Jeep died/won't start

[Ecomike]

You may be trying to restart too soon? There is timer that resets the ICM to a start position, probably takes a few seconds, and my daughters Saturn needs to be in the run mode for a bout 10 seconds before you crank or it will not start. I figure it is a computer / sensor control valve reset time delay involved. Renix 87-90 likes to be on while the fuel pump primes for 3-4 seconds before cranking.

I would focus on the MAP sensor subject top to bottom next. Then see what all it does. IIRC the later years were notorious for hidden vacuum tubing leak near the throttle body that feeds vacuum to the MAP sensor. If the MAP does not get immediate accurate vac data it will cause most of your problems.

 

[rwat96]

You may be trying to restart too soon? There is timer that resets the ICM to a start position, probably takes a few seconds, and my daughters Saturn needs to be in the run mode for a bout 10 seconds before you crank or it will not start. I figure it is a computer / sensor control valve reset time delay involved. Renix 87-90 likes to be on while the fuel pump primes for 3-4 seconds before cranking.

I would focus on the MAP sensor subject top to bottom next. Then see what all it does. IIRC the later years were notorious for hidden vacuum tubing leak near the throttle body that feeds vacuum to the MAP sensor. If the MAP does not get immediate accurate vac data it will cause most of your problems.

I have gotten into the habit of letting it prime for 1-2 seconds before starting because it starts roughly sometimes if I don't and it's been that way since I got it a year ago.
I will look into the MAP sensor vaccum then and I will let you guys know what the problem is when I find out.

 

[Ecomike]

"I have gotten into the habit of letting it prime for 1-2 seconds before starting because it starts roughly sometimes if I don't and it's been that way since I got it a year ago."

That I think indicates a fuel delivery system leak, not holding pressure after turning off the engine. The check valve, or pressure regulator valve which may be in the gas tank by 96? But you confirmed earlier 50 psi on the fuel pressure, so do that engine off leak down test to see if it is leaking, then see it is through an injector or the fuel pump check valve.

 

[rwat96]

"I have gotten into the habit of letting it prime for 1-2 seconds before starting because it starts roughly sometimes if I don't and it's been that way since I got it a year ago."

That I think indicates a fuel delivery system leak, not holding pressure after turning off the engine. The check valve, or pressure regulator valve which may be in the gas tank by 96? But you confirmed earlier 50 psi on the fuel pressure, so do that engine off leak down test to see if it is leaking, then see it is through an injector or the fuel pump check valve.

The 96 has a completely unique fuel pump system unlike earlier or later years, so i am not completely certain, but yes i believe it is in the tank. I have heard of people installing inline check valves on the fuel line because the check valves usually go before the pump does. Also yesterday we brought the jeep to the shop (because they messed up so they wouldn't charge anything so might as well let them try again), and right before it was towed it started running fine again and the shop found nothing wrong with it. I suspect that they changed the throttle body gasket originally because they prolly did a vacuum test and assumed that was it because they couldn't find anything else wrong with the vacuum lines. I did some research and on 96 and newer Cherokees the map is on the throttle body, so instead of a long vacuum line to the map on the firewall like in the Cherokees you have, its a small nipple connection that can only be found by removing the map. So with that the case i have trouble believing i could be getting an intermittent vacuum leak there, but if the problem arises again I will pull the map off and see if I can find any problems.

 

[Ecomike]

Bingo!!

"its a small nipple connection that can only be found by removing the map."

That is exactly where others with your problem have reported the leak here on Naxja over the years after agonizing days..weeks... of troubleshooting. I had just forgotten the details. It is the fact that it is hard to see with out removing the map that it gets it overlooked!!!!

 

[rwat96]

Bingo!!

"its a small nipple connection that can only be found by removing the map."

That is exactly where others with your problem have reported the leak here on Naxja over the years after agonizing days..weeks... of troubleshooting. I had just forgotten the details. It is the fact that it is hard to see with out removing the map that it gets it overlooked!!!!

I will check that then! I just don't understand how it would be intermittent if it is the problem

 

[Ecomike]

I will check that then! I just don't understand how it would be intermittent if it is the problem

Vibration, old tubing with loose fit that moves under variable vacuum. Back fires can move it....oily dirt near the leak...you would be amazed. That close to the MAP a tight seal is critical

 

[rwat96]

Vibration, old tubing with loose fit that moves under variable vacuum. Back fires can move it....oily dirt near the leak...you would be amazed. That close to the MAP a tight seal is critical

Ok so I replaced the rubber boot (that seemed undamaged) with some rubber tubing that fits really snugly so it isn't gonna be leaking. I am still getting the same symptoms as before. It idles erratically when coasting (idk if I said fthat before) and I have to either drive with two feet to keep the rpms up or gently feather the throttle when first starting to keep it from dying when starting from a stop. When just sitting it idles fine.

 

[rwat96]

Any thoughts anyone? I am pretty stumped at this point and I don't want to have to take it to an expensive dealership or jeep specialist. What else can cause the symptoms above?

 

[Ecomike]

Check the PM I just sent you.

 

[cruiser54]

MAP sensor could be bad. It can be tested. It has a huge influence on richness.

If this were my Jeep, I would get some contact cleaner and clean every electrical connector under the hood I could find. See Tip 3.

I would also clean the dipstick ground connections per Tip 1.

I know you're looking for a silver bullet cure, but as others are trying to tell you, it's necessary to perform diagnostics by a process of elimination.

www.cruiser54.com

 

[rwat96]

Without fully testing or troubleshooting that I suspected it could be it and I will test that for sure, it would be great it lt were that sinple. And all of the connections i have unplugged looked fine to me, but yes I probobly should inspect them closer and clean them, and I was planning on cleaning all grounds next. I should have more time to sort this out now that classes are out of the way, but that was the main reason for wanting a silver bullet cure, because I wanted some direction with the lack of time I had during the preceeding weeks.

 

[Ecomike]

MAP sensor could be bad. It can be tested. It has a huge influence on richness.

If this were my Jeep, I would get some contact cleaner and clean every electrical connector under the hood I could find. See Tip 3.

I would also clean the dipstick ground connections per Tip 1.

I know you're looking for a silver bullet cure, but as others are trying to tell you, it's necessary to perform diagnostics by a process of elimination.

www.cruiser54.com

That engine block dipstick ground even got me, not long ago, after 8 years of preaching about cleaning and refreshing Renix ground connections.

 

[rwat96]

That engine block dipstick ground even got me, not long ago, after 8 years of preaching about cleaning and refreshing Renix ground connections.

I will either start troubleshooting today or tomorrow. I haven't confirmed to what extent the shop tested the electrical system, but would bad grounds show up through a typical shops electrical run through or not? I will still clean the grounds anyways as one of the first things I do.

 

[Ecomike]

Without fully testing or troubleshooting that I suspected it could be it and I will test that for sure, it would be great it lt were that sinple. And all of the connections i have unplugged looked fine to me, but yes I probobly should inspect them closer and clean them, and I was planning on cleaning all grounds next. I should have more time to sort this out now that classes are out of the way, but that was the main reason for wanting a silver bullet cure, because I wanted some direction with the lack of time I had during the preceeding weeks.

What is your major? My son just finished his BS in Physics.

Keep in mind than some ground problems come and go, helps to test the live wires during a problem, by piercing the cover with a probe and testing for voltage on a ground wire that should be there, and for power loss on the power feed wires for on / off circuits.

Have you run an OBD-II scan for any pending codes? The blue tooth OBD gadgets on Ebay for about $10 are dirt cheap and use <$10 program app called Torque pro that is awesome.

 

[Ecomike]

I will either start troubleshooting today or tomorrow. I haven't confirmed to what extent the shop tested the electrical system, but would bad grounds show up through a typical shops electrical run through or not? I will still clean the grounds anyways as one of the first things I do.

Depends on the shop, 95% of the ones I ever tried were clueless scam artists.

 

[rwat96]

What is your major? My son just finished his BS in Physics.

Keep in mind than some ground problems come and go, helps to test the live wires during a problem, by piercing the cover with a probe and testing for voltage on a ground wire that should be there, and for power loss on the power feed wires for on / off circuits.

Have you run an OBD-II scan for any pending codes? The blue tooth OBD gadgets on Ebay for about $10 are dirt cheap and use <$10 program app called Torque pro that is awesome.

I just graduated highschool in a program that let's you take college classes, and I've got a full year of college out of the way. I plan to pursue a major in buisness administration for versitility, but I plan to pursue a career as a airline pilot, and I've already got my private pilots liscense

And yes that's true, that's how this problem has been since the beginning, sometimes it works, sometimes it doesn't, with varying degrees of severity. And I haven't myself, I assume the shop did and would have acted accordingly, but I will verify tomorrow when they are open. And in regard to your other response, they are honest and resonably priced, but my mom just reminded me of how they failed to figure out an electrical issue with a 2008 sequoia we have, the dome lights don't work and the clock resets each time the engine starts. So it seems this shop doesn't do well with electrical from our exprience.

 

[Ecomike]

Electrical issues, especially Electrical GREMLIN issues that have Romulan cloaking devices are especially nasty ones to catch and debug even for Mr Spoke LOL. It is an art, and takes sometimes days with factory wiring manuals and taking tons of stuff apart to find and fix a bad wire buried in the harness. Congrats on Graduation and the pilots license and college classes while in HS, I did the same thing in 1972 College classes)...party1:

I just graduated highschool in a program that let's you take college classes, and I've got a full year of college out of the way. I plan to pursue a major in buisness administration for versitility, but I plan to pursue a career as a airline pilot, and I've already got my private pilots liscense

And yes that's true, that's how this problem has been since the beginning, sometimes it works, sometimes it doesn't, with varying degrees of severity. And I haven't myself, I assume the shop did and would have acted accordingly, but I will verify tomorrow when they are open. And in regard to your other response, they are honest and resonably priced, but my mom just reminded me of how they failed to figure out an electrical issue with a 2008 sequoia we have, the dome lights don't work and the clock resets each time the engine starts. So it seems this shop doesn't do well with electrical from our exprience.

 

[rwat96]

Electrical issues, especially Electrical GREMLIN issues that have Romulan cloaking devices are especially nasty ones to catch and debug even for Mr Spoke LOL. It is an art, and takes sometimes days with factory wiring manuals and taking tons of stuff apart to find and fix a bad wire buried in the harness. Congrats on Graduation and the pilots license and college classes while in HS, I did the same thing in 1972 College classes)...party1:

I hope it doesn't end up being that much of a pain to fix, we will see. And thankyou!!

 

[Ecomike]

Most repair places specialize in just certain tasks that call for parts swaps on obvious bad parts. Leaking coolant pump, radiator, dead alternator.

Today's electronic controlled systems with computers, sensors, digital control devices, are the highest tech stuff there is, that would challenge even a hands on design and field service chemical plant systems engineer like me, much less an every day shop mechanic. Most Auto shops hate electrical gremlin issues like yours, because they can eat up $1000 in shop time and only take a 50 cent wire cut and solder job to fix. Hard to charge enough to even break even without the customer raising hell.