to add to the track width to compensate a little for whatever lift goes on there.  I do like the turbines, though.  And 31s would be nice.  Not sure if I need all that goes with 32s.  The desire is to stay under 4.5" of lift in the front (as that seems to be the make or break the bank mark), with a minimum of 3" of lift in the front and 2" in the rear. I know I can run turbines with no lift and WJ control arms.  I do want some lift, though.

 

Again, much appreciated.

[Pete M]

the aftermarket rims will push the tires out and 32s will then clip the fenders when turning.  31s on stock rims can fit a bone stock truck so they will work great for a 2-3 inch lift.  maybe buy some spacers for the rear so they match the fronts visually.  :thumbsup:  (spacers on the front will do the same thing as aftermarket rims so don't put them there)  See Horbrod's truck for inspiration :D

[Tex06]

4"lift up front, jks shackles in the rear. 31x10.5 r15 tires and American racing rims (unsure of backspacing, can measure later though).

 

Pic of front control arm drop bracket and rear JKS shackle.

 

What I have now that rubs is P255/75R17 Goodyear wranglers on stock 17" wrangler rims with the 1.25" spacer/adapter. And it definitely rubs.

[kryptronic]

4"lift up front, jks shackles in the rear. 31x10.5 r15 tires and American racing rims (unsure of backspacing, can measure later though).

 

This combo produces no rub at full stuff, sway bar disconnected?  It sounds like I need to go up 4" up front, and probably 3" in the back if I want to run 31s on aftermarket rims.  Anybody disagree?  Thanks.

[Jeep Driver]

Stock sagged-out springs with 31s and WJ LCAs.

 

No rubbing of any kind.

 

 

I don't know why people keep saying you have to go up 4" to clear 31s?