Hey guys, just picked up a new jeep. '98 xj auto.

Weird problem..

When cold, it starts w/no problem. Runs fine. If I shut it off, and try to restart within 10-15 mins or so, it will start then, idle really rough and eventually die. No matter if I give it gas. After it dies, it will crank and crank, but no start. If I wait 15-20 mins, it starts right up and runs good.

I did a search, but don't even know where to start. Could it be a bad fuel pump?

Also has another issue w/tranny but I don't think that's related..

TIA

 

Did the car throw a code?

 

No codes..

 

Hmmmmmm, maybe fuel presure or injectors? I don't know, but if it were me I think I would start with checking my fuel pressure and see what I find there.

 

I would definately check fuel pressure, if its a duty cycle pump it only kicks on and pumps when it needs to. It may be running and gettin hot and shutting off, that's what the one in my mustang did, but its duty cycle urs may not be. I've only been a jeep owner for 2 months but buying mine at an auction I've learned a lot already about them

 

This is the key here. You are suffering from a thermal (heat related) failure. Now just to figure out what.

The top two thermal fail suspects on the 4.0 are the ignition coil and the crank sensor. Cam sensor is probably #3.

WHEN the vehicle doesn't start, it would be recommended to test the above components to see if you can find one that is out of spec.

I keep an old hair dryer in the garage for troubleshooting this type of thing. I run the hair dryer on the component and keep taking test data as it warms up. I've isolated more than a few bad components in this manner.

Here is some interesting information about your camshaft position sensor that may come into play here.

If the signal from the camshaft position sensor is lost while the engine is running, the computer will calculate spark timing based on the last cam signal and the engine will continue to run. However, the engine will NOT run after it is shut off. This kind of fits your scenario, yes?

So be sure to test your cam sensor! Especially if it runs great from the first time it starts until the first time you turn it off!

The cam sensor is located inside of the distributor. You will need a manual and a meter to test this.

Be sure to check back and let us know what you find!

 

Yes, you are right. Thanks for the info!! I really appreciate it! I'll give it a shot and post up what I find..

 

starter might be going out. that what mine did when it was going bad.

 

If this happens only when HOT and not when you start the engine cold, it really does sound like "heat soak".

This was a common problem on 1999-2001 cherokees, I'm not sure how much it applies to your 1998 but it could have the revised intake that gave the problems. Jeep came up with a TSB and a lame fix of wrapping the #3 fuel injector, but it doesn't truly fix the problem for most. Helps a little for a mild case. Here you go..........
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TSB 1803103 - 4.0L ROUGH ENGINE IDLE AFTER RESTART FOLLOWING A HOT SOAK
Date: 09/05/03 (supercedes 1802702 dated 09/06/02)
Model Year(s): 1999-2004

Description: NOTE: This bulletin applies to vehicles equipped with a 4.0L engine. This bulletin involves the installation of a fuel injector insulator sleeve.

Details: Customers may describe a 20 to 30 second rough idle following the restart of a heat soaked engine. This condition may be most noticeable when the engine is restarted following a prior 10 to 20 minute heat soak in hot ambient conditions of approximately 32 C (90ºF) or higher. This condition may be consistent with short city stop-and-go driving trips and can be aggravated by the use of fuel with a high ethanol content. Depending upon various conditions a MIL may occur due to DTC P0303 - Cylinder #3 Misfire.

This condition may be caused by heat from the exhaust manifold that following engine shut down migrates to the area around injector #3 and causes fuel vapor to form within the injector. This in turn may cause a momentary misfire of cylinder #3 until the fuel vapor is cleared of injector #3. The insulator sleeve lowers the injector #3 temperature to a point below which the fuel will not normally vaporize.

If vehicle exhibits a rough idle, and if a misfire of cylinder #3 is observed following a 10 to 20 minute hot soak, perform the Repair Procedure.

Parts required:
56028371AA Ignition Wire Shield

Repair procedure:
1. Cut insulator sleeve, p/n 56028371AA, to make two (2) insulator sleeves about 25-30 mm (1 in.) in length. See diagram.
2. Install one sleeve around injector #3, with the slit on the upward facing side of the injector. Install the other sleeve with the slit on the downward facing side of the injector.
3. Confirm sleeve is flush to intake manifold surface around injector.
4. Check injector #3 wire and ensure that the injector is rotated to a 2 o'clock position.


TSB for the cold start rough idle and P0303 code: TSB 18-010-01
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Heat soak generally doesn't result in a no start though. It usually manifests itself in a rough start.

I really think this is a thermal failure here...............

 

ah i didn't catch the no start part. Rock on.