Laredoed

Hello everyone. I have a 97 Laredo I6 which ran fine two days ago but would not start yesterday morning.

The GC cranks with no problems but it will just not start. There is fuel at the rail but the noid lights show no injector pulse. The in-line spark checker flashes when connected between the high voltage coil wire and ground. However, there is no spark indicated when the device is connected between a spark plug wire and the spark plug. The cap and rotor are newly installed because I noticed, as I first began checking out this problem, that the spring loaded contact in the center of the cap was completely worn down. There were no stored codes when I connected the Obdii reader.


Cam sensor? Crank Sensor?


I should also note that I did set off the alarm the morning it would not start. I dont know if that comes into play here.



Any input here would be greatly appreciated!


Thanks!

Bustedback

Unlock the passenger door with the key, I think your rig is in theft mode.

Laredoed

Unfortunately, the lock is broken on the passenger side. Additionally, the lock actuators do not work for the driver or passenger side front doors. Thats how I tripped the alarm - I pressed the key fob "lock" button which set the alarm but did not lock the drivers door. When I tried the door it opened and set the alarm off. I used the key in the ignition to make the horn stop beeping.

I read on this forum about turning the key in the drivers, passenger, or rear gate lock back and forth a couple of times. I did that to both the drivers and tail gate locks. It has not made any difference. I don't know how the condition of the actuator may affect this solution.

I have also read about grounding the purple and yellow wire to disable the alarm and I thought I might try that.

What I did not get a good understanding of was what exactly was disabled by the alarm. Is it just a fuel shut off? Or does it shut the ignition too? Does it disable the fuel pump or cut power to the injectors?

Thanks!

Laredoed

I guess the alarm issue was a bit of a red herring. I took off the door panel to search down the infamous purple wire with the yellow tracer. Not wanting to cut the wire, I removed some of the cover to expose the wire and held it against ground and attempted to start the vehicle. Still no start. I tested the voltage at the wire and it showed battery voltage. I decided not to make a permanent ground here and just taped up the wire and put it back into the harness. Reinstalled the door panel.

Took another reading for spark. pulled the two pin connector going into the coil. Got no voltage going into the coil with the key on. Got only a momentary battery voltage with cranking the engine. This voltage quickly dropped to zero. Used the inline tester light to check between the coil and the distributor again and basically got a "no spark" condition.

This, combined with the no injector pulse condition, prompted me to replace the crank position sensor CKP/CPS.

Started right up as if nothing was ever wrong.

Extra long extension with swivel head on 11mm socket made quick work of the replacement.



Thanks for all the great info on this site!

Bustedback

Finally! A guy willing to do some diagnostic work before throwing parts at a vehicle. Usually the first thing replaced for a no spark condition is the coil, then the injectors and o2 sensor. All of those parts being replaced with no diagnostics done, only bad advise. Good job to you sir!

warped156

I have a 95 xj and I have no spark. I was thinking it was the crank sensor but I don't wanna just spend the 70 bucks without being sure. Now a few weeks ago I went wheeling and got into some deep water and some deep mud. The computer got wet and I was wondering if the computer would cause no spark too. Is there away I could check the computer to see if it's good? Thank you.

Bustedback

believe it or not, but the PCM is pretty water proof. Buy if you got deep enough to get the PCM wet you also got the distributor wet too. The crank sensors on a Jeeps are almost a wear item, when in doubt, replace it with a quality replacement. The cam sensor is a finicky sensor that will cause a no spark too. It is right under the distributor cap and is super easy to replace.

warped156

Thanks man. That makes me feel better haha. I am going to start with the crank sensor. But thanks again for your response.