1996 XJ Will Not Start - JeepForum.com
 
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post #1 of 13 Old 11-13-2016, 05:23 PM Thread Starter
moscarike
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1996 XJ Will Not Start

Hi all. I bought a '96 Cherokee nearly four months ago. Has 4.0 L, 251,596 miles, AW4, NP231. Ran when bought, but after about a month of sitting while work was being done to it it stopped running.

First there was no spark. The jeep would crank with no problem but just would not start. We checked for power to the CPS and found none so decided to install a new PCM. Once complete, we had spark.

Engine now cranks and will start for and run for about 1 second and then die. Here's a list of things that have been done since that point...

1. New battery and terminals
2. Grounds refreshed
2. New fuel filter, air filter
3. Fuel injectors cleaned and serviced; are all within spec; reinstalled
4. New fuel pump
5. New cap, rotor, plugs, and wires
6. New crankshaft position sensor
7. Fuel Pressure is about 45 to 50 psi
8. Tested IAC, TPS, MAP sensor; all OK
9. Does not seem to be the neutral safety switch
10. Runs on starter fluid
11. Power is good to the injectors
12. Compression is 150 psi at all cylinders

Any help is appreciated and welcome as I am baffled. Thanks!

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post #2 of 13 Old 11-13-2016, 05:47 PM
CJ7-Tim
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Some of the stuff below you have already done, but is included for future topic searches. Try feathering the gas pedal for a few minutes.




For 1996+ Jeeps,the OBD-II engine computer (ECU/PCM) re-boots, and the idle settings are deleted, when you: (1) let the battery run down by leaving the lights or radio on, (2) disconnect the battery for an extended period of time, (3) when the battery goes bad and needs replacing, (4) when the alternator is not properly charging the battery, (5) or when poor battery connections result in a voltage drop at the PCM or poor battery charging. Loose, corroded, or damaged battery cables or ground wires may also cause or contribute to the problem.

A faulty Coolant Temperature Sensor may also cause similar symptoms. Testing of the CTS is recommended as part of the diagnostics. A poor ground at the ignition coil can also cause similar symptoms.

The reboot symptoms are: (1) having difficulties starting the engine without depressing the gas pedal, and (2) the engine will have a low idle and probably stall unless you keep your foot on the gas pedal. (3) The ECU will relearn the idle settings after a short period of driving and the engine will sometimes start and idle normally.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Copper wires should be copper color, not black or green. Do the same for the grounding wires from the starter to engine block, the PCM, the ground wires at the coil,and the ground wires at the oil dipstick tube. You must remove, wire brush, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds.

If the symptoms reoccur, you need to have your battery and/or the alternator Load Tested at a repair shop or auto parts store. This is usually a free service they offer to bring in potential customers. Handheld testers are very inaccurate and will usually pass marginal alternators. Even with low battery voltage, the engine will start, but the ECU can re-boot multiple times and a new battery may be required.

Cleaning the Idle Air Controller (IAC), regular tune-ups, and using fuel injector cleaner should be part of your routine preventative maintenance for smooth starts.

“We the people are the rightful masters of both Congress and the Courts,
not to overthrow the Constitution but to overthrow the men who would pervert the Constitution” Abraham Lincoln, 1859.
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post #3 of 13 Old 11-14-2016, 10:02 PM Thread Starter
moscarike
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Thanks for the reply.

For the first month of ownership the battery was either dead or disconnected for periods of time, so I guess PCM re-boot is definitely a possibility. However a new PCM has been installed since, and the jeep has never started with this PCM. The battery has also been disconnected from this new PCM for periods of time.

I tested the coolant temperature sensor tonight and it is fine.

I'm assuming that you mean feathering the gas pedal while cranking so I tried that for a few minutes and the engine still fires up but dies immediately afterward.

Any further ideas?
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post #4 of 13 Old 11-15-2016, 04:57 AM
CJ7-Tim
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Once it starts, you will need to keep nursing the gas pedal until the PCM re-learns the idle settings. It might be able learn enough with an extended idle time, but a 5 minute drive will for sure give the PCM all the info it needs.

“We the people are the rightful masters of both Congress and the Courts,
not to overthrow the Constitution but to overthrow the men who would pervert the Constitution” Abraham Lincoln, 1859.
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post #5 of 13 Old 11-17-2016, 12:04 AM Thread Starter
moscarike
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While feathering the throttle, I crank until the engine catches and then release the key to the 'run' position. The engine will fire up for a split second but die immediately afterwards. After the engine fires up I continue to feather the throttle but it doesn't appear to make much of a difference; the engine just sort of sputters out. I am noticing some smoke coming from the exhaust pipe on most start attempts and from the engine bay occasionally. I have attached a video so that you and others can observe what it is happening for yourselves.

Simply copy and paste
youtu.be/BfG7O5CE3K4
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post #6 of 13 Old 11-18-2016, 05:41 AM
YY5RM
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Hello Friend Moscarike, nice to meet you. I suggest checking the circuit of the fuel pump series resistance.
Connect a cable from + 12VDC ignition to one of the terminals of the ballast resistor. If it is not kept on try with the other terminal of the ballast resistor.
In its model XJ the relay that bridges the ballast resistor should be activated at the moment of ignition, in the condition of maximum throttle opening and in other conditions, for this reason the fuel pump starts and then runs out of power.
Good luck in your diagnoses.
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post #7 of 13 Old 11-18-2016, 07:41 AM
CJ7-Tim
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The 1996 XJ does not have a ballast resistor, but checking the fuel pump voltage is a good idea.


Quote:
Originally Posted by moscarike View Post
..... The engine will fire up for a split second but die immediately afterwards. After the engine fires up I continue to feather the throttle but it doesn't appear to make much of a difference; the engine just sort of sputters out.


Lack of spark, lack of fuel, or ignition switch issues ? You will need a helper to turn the key while you check for spark and watch the fuel pressure and check the fuel pump voltage.

“We the people are the rightful masters of both Congress and the Courts,
not to overthrow the Constitution but to overthrow the men who would pervert the Constitution” Abraham Lincoln, 1859.
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post #8 of 13 Old 11-19-2016, 04:21 PM Thread Starter
moscarike
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Confirmed that I have spark.

Fuel pressure confirmed also, but I have some questions. When the key is turned to the 'run' position the fuel pressure jumps to about 48 psi and then will drop quickly (to 30 psi in about 15 seconds) and will continue to drop. Anytime the engine is cranked the pressure jumps back up to roughly 48 psi and then falls quickly again. Is it normal for fuel pressure to bleed off very quickly right after the ignition is turned on or the engine is cranked or should it hold?

Based on the fact that fuel pressure reached 48 psi when the ignition is on or the engine is cranked and some time looking at wiring diagrams, I am assuming that the fuel pump is getting the proper voltage and the ignition system is ok.

At this point I'm going to pull out the NSS and clean it and then reinstall it. I figure that it's worth a try.

Also, there is some sort of electrical connector that is loose in my engine bay. I did not take this off; it was like this when I bought it I just did not notice it until later. I don't see any place where it might connect. Any ideas on where this connects to and if it is important? I will attach a picture.

Again, thanks for all of the feedback and help. I appreciate it.
Attached Thumbnails
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post #9 of 13 Old 11-19-2016, 04:45 PM
CJ7-Tim
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The fuel pressure should hold somewhat, but the first thing go on a fuel pump is the check valve. AirTex and store brands are notorious for failing quickly. You should only buy genuine Jeep or Bosch fuel pumps.

Have you tested the CPS ? You should be using only genuine Jeep engine sensors. All other brands are suspect Chinese parts. "Lifetime Warranty" store brand sensors and parts are very often out of specification or even failed right out of the box.

Have you confirmed there is not an ignition switch issue ?

The spare plug is for the engine bay lamp assy that belongs screwed onto the hood in that open space.

A faulty/dirty NSS would result in the starter not engaging at all.

“We the people are the rightful masters of both Congress and the Courts,
not to overthrow the Constitution but to overthrow the men who would pervert the Constitution” Abraham Lincoln, 1859.
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post #10 of 13 Old 11-19-2016, 05:22 PM Thread Starter
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The new fuel pump that I installed about a month and half ago was an AirTex pump that I picked up from NAPA. That said, even if the check valve is bad shouldn't the jeep start still start since the pump is making ~50 psi upon cranking?

I replaced the crankshaft position sensor about two weeks ago with a sensor from NAPA and I don't remember the brand. Maybe Echlin or something like that. If the sensor that I put in were bad would it be right to say that I wouldn't have spark?
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post #11 of 13 Old 11-19-2016, 05:51 PM
YY5RM
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It can comptobar the activation of injectors by installing small pilot light bulbs in parallel in at least two injectors. You can prick them with pins so as not to damage the cable lining.
Another suggestion could be a damaged injector (Direct), to confirm it is necessary to disassemble the fuel distributor tube with its 6 injectors and start the pump. If leakage is positive, the fuel pressure drops and the lubricating oil in the engine is contaminated.
Luck.
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post #12 of 13 Old 11-19-2016, 06:22 PM
CJ7-Tim
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49 +/- 5 psi fuel pressure is the factory spec. My check valve has been failed for 3+ years and it still starts after cranking twice.

I don't trust any engine sensors that are not genuine Jeep. Even the NAPA sensor quality is not what it used to be. Most auto parts stores sell cheap crappy Chinese "Lifetime Warranty" parts that are poorly manufactured and are often out of specification, or even failed, right out of the box. The ones that aren’t faulty often have a short service life before they fail. Always buy top quality replacement parts and genuine Jeep sensors. Numerous threads detail long and frustrating searches for a "problem" that ended up being cured simply with genuine Jeep repair parts.

A Noid Light can be used to determine if the injectors are firing. A damaged or faulty injector would not cause a no-start and would likely trigger a Check Engine Light (CEL) trouble code.




Crankshaft Position SensorConnector (CPS/CKP)
.




.




CPS Testing

TESTING PROCEDURE 1991 –20014.0L H.O. engines

1. Near the rear of fuel rail, disconnect sensor pigtail harness connector from main wiring harness.

2. Place an ohm meter across terminals 2 and 3 (See Image). Ohmmeter should be set to the 10K-or-2OK scale for this test.

3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

.



“We the people are the rightful masters of both Congress and the Courts,
not to overthrow the Constitution but to overthrow the men who would pervert the Constitution” Abraham Lincoln, 1859.
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post #13 of 13 Old 11-26-2016, 01:29 PM Thread Starter
moscarike
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Hello again.

I tested my NAPA cps and the resistance was about 56.2 k-ohms so I purchased a mopar cps and installed yesterday. Once again tried starting to no avail. Started to question the PCM, which we had bought online. We figured that it was good because with it, the jeep had spark, without it, it did not.

Anyway, went to a junkyard this morning and picked up a PCM from a 1996 cherokee and installed and after about two cranks the engine fires right up!

Thank y'all for all of your help, it is greatly appreciated!
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