MJ/XJ Specialist Mechanic

[MuchRespect]

Hi everyone,

 

Recently bought a 1990 MJ 4x4 4.0 with 89k original miles, one owner. Been sitting for about 2+ years. Southern California truck.

 

Ran great when I test drove it, just needed starter fluid to start up. Had it inspected before I bought it. Mechanic thought it could be a faulty sensor or possible ECM. So, seller knocked $500 off and I drove it home.

 

After 60 miles, I made it home and it died in my driveway. Clutch cylinder went and the truck wouldn't start. Least I got it home. So, bringing you up to present:

 

-replaced the master cylinder (runs again, needs starter fluid)

-replaced the fuel pressure regulator

-replaced the crank sensor

-replaced the distributor module

-replaced the ECM (this is what got it to start on it's own)

 

In getting in there, I've found it needs a couple of extra things, namely an alternator (no big deal) and the catalytic converter is clogged. I'm having my mechanic tear the cat out and re-weld the exhaust as the smog is current. Down the line I may put a new cat in and try to get it to pass smog legally.

 

If anyone wants to weigh in on anything I've just said or things I should look out for (nearby affected parts, preventative maintenance, etc.), please do. In the meantime, I'd really like to have an expert take a look at this and give it the "real" inspection it clearly needs.

 

CAN ANYONE RECOMMEND A RELIABLE MECHANIC IN THE LOS ANGELES AREA with real knowledge and expertise in XJ/MJ's? I'm hoping to find a specialist. Not looking for a build-out guru, more someone who knows the engine/electrical side of things top to bottom, though if they do it all, that's of course fine, too.

 

Thanks in advance and forgive any unintended noobness in this post.

[Knucklehead97]

Welcome to the forums! 

 

And theres a whole forum here with XJ/Mj specialists who can easily teach you how to become a specialist. They are VERY simple and extremely fun to work on. 3 years ago I knew nothing about working on cars and thanks to this forum I now do it for extra cash on some weekends and can fix almost anything on an MJ without asking questions.

 

Just from what you said, the clogged cat probably is the reason it died. Same thing happened to one of mine the day i got it. It was a whole new truck after I got ridof it. Did you replace the crank sensor with a MOPAR brand one or the Rotto-zone special? Mopar brand is the only one that reliably works. More than worth the extra cash. And plenty of tests you can do on your old crank sensor to help determine IF you evenneeded a new one.

 

2 great tips I have learned over my 3 years

 

1, check all vacuum lines for leaks and get rid of all unnecessary ones or replace hard lines with copper/steel/aluminium tubing.

 

2, diagnose twice, buy parts once.

 

Once again welcome and enjoy ownjng such a fantastic piece of machinery!!!

[MuchRespect]

4 hours ago, Knucklehead97 said:

Welcome to the forums! 

 

And theres a whole forum here with XJ/Mj specialists who can easily teach you how to become a specialist. They are VERY simple and extremely fun to work on. 3 years ago I knew nothing about working on cars and thanks to this forum I now do it for extra cash on some weekends and can fix almost anything on an MJ without asking questions.

 

Just from what you said, the clogged cat probably is the reason it died. Same thing happened to one of mine the day i got it. It was a whole new truck after I got ridof it. Did you replace the crank sensor with a MOPAR brand one or the Rotto-zone special? Mopar brand is the only one that reliably works. More than worth the extra cash. And plenty of tests you can do on your old crank sensor to help determine IF you evenneeded a new one.

 

2 great tips I have learned over my 3 years

 

1, check all vacuum lines for leaks and get rid of all unnecessary ones or replace hard lines with copper/steel/aluminium tubing.

 

2, diagnose twice, buy parts once.

 

Once again welcome and enjoy ownjng such a fantastic piece of machinery!!!

 

Thanks so much for the reply, man! I've got to admit I've been bumming a touch, hoping I didn't make a poor choice with this particular MJ and your words have really lifted my spirits!

My mechanic was the one to replace the crank sensor. I'll find out tomorrow whether it was a MOPAR.

Thanks for the advice on vacuum lines and the general wisdom.

Do you think it's the right move to re-weld the exhaust rather than springing for a replacement cat now? I've read mixed things on rolling without one.

 

Lastly, still learning how to "drive" on this site. You mentioned a "Specialist forum" were you referring to the club in general or is there actually a forum dedicated for noobs asking questions? Haha! What can I say, I'm green af.

 

Thanks again

[MuchRespect]

3 minutes ago, MuchRespect said:

 

Thanks so much for the reply, man! I've got to admit I've been bumming a touch, hoping I didn't make a poor choice with this particular MJ and your words have really lifted my spirits!

My mechanic was the one to replace the crank sensor. I'll find out tomorrow whether it was a MOPAR.

Thanks for the advice on vacuum lines and the general wisdom.

Do you think it's the right move to re-weld the exhaust rather than springing for a replacement cat now? I've read mixed things on rolling without one.

 

Lastly, still learning how to "drive" on this site. You mentioned a "Specialist forum" were you referring to the club in general or is there actually a forum dedicated for noobs asking questions? Haha! What can I say, I'm green af.

 

Thanks again

One last thing I'll add -- when my mechanic replaced the crank sensor (MOPAR tbd) it started up on it's own about 5 times before decided it didn't want to turn over without starter fluid. Not sure if that's valuable intel, but figured I'd toss it in.

[Knucklehead97]

By specialist forum I mean the club in general. You're not going to find a better forum to learn about fixing a specific car or even multiple types of cars. This forum has it all. As far as keeping or getting rid of the cat, I personally got rid of mine. But I live in AL where we don't have smog testing and pretty much no one has a working cat. Whether you get rid of yours or not, if it's clogged then it will make your engine have problems. Including no power. Is it illegal in your state for you to not have an operable cat? If it is, then I would go ahead and replace it with a new one to stay within the law. Did your MJ have any problem starting BEFORE your mechanic replaced the crank sensor? What was his reasoning behind replacing it? 

 

Also in my opinion you got the best year for an MJ. '90 was the only year that always had the good 5-speed (AX-15) instead of the possibility of the weak one (BA10) and had my favorite version of the Inline-6 (the RENIX instead of an HO or "High-Output").

[cruiser54]

welcome.

 

do a fuel pressure test.

 

and, go to www.cruiser54.com and do Tips 1,3,4, and 5. 

[rokinn]

If it sat for 2 years (especially in the hot socal sun) the fuel in the tank is/was very likely bad or at least marginal.  I would change the fuel filter asap and run a can of BG 44k through it and see if this helps.

[MuchRespect]

Thanks, guys. This is already super helpful. The fuel is a great point. Will look at the filter.

 

 

Knucklehead97, In California, you need to pass a state smog test every two years in order to keep your vehicle registered. It passed smog recently so I'm technically okay for a couple of years. If I want it to pass smog when the time comes I'll need to put a new cat in. I may decide to do that before hand depending on how much exhaust I'm breathing in on a daily basis, haha. To answer your other question, yes, the MJ wouldn't start on its own before we tried the crank sensor. It would start with starter fluid and ran well. Then after the 60 miles, I lost the clutch cylinder and the starter didn't want to work at all. Once those were fixed, it was back to running, but not starting without the ether. That's when we tried the crank sensor. Worked great for about five starts and then back to the same issue. That's when we started firing the parts canon at it.

[Knucklehead97]

14 hours ago, cruiser54 said:

welcome.

 

do a fuel pressure test.

 

and, go to www.cruiser54.com and do Tips 1,3,4, and 5. 

Do these and listen to everything this man tells you to do. I would also run without a cat since you've already passed it. Then install one later when funds allow it or it is required to pass again!

[MuchRespect]

Thanks guys, fuel pressure checks out good. Getting into the tips early next week!

[mjeff87]

OP, welcome to the forums.

 

Correlation does not always equal causation.  When you said you replaced the clutch cylinder, did you mean the slave cylinder on (or inside) the transmission, or the actual clutch master on the firewall?  If the slave, that really wouldn't have much to do with the starting system unless you somehow affected the CPS wiring during the work.  But, if you replaced the clutch master......those have a nasty habit of leaking fluid inside the cab, directly down onto the fuseblock.  Brake fluid (what normally is used in the clutch master) is brutal on the plastic fuseblock, the fuses, and all the wiring connectors on the back side of the block.  I'd start by checking the condition of everything in that area.  It's directly above the clutch pedal inside the cab.

 

also, check the wiring to the CPS in the engine compartment for damage.  The wiring runs dangerously close to the exhaust manifold on the back of the engine.  It's possible that the replacement sensors wiring might have gotten melted/damaged somehow.

 

Keep us posted on your progress.....the brain trust here will definitely get it figured out with you

[HOrnbrod]

19 hours ago, mjeff87 said:

also, check the wiring to the CPS in the engine compartment for damage.  The wiring runs dangerously close to the exhaust manifold on the back of the engine.  It's possible that the replacement sensors wiring might have gotten melted/damaged somehow.

 

Agree. And while you are doing that, unplug and clean the CPS harness connector. Doesn't take much corrosion causing resistance on the pins/connectors to knock the CPS signal down, especially on a Renix.

[johnj92131]

On 5/2/2018 at 7:12 PM, Knucklehead97 said:

<snip>     I would also run without a cat since you've already passed it. Then install one later when funds allow it or it is required to pass again!

 

IMHO, above is poor advice to pass the California Smog test.  It is so much easier to pass the test the first time than have to make multiple trips to repair shops and multiple trips to the smog inspection station. 

 

Last time I replaced a CAT, it cost me about $100, that was 4 test cycles ago. 3 cycles ago I failed because of a bad fuel tank cap.  2 cycles ago, I failed because of a cracked exhaust manifold.  This last cycle was the worst and most expensive:  The 8 month old fuel pump started crapping out right on the test dyno.  The car barely ran and I had to tow it to a repair shop.  The shop found low fuel rail pressure and replaced the pump.  Once that was done, I passed the test with no further problems.

 

[Knucklehead97]

9 hours ago, johnj92131 said:

 

IMHO, above is poor advice to pass the California Smog test.  It is so much easier to pass the test the first time than have to make multiple trips to repair shops and multiple trips to the smog inspection station. 

 

Last time I replaced a CAT, it cost me about $100, that was 4 test cycles ago. 3 cycles ago I failed because of a bad fuel tank cap.  2 cycles ago, I failed because of a cracked exhaust manifold.  This last cycle was the worst and most expensive:  The 8 month old fuel pump started crapping out right on the test dyno.  The car barely ran and I had to tow it to a repair shop.  The shop found low fuel rail pressure and replaced the pump.  Once that was done, I passed the test with no further problems.

 

I'm thankful to live somewhere that doesn't have to deal with that, then.

[dmatt5656]

Welcome to the forums! 
 
And theres a whole forum here with XJ/Mj specialists who can easily teach you how to become a specialist. They are VERY simple and extremely fun to work on. 3 years ago I knew nothing about working on cars and thanks to this forum I now do it for extra cash on some weekends and can fix almost anything on an MJ without asking questions.
 
Just from what you said, the clogged cat probably is the reason it died. Same thing happened to one of mine the day i got it. It was a whole new truck after I got ridof it. Did you replace the crank sensor with a MOPAR brand one or the Rotto-zone special? Mopar brand is the only one that reliably works. More than worth the extra cash. And plenty of tests you can do on your old crank sensor to help determine IF you evenneeded a new one.
 
2 great tips I have learned over my 3 years
 
1, check all vacuum lines for leaks and get rid of all unnecessary ones or replace hard lines with copper/steel/aluminium tubing.
 
2, diagnose twice, buy parts once.
 
Once again welcome and enjoy ownjng such a fantastic piece of machinery!!!

I am wanting to get rid of my unnecessary vaccum lines and replace with something a bit more durable. Silicone? I don't know I haven't been able to find anything on this.

Sent from my Z982 using Tapatalk

[Knucklehead97]

13 hours ago, dmatt5656 said:

I am wanting to get rid of my unnecessary vaccum lines and replace with something a bit more durable. Silicone? I don't know I haven't been able to find anything on this.

Sent from my Z982 using Tapatalk
 

I've seen brake lines bent and used and that's what I'm about to be doing to replace the aluminum tubing I used initially. As far as unnecessary vacuum lines, it varies for each state. In Alabama our emission laws are not very strict so it was easy to get rid of a lot of unneeded ones.

[crumbscomanche]

hey just saw this thread. shoot me a message and I'm happy to help out. I've got a garage and have figured out how to do a few things now. I also have a great mechanic on pico and fairfax I can refer you too for anything big. 

[crumbscomanche]

On 5/6/2018 at 8:54 PM, dmatt5656 said:

I am wanting to get rid of my unnecessary vaccum lines and replace with something a bit more durable. Silicone? I don't know I haven't been able to find anything on this.

Sent from my Z982 using Tapatalk
 

@dmatt5656 check my build thread, just put on silicone lines and ran them for 6 hours on the trails in the hot sun with no issue. hpsimotorsports.com 

[ratty]

On 5/1/2018 at 5:01 PM, MuchRespect said:

Hi everyone,

 

Recently bought a 1990 MJ 4x4 4.0 with 89k original miles, one owner. Been sitting for about 2+ years. Southern California truck.

 

Ran great when I test drove it, just needed starter fluid to start up. Had it inspected before I bought it. Mechanic thought it could be a faulty sensor or possible ECM. So, seller knocked $500 off and I drove it home.

 

After 60 miles, I made it home and it died in my driveway. Clutch cylinder went and the truck wouldn't start. Least I got it home. So, bringing you up to present:

 

-replaced the master cylinder (runs again, needs starter fluid)

-replaced the fuel pressure regulator

-replaced the crank sensor

-replaced the distributor module

-replaced the ECM (this is what got it to start on it's own)

 

In getting in there, I've found it needs a couple of extra things, namely an alternator (no big deal) and the catalytic converter is clogged. I'm having my mechanic tear the cat out and re-weld the exhaust as the smog is current. Down the line I may put a new cat in and try to get it to pass smog legally.

 

If anyone wants to weigh in on anything I've just said or things I should look out for (nearby affected parts, preventative maintenance, etc.), please do. In the meantime, I'd really like to have an expert take a look at this and give it the "real" inspection it clearly needs.

 

CAN ANYONE RECOMMEND A RELIABLE MECHANIC IN THE LOS ANGELES AREA with real knowledge and expertise in XJ/MJ's? I'm hoping to find a specialist. Not looking for a build-out guru, more someone who knows the engine/electrical side of things top to bottom, though if they do it all, that's of course fine, too.

 

Thanks in advance and forgive any unintended noobness in this post.

 

Mauricio

I found this guy in named Mauricio who has a shop called Medico De Jeep in little Ethiopia. He's been working on my MJ for the last week doing an engine rebuild. He also works on my girlfriends Cherokee. He's awesome. Super reasonable with prices. All he does is Jeeps. He knows them like the back of his hand. I recently just picked up an 88. There's also a great parts place just for Jeeps called Jeep Parts Depot over in Pacoima. Picked up a cluster for a lot cheaper than I've been seeing them on ebay. 

 

[ratty]

2 hours ago, crumbscomanche said:

hey just saw this thread. shoot me a message and I'm happy to help out. I've got a garage and have figured out how to do a few things now. I also have a great mechanic on pico and fairfax I can refer you too for anything big. 

 

I think we just mentioned the same dude. 

[MuchRespect]

39 minutes ago, ratty said:

 

Mauricio

I found this guy in named Mauricio who has a shop called Medico De Jeep in little Ethiopia. He's been working on my MJ for the last week doing an engine rebuild. He also works on my girlfriends Cherokee. He's awesome. Super reasonable with prices. All he does is Jeeps. He knows them like the back of his hand. I recently just picked up an 88. There's also a great parts place just for Jeeps called Jeep Parts Depot over in Pacoima. Picked up a cluster for a lot cheaper than I've been seeing them on ebay. 

 

Thanks, guys! I found his old shop on Yelp but it didn't say where he moved to. I'll definitely check him out. Also, there seem to be a fair amount of LWBs in LA. Rad to see!

[crumbscomanche]

21 hours ago, ratty said:

 

I think we just mentioned the same dude. 

I go to Auto Service Pro Center down the way from Little Ethiopia. The owner is awesome (I've got plans to go wheeling with him) and it's a AAA certified shop so if you're a member any repairs are warrantied for 50k miles/24 months and you get 10% off on parts. But I usually just bring him whatever I need taken care of and he just charges labor. 

[ratty]

3 hours ago, crumbscomanche said:

I go to Auto Service Pro Center down the way from Little Ethiopia. The owner is awesome (I've got plans to go wheeling with him) and it's a AAA certified shop so if you're a member any repairs are warrantied for 50k miles/24 months and you get 10% off on parts. But I usually just bring him whatever I need taken care of and he just charges labor. 

 

That's awesome. Thanks for the tip