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Problems with 89 XJ - Need Help....

M

mybrosride

NAXJA Forum User
Location
Orange Co - SoCal
Looking for answers to possible problems with my 89 jeep 4.0L auto, having good battery and a good starter getting solid spark and fuel, fuel pump just replaced, and will not fire up or stay running. Mechanics are baffled hunting through wiring thinking pcm, anyone?

thanks....... :)
 
PCM can go bad, but it is rare. If the PCM was bad, you wouldn't be getting spark. Let's start from the beginning, although it sounds like you may not have the answers if the "mechanics" are baffled.

How do you know you have spark?

How do you know you have fuel pressure?

The other necessary component for combustion is compression. What is your cylinder compression?

DId it stop running directly after you replaced the fuel pump? Or before? Why did you replace the fuel pump?

Who is actually working on this? You and / or mechanics?

Have you tried spray start?
 
The mechanics are donig all the work....

Havent tried to spray start as I don't know what that is.

I was told by my mechanics I have spark and fuel.

My jeep was in perfect running health, has 94,000 miles on an 89, then I parked it one night after driving it that day, and it would turn over and try to start but not fire up. So i kicked the starter a few times and the fuel tank hoping to rustle up the fuel pump or the starter but that wasnt the issue apparently. So I had it towed to a local shop in Southern California. After that I had them replace the fuel pump because I thought it was making noise right before my truck didnt start, but it did not fix the problem, still could not get it running again. I did notice a slight pulley squeek I thought at first was my brakes but I just replaced all my brake parts 2,000 miles ago.

I have replaced almost every seal on the truck to make it stop leaking oil. I have also replaced the distributor and the power steering pump, some hoses and my belt.

The shop said they think it's electrical and their mechanic who has been trouble shooting it for the past 2 days almost got it started yesterday but then it putted out.

I really want my rig back! It was running great so this is quite perplexing.

Thanks again for the help.....
 
I suggest taking it to the jeep dealer--with the right test equipment, the problem should have been corrected in two days.
The Jeep dealer should have Renex-specific scanner to test ECM operation.
 
I'm with the previous post...check the compression. My son's '88 had much the same experience. We verified fuel pressure at the rail with a gauge, verified spark by pulling a plug and watching it, verified injectors firing with a noid light, then checked compression on a couple of cylinders...found it to be lower than I like. Then I remembered a trick a REAL mechanic taught me in my college days of part time work at a service station...

The mechanic taught me that when lots of cranking yields no start, often times the unburned fuel washes down the cylinder walls, removing the thin coating of oil that assists with achieving good compression. Not only that, but the unburned gas also gets into the oil sump, further reducing the ability for the oil to assist with good compression.

Well, long story short...we did an oil change, put a little bit of oil in three cylinders to assist, and I'll be damned if the thing didn't start right up!

You might want to pull your oil dip stick and give it a smell. If you smell gas, change the oil and then try to start it up.
 
Crank Position sensor? mine went bad but it still had spark, was pulling my hair out!
 
Flyfisher said:
I'm with the previous post...check the compression. My son's '88 had much the same experience. We verified fuel pressure at the rail with a gauge, verified spark by pulling a plug and watching it, verified injectors firing with a noid light, then checked compression on a couple of cylinders...found it to be lower than I like. Then I remembered a trick a REAL mechanic taught me in my college days of part time work at a service station...

The mechanic taught me that when lots of cranking yields no start, often times the unburned fuel washes down the cylinder walls, removing the thin coating of oil that assists with achieving good compression. Not only that, but the unburned gas also gets into the oil sump, further reducing the ability for the oil to assist with good compression.

Well, long story short...we did an oil change, put a little bit of oil in three cylinders to assist, and I'll be damned if the thing didn't start right up!

You might want to pull your oil dip stick and give it a smell. If you smell gas, change the oil and then try to start it up.
Click to expand...

I'm not doing the work on the car, the shop is doing the work - a certified techinican. He's pulling his hair out trying to pinpoint the problem... He's gone through so many areas, and so far the only thing he can possibly think it may be is a PCM... But he cannot narrow it down.
 
I don't care about your mechanics "certification", TAKE IT TO ANOTHER SHOP. A renix jeep is not that complicated. It should not take 1 whole day, let alone 2 whole days to diagnose a no start condition on any rig. This "mechanic" clearly does not know how to diagnose your jeep. Pay only for actual repairs and at most 2 hours of trouble shoot time, any more than that and they are a dishonest shop that should be reported to the Better Business Bureau and your state Attorny General. This shop is just trying to take advantage of a customer that doesn't know very much.

get references and call them before you let another shop touch your Jeep. Talk to customers that have a similar Jeep. Most shops are not familar with the Renix system, so they throw basic trouble shooting out the window and throw expensive parts at it instead of diagnosing the real problem.

Trust no one

Assume nothing

Find a mechanic that understands your Jeep!
 
plymatt65 said:
I don't care about your mechanics "certification", TAKE IT TO ANOTHER SHOP. A renix jeep is not that complicated. It should not take 1 whole day, let alone 2 whole days to diagnose a no start condition on any rig. This "mechanic" clearly does not know how to diagnose your jeep. Pay only for actual repairs and at most 2 hours of trouble shoot time, any more than that and they are a dishonest shop that should be reported to the Better Business Bureau and your state Attorny General. This shop is just trying to take advantage of a customer that doesn't know very much.

get references and call them before you let another shop touch your Jeep. Talk to customers that have a similar Jeep. Most shops are not familar with the Renix system, so they throw basic trouble shooting out the window and throw expensive parts at it instead of diagnosing the real problem.

Trust no one

Assume nothing

Find a mechanic that understands your Jeep!
Click to expand...
\

This shop is one of the best in Southern California.... I don't appreciate your comments about this place of business. They service more Jeeps than most Chrysler dealers
 
mybrosride said:
\

This shop is one of the best in Southern California.... I don't appreciate your comments about this place of business. They service more Jeeps than most Chrysler dealers
Click to expand...


Then why is it taking 2 days just to trouble shoot the problem?

Blind trust serves only the shop, not you or your Jeep. If this shop was so good, then you wouldn't be asking for help from stangers on the internet.

Nuff said
 
Here's the problem. You take your jeep to a shop to have it repaired. The shop apparently is not capable, so you bring your problem here. Basically, you're asking us to help the shop you are presumably paying to repair your jeep, as opposed to helping YOU, fix your jeep.
You need to be willing to do the "wrenching" yourself, to gain any lasting benefit from a Forum, such as NAXJA. We say, "check the fuel pressure". And you say, THEY say it's good. We say, check for spark, and you say they did. The thing is, you have not done anything but pass on what they SAID they did. Since it appears you have little mechanical know-how yourself, you really don't know what they did, or didn't do, just what they are telling you. Again, after two days, the hot-shot shop your defending has yet to solve the problem. It seems they can't even tell you if the ECM is working properly. Either They do not have the Renex-specific diagnostic tools, like YOU say THEY said they do, or they don't know how to use them.
Helping the shop you're paying to fix your jeep is not what this forums about.
Again, take the jeep to a Jeep dealer who has the RENIX-specific test equipment. Your Jeep has two diagnostic plugs under the hood specifically used by the dealer to analyse engine/ECM issues in a timely manner.
 
Not to agree with the people that are being sarcastic so please don't take it that way. I pulled a motor from a 98, swapped all electronics and manifolds and seals to my 89 and installed it in about 10 hours in my garage and it fired. two days with the proper equipment is questionable.

Now for the helpful part. you said you had a noise by the motor. If you are sure you have spark and fuel. the problem is likely timing. On a renix that could be as simple as a bad knock sensor or messed up distributor setting or worst case a timing chain that jumped a tooth. the computer can only compensate for a few degrees out. if the chain stretched or jumped it may fire but not be able to stay running or it may just crank and not start.
 
Kevinma255 said:
Not to agree with the people that are being sarcastic so please don't take it that way. I pulled a motor from a 98, swapped all electronics and manifolds and seals to my 89 and installed it in about 10 hours in my garage and it fired. two days with the proper equipment is questionable.

Now for the helpful part. you said you had a noise by the motor. If you are sure you have spark and fuel. the problem is likely timing. On a renix that could be as simple as a bad knock sensor or messed up distributor setting or worst case a timing chain that jumped a tooth. the computer can only compensate for a few degrees out. if the chain stretched or jumped it may fire but not be able to stay running or it may just crank and not start.
Click to expand...

the shop is overworked with other cars, they aren't working on it "non-stop", so its not an actual 2-day job...

And thanks for your input.... I had began to debate if sarcastic and smart-*** remarks were all I was going to get from asking any type questions I may ask in the future ;)
 
The way i read your first post was that the shop had the vehicle in a bay and it was getting constant attention. If it was just at the shop for two days that is diffrent.
 
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