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98 xj no start

mr.zxj

NAXJA Forum User
Location
akron ohio
Hi guys I have a 98 cherokee thats been for about 4or5 months now it wont start.the battery went dead so I charged it still not starting. So I started to trouble shoot it no spark. So I replaced the cap rotor crank sensor cam sensor coil tps sensor and the ecm and still nothing I checked all the fuses swapped relays around and cleaned the ground wires and still nothing. Im getting 12volts at the plug on the coil. Any advice would be greatful
 
Did you swap the ASD relay in the power distribution center?
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Spark: 12 volts from ignition switch to the ASD relay; when the key is first turned on the PCM provides a ground to the ASD relay to energize it, then the ASD relay passes 12 volts to the coil primary side. If no crank sensor signal is generated after a couple of seconds the PCM cuts the ground to the ASD relay (and fuel pump relay too) and that cuts power to the coil (and fuel pump). Key to START and once again the PCM energizes the ASD relay. Now, a critical element is the crank sensor--no signal from the crank sensor and the PCM won't trigger the coil to provide spark.
 
Is it an automatic? Might be the Neutral Safety Switch. You can test it by bypassing it at the connector near the back of the engine compartment. More details here.
 
Just because you replaced a sensor, doesn't mean the sensor plug or sensor wires are good.

More details are required:

When your Jeep won’t start :

1) Do all the gauges display correctly when it is not starting, or does the fuel gauge and/or voltage gauge not work at all, or not display properly ?
2) Does the fuel pump prime and run for 3-5 seconds when you turn on the key ?
3) Have you tried wiggling the automatic transmission shift lever when trying to start, in both PARK and NEUTRAL ?
4) When you turn the key does nothing happen, and you hear no sounds ?
5) Does the starter not engage, and you only hear a clicking sound from under the hood ?
6) Does the starter engage, make the starter sound, and cause the engine to turn ?
7) Does the engine sputter and try to run, or does it not start or run at all ?
8) If you depress the gas pedal about halfway during starting, does the engine start up and run ?

Answer yes/no to all by the numbers.


Have your helper turn the key to start the engine while you gently tap on the starter with a hammer. If the engine starts, you need a new starter. If wiggling the automatic transmission shifter starts the engine, you need to clean or replace the Neutral Safety Switch (NSS).

Get your Volts/Ohms multimeter. With the key in the ON position, check for voltage directly at the starter. If you have approximately 12.0 volts or more battery voltage at the starter, the problem is may be the starter. If you have no voltage at the starter, the NSS and the ignition switch are suspect and need to be inspected/tested. If you test less than 12.0 volts at the battery with the engine off, the battery is weak and needs to be charged or possibly replaced. The starter, alternator, and battery can all be load tested at the auto parts store.
 
#1 no fuel and volt gauges stay to the left they work before I parked it. #2 couldn't hear it but I stabbed the relief valve and fuel shot out definitely had pressure#3 yeah tried that #456 yes the starter cranks it doesn't try to start just cranks #78 no .also I replaced the nss last summer had tyranny shift problems. I got a question for u im getting 12volts at the coil plug but nothing coming out as far as spark why is that? Thanks
 
Condensation in dizzy cap?

Pull your cps plug and plug it back in?

I had this happen on an 89 and my CPS was fubar. Fixed that and got spark.

Seems to me 12 volts goes to the coil all the time, is that a correct assumtion? I thought thats what was happening with my 89.

Maybe some moisture got into your CPS connection
 
The PCM coil driver opens and closes the coil circuit on the primary side of the coil, inducing voltage into the secondary winding of the coil to produce a spark. So you can have 12 volts at the coil input , but no spark if the PCM is not driving the coil. The PCM runs the show using inputs from all the other sensors.
 
Again, I will suggest a timing light as it can verify that the coil is firing... You can tag it onto the high tension lead from the coil to the distributor and verify it that way or, just tag it onto one of the plug leads. Personally, at this stage, I would put it on the HT lead from the coil.

We know you have fuel from your release of the pressure at the schrader valve. Need to verify the spark.

As is the case with everything on the Heep, battery voltage is at the device and the device is controlled by the PCM toggling the ground. So, yes, there needs to be a nominal 12VDc at the coil. If you do not have access to a timing light but have a friend that has a Heep, borrow the coil just to eliminate it. Do not just go out and buy one as electrical parts are non-returnable.

It seems counterintuitive to controll things this way but there is a very good Electrical Engineering reason behind the decision to go that way.
 
Ok but I have already bought one and switched it out again. But should I hook it up to a plug wire as normal or the high tension wire is that the plug that plugs into the coil.im thinking the crank sensor is bad even though its new.
 
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