98 XJ Cranks But No Start No Spark, ASD Dead

[WhiteKnight2]

Ok, I have a friends jeep at my house that wont start. I have searched a lot of forums and found similar topics but I wanted to start this because none of the others really finished the thread an I haven't been able to resolve the issue.

He drove to my house in the jeep because we were going to fix the 4x4 linkage. When we figured out the 4x4 linkage was gone, (must have fallen off)we didn't have the parts to replace and it was raining so no pick and pull, we just took care of some other small things. We were going to go to the store and get something (beer) so he tried to start the jeep and it clicked because the battery was dead. I guess the light was on inside because the doors were open the whole time or key was on maybe. Anyway we hooked the battery charger to it and after a min or two tried to start and it would crank but not start. Let it charge for a bit longer and still nothing. I figured the CKS was the culprit because that seems to be the common trend so we ran to the parts store and grabbed one. replaced it and still nothing. So after some t/s I have found the following symptoms:

1. Fuel and Battery Gauges not working.
2. ASD Relay is not contacting. 12v is present but PCM is not grounding Blue/Yellow wire. Position C3 on PCM. The relay did contact yesterday for some reason but the jeep still did not start and fuel pump relay still would not contact. ASD hasn't contacted since.

3. Fuel pump relay not contacting.
4. Coil getting 12v but PCM not grounding.

Ive checked PCM to ground and it has continuity. Ive checked every single fuse including the passenger side kick panel. Ive checked the relays in the PDC. Ive checked the gauges and CCD (think that is what its called) by doing the press odometer reset button turning power on and releasing button to cycle the gauges and they all check out ok. Ive looked at all the wiring connections I could and haven't found a broken/damaged wire. Also checked all the grounds.

My thought is, what "checks" does the computer go through to close the ASD circuit, fuel pump circuit, and coil circuit to ground? maybe a sensor in this circuit is bad and not sending the signal to the PCM to ground these circuits.

I cant really throw money at it by replacing sensors left and right so please help me with advice that is relevant.
Im hoping the PCM isn't bad but it seems weird that the ASD contacted yesterday for a while and hasn't since.

Any advice/help would be awesome.

[Mudderoy]

CEL on? If so can you get the code(s)? Is the speed sensor hooked up? You changed the CKS or CPS? The common issue is CPS.

[4.3LXJ]

What year Jeep?

[WhiteKnight2]

CEL is not on.

Speed sensor is hooked up (this is the one on the output of t-case correct?).

I checked all the connections/wires at the transmission and T-case in the case that we may have bumped something checking the linkage for 4x4.

We replaced the CKS (Crankshaft Pos. Sensor)

Have not replaced the CPS (camshaft pos sensor. This is also called the Pickup coil or switchplate if I remember correct)

I will test the CPS shortly. Would this keep the PCM from giving ground to said systems?

[WhiteKnight2]

What year Jeep?

98 Sport 4.0

[4.3LXJ]

Check for spark to see if you have the ignition working

[drakan1908]

Since you was working around trans. case/transmission area check the shift lever position switch(sorry drew a blank on the real name). Maybe a wire was knocked loose.


sent from a van down by the river

[WhiteKnight2]

Check for spark to see if you have the ignition working

I don't have 12v going to the coil. The Grn/Orn stripe wire is dead. It comes from the ASD relay so if it isn't contacting then there will be no spark.

[denverd1]

Since you was working around trans. case/transmission area check the shift lever position switch(sorry drew a blank on the real name). Maybe a wire was knocked loose.


sent from a van down by the river

neutral safety

[drakan1908]

neutral safety
Thanks. [emoji106]

sent from a van down by the river

[WhiteKnight2]

If t were the NSS it wouldn't crank correct? It is cranking just no spark or fuel.

I also do not have 5v coming from the PCM for the sensors in either the primary or secondary pins.

[drakan1908]

If t were the NSS it wouldn't crank correct? It is cranking just no spark or fuel.

I also do not have 5v coming from the PCM for the sensors in either the primary or secondary pins.
Kind of a guess. I was trying to think of anything under there that could cause a problem. Yea it wouldn't crank if the NSS was messed up.

sent from a van down by the river

[Mudderoy]

Since you was working around trans. case/transmission area check the shift lever position switch(sorry drew a blank on the real name). Maybe a wire was knocked loose.


sent from a van down by the river

It wouldn't turn over with a bad NSS (Neutral Safety Switch) would it?

[Mudderoy]

CEL is not on.

Speed sensor is hooked up (this is the one on the output of t-case correct?).

I checked all the connections/wires at the transmission and T-case in the case that we may have bumped something checking the linkage for 4x4.

We replaced the CKS (Crankshaft Pos. Sensor)

Have not replaced the CPS (camshaft pos sensor. This is also called the Pickup coil or switchplate if I remember correct)

I will test the CPS shortly. Would this keep the PCM from giving ground to said systems?

I don't know. I've never had to get into electrical signals when figuring out a no start issue.

I guess you've moved the relays around? Swapping the ASD relay with another next to it?

It might be worth removing the positive cable from the battery and then taking that cable and touching it to ground for a few minutes. That should reset the PCM and clear it's learned values.

I have to wonder what a bad ASD relay would do to the electrical signals though.

[WhiteKnight2]

I don't know. I've never had to get into electrical signals when figuring out a no start issue.

I guess you've moved the relays around? Swapping the ASD relay with another next to it?

It might be worth removing the positive cable from the battery and then taking that cable and touching it to ground for a few minutes. That should reset the PCM and clear it's learned values.

I have to wonder what a bad ASD relay would do to the electrical signals though.

The relays are all fine. I have moved them around and also checked them with 12v and they all contact fine.

I have tried the battery cable (+) to Ground trick with no luck.

The ASD relay didn't short its just not getting the ground from the PCM so I don't think it would have caused any damage, more of a symptom of the unknown issue.

I have unplugged every sensor one at a time on the 5v signal circuit and it did not change the voltage. (I heard this is a good way to track down he issue to an individual sensor). No Luck...

Im really starting to lean towards a bad PCM.... I know its rare but it happens..

[WhiteKnight2]

It seems weird to me that the PCM isn't sending 5v to the sensors when the key is in the run position. I would think it would have to have 5v to the sensors to run its "checks".

Does anyone know the logic of the PCM and how it runs through the system before it lets power go to the 5v? This could be helpful in determining what sensors could be bad or if it in fact the PCM. I cant find any info on this.

[4.3LXJ]

Yes, in the run position it should sen 5V to all sensors

[Mudderoy]

I keep wondering if this would be a bad ignition switch. I've just never had this issue.

[denverd1]

bad NSS cuts power to everything. wouldn't crank with a bad or out of adjustment NSS

[WhiteKnight2]

Yes, in the run position it should sen 5V to all sensors

Thanks. I thought so also.


I keep wondering if this would be a bad ignition switch. I've just never had this issue.

I thought of this as well. I had the ignition switch go out on my 95 and it would start as long as the key was in the "start" position but as soon as I let it spring back to the "run" position it would die. The "run" position had burned/melted and it was an open circuit. Of course it happened while being pulled over by a county deputy in the middle of winter.

This jeep however doesn't seem to get lose ignition power but I will definitely take it apart and double check.
Just want to exhaust all options before I go buying parts.