1994 xj no spark

[lady in gray]

We have a 94 xj automatic 4.0 2wd replaced crank sensor, coil, pick up/cam sensor, computer, relays, and still no spark. She will turn over all day but no fire. Started about a week ago on and off but now, Nothing. Please help, she's all we got and if I miss to much more work, my boss will go from understanding to taking applications.

 

[birchlakeXJ]

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.

 

[BatmanXJ]

I had this happen to me. Sorry for non technical terms but I'm not a Mechanic I am just inclined to fix my own issues most of the time.

There is a wire (actually set of 3) coming out of the top of the distributor that is under the Distributor. the distributor has a notch for the wires to come out. but apparently the PO put the Cap on and pinched the wires. They were bare and touching each other. I split the 3 wires apart and taped them individually and re installed the Dis Cap and runs like a top now. I would have take pictures and posted a tutorial but I was on the trail when this happen to me. I can not tell you what those wires go to but I'm assuming something with the computer. I have never come across an engine that has wires coming out of the top like that. Just looking at the cap with it installed it actually looks like a wire is caught under the cap.

 

[Geofux]

Have you checked the codes on your jeep?

I found this resource useful: http://go.jeep-xj.info/HowtoECUcodes.htm

I spent a lot of time messing around with mine to get it running, and finally pulled codes which helped out tremendously.

 

[lady in gray]

Only codes are 12 and 55... In other words, nothing.

 

[lady in gray]

Batman, those wires go to the pick up / crank sensor. Having them pinched would cause a no spark condition and your Jeep would die.
Not a big deal now but just some info for the future.

 

[BatmanXJ]

Mine did die on me that's how I figured out the issue. I thought maybe that could be your issue.

 

[lady in gray]

Still not starting. As I stated, New computer, ADS relay, fuel pump relay, fuel pump, crank shaft position sensors .... yes sensors, cam sensor / pick up coil, 2 ignition coils, plugs, wires, cap & rotor. Still no spark!!!!! HELP!

 

[GrimmJeeper]

have you tested the crank sensor with a meter? it's pretty common around here for them to be bad out of the box from the cheaper parts stores. a simple test with a multimeter will tell you if it's bad or not.

 

[birchlakeXJ]

Ignition "switch" is still in play here too.....

 

[lady in gray]

4 crank Sensors 2 from the dealer. Ignition switch should not be a problem as it still turns over and fuel pump still kicks on. We had her towed to a shop and all the mechanics are scratching there heads. We are running out of options as she may be headed to the crusher next week. PLEASE, SOMEONE HELP US SAVE OUR JEEP!!!

 

[Ecomike]

If you are not getting any spark from the High Voltage coil, why are you spending time on money on fuel pumps, etc?

Have you check the fuses?

Looks for any physically damaged wires, especially near the exhaust manifold.

Are you sure there is no spark, how did you check for spark?

If there is spark, it may be flooded, if it is, floor the gas peddle and crank until it starts in 10 second intervals (give the battery and starter time to cool off), that turns off the injectors and un-floods the engine till it fires.

 

[lady in gray]

We have checked for spark with a test light and the old fashioned way with the coil wire and a screw driver, with 2 sets of wires,then straight off the coil. All the fuses and relays have been replaced, all the grounds cleaned, inspected and nothing. It started as an intermittent issue now won't start at all, so we assumed it could be a bad wire and opened the entire wiring harness and did a test on every wire from end to end.(took 3 days) That's when she went to the shop.

 

[Ecomike]

So it has absolutely no spark at all?

 

[Jnida63]

you need to find someone with a scope and scope the pattern from your crank sensor, if you were in central ohio i would gladly scope it for you as i have a handheld scope.
one thing to check, did you make sure the distributor is turning when you crank the engine?
Also make sure you have 12 volts to the positive side of the ignition coil with key on and then check to see that the negative side is getting a ground pulse to fire the coil.
If not you have an electrical issue

 

[lady in gray]

No spark at all!!!
we figured it to be an electrical issue but don't know where to start looking

 

[Ecomike]

Well I must agree, this is sure one to check "make sure the distributor is turning when you crank the engine?" because one of the signals needed for spark comes from inside the distributor by 1994 IIRC, if the Cam gear is busted, the Dist would not rotate, and the ECU would be missing that signal.

I think the CPS signal can be partially tested with an AC digital meter.

Sounds like you need a set of FSM wiring drawings next and someone who can debug the wiring with a meter, the OLD fashioned way!

It could be as simple as a bad ground.

Did they ever check the wiring at the ignition switch, and the ign switch itself?

I forget what year the ICM under the HV coil was eliminated and moved to inside the ECU, but if 94 still had the ICM, you have not mentioned replacing it yet? It would be directly under the HV Coil.

 

[lady in gray]

JEEP for sale!

 

[Ecomike]

I just pulled out the wiring diagram, looks like a Bad:

Ignition switch (or bad wire connector at same)

or

Bad ASD Relay

Or bad Fuse #15, 30 amp, could be your problem.

Have you tried swapping in a used ECU from a junk yard?

Also looks like the 1994 still had an ICM directly under the HV coil, so if it has not been tested, or replaced, it could be a no spark problem.

 

[ihscoutlover]

Ok I had a similar problem Lady. Here is some of what I did/checked. I first had a no spark condition similar to yours. After the help from many on here, we diagnosed the Crank Sensor as my first issue. Got a Stealership one, and that problem went away. Then the cam sensor code popped up. Upon checking that one, I found that the rotor had an abnormal amount of play in the distributor. I put a whole new distributor in it and the cam sensor code was gone. Then things got interesting. I put in a couple of different ECU's. Now its got great new spark. Problem is that now the fuel pump has given up the ghost. No fuel pressure at the fuel rail. Upon adding 12volts to the pump directly, nothing happened. No noise, no nothing. The fuel rail did have pressure when I first started stuff, I depressurized it and found that its still not pressurizing. So Friday I go the the parts store, get a new pump and get it installed on Sunday. Then my XJ should be back in the game.

My thoughts, pull the cap and verify with someone cranking the engine that the rotor is turning. I would also check for play, as when I pulled the distributor out, I found that the shaft had worn the pickup enough that the signal wasn't even going anywhere. Check for play and verify that the rotor is turning. The only other issue I can figure is a bad ground. I checked grounding and operation on the relays, operation of the computer signals opening and closing circuits, and testing the actual relays. Crank and Cam sensors were bad, and if I had to do it over I can do it since I know the values and the procedures to verify its proper operation.

By the way, Lady, mine is a 1994 also. How much you asking for yours, since its having issues??

Jeff