jimmpinoy

Hello from Doha Qatar. I am new to the site and my first time to start a thread. I have a 96 XJ, auto trans, 4I. MY jeep died suddenly and i can't seem to get it running again. Fuel pressure is ok and I have replaced the CPS already but still no spark. When I check the voltage between the input to the ignition coil, at ignition ON position its 0 volts and when I start to crank, the voltage becomes 5 volts. Any idea what seems to be the problem? Will appreciate all help. Thanks.

DFlintstone

I hear after sometime in 97 it won't help with the engine. The first page in "info threads" is one place it lists them. Worth a shot, good luck! (OBD is on board diagnostics, btw)


1991-1995 are OBD-I (Chrysler)

1996-2001 are OBD-II (Chrysler)

The "Key Tricks"
Older (OBDI) models - Start with the ignition off. Within five seconds, switch the key on, off, on, off, on. ("On" is NOT "Start" and "Off" is NOT "Lock"). The "check engine" light will flash. Count the flashes. Each code is a two digit code, so a (for example) 23 would be FLASH FLASH (pause) FLASH FLASH FLASH (long pause). It will never flash more than 9 times, so watch for those pauses!

Newer (OBDII) models - Put the key into the ignition, push down the odometer reset button, then turn the key to RUN with your finger on the button - and then release the button. The odometer will go through 1111111 through 999999, then display the car's serial number. It will then show the error codes (it might show them starting with P). If this method does not work, try the OBDI method.

Added;, fuses to things like the rear 02 sensor can blow and cause other things to fail. The wires back there take a beating, and at the front one its HOT! (Lol!)

xjbeans

Crank position sensor look it up sounds like it to me

freegdr

possible cam position sensor/halleffect sensor pick up coil key on key off check for codes as stated earlier ...

tjwalker

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.

stev-o

X2

freegdr

another thing to check seeing crank position has been replaced all ready and still no start the wires to rear o2 sensor will get rubbed thru causing short to ground causing one of the smaller fuses in pdc box under hood to blow causinga no start issue...

jimmpinoy

Correction PLZ...mine is a 6I, 96 XJ. My apologies.

DFlinstone, Freegdr, stev-o, xj beans, tjwalker: My car is OBDI. My error code is a 12 which am having since I bought this car. O2 sensor is gone, wire (already fried) hanging which i also cut from near the main wire terminal to erase doubts of shorted wire etc.

CPS is already replaced though i bought a new one again thinking i got a bad CPS the first time. I still didn't install the second CPS not until i can figure out why I have 5 volts only across the ignition coil. I am worried my PCM is gone reason i only have 5 volts in the ignition coil.

Cam position sensor is not available in my city; will have to wait when available so i can replace it too but am sure when finally i will get the spark, then the next concern will be the cam sensor incase the car won't start after the spark is back.


Thanks!

Radi

Disconnect the primary (+) wire from the coil and measure the voltage while starting. Does it come up to 12, or remain at 5?

Radi

Hang on.....Are you measuring between the primary terminals on the coil (at the connector)? 5-6 volts that way is normal....the (-) side is switched on and off to ground.
You should measure 12V between the (+) primary terminal and ground.

DFlintstone

Jim, 12 is "12 Battery disconnected. Battery or power to the ECM disconnected in the last 50 key cycles." Idk, maybe it set that if you disconnected the battery while you were working on it.

You have a boatload of fuses. Sorry I can't offer any direction, just check the little ones also!

My Renix has a 5 volt feed from (it's ECU, you have a PCM). Yours may have something similar. Hopefully Radi or someone can fill in. It may be the 12V power is only for the first two seconds, (while you are hearing the pump run), then continues cranking, and after the pcm sees a signal from the cps telling it it's running.

(PCM is grounding the asd relay to power injectors and ignition)

I know that's confusing, anyway I'd be checking fuses, and the wires to that rear 02 sensor as well. Those grounding might blow an important fuse.

I found something. There's 4 mini fuses in your PDC under the hood. Check the 15 amp one nearest the edge, nearest the relays. An 02 heater wire grounding can blow that and cause the asd to fail to provide power. I think!

Radi

The 96 has a 5 volt line too- any OBD will have it. TPS uses 5V, MAP sensor, etc. Scanner port has a 5V pin...
You are correct about the ASD- it powers up for a few seconds when the key is turned to "start". If the PCM doesn't see the engine running shortly, it turns the ASD back off. No crank sensor signal = no ASD relay = no coil power.

But...I'm not sure that's the problem...waiting to hear what the voltage is at the coil primary, measured to ground.
OP says it's 5 volts, but if measured across the coil primary, that's pretty normal. The (-) side of the primary is only grounded part of the time...the PCM disconnects the ground momentarily to fire the coil.
The actual voltage across the primary switches from 12 to 0 to 12 to 0. 5 or 6 volts would be an average, which the meter is probably displaying.

If there is 12V at the coil primary (+) to ground, and 5-6 volts across the primary, yet no spark...I'll go with a bad coil. Or bad coil=>cap wire. Or bad cap and/or rotor. Etc.
If there is 12V between the coil primary and ground AND 12V across the primary, the coil isn't being switched off of ground by the pcm, therefore the CPS isn't functioning, or the PCM coil driver is shot.
If there is less than 12V at the coil primary, will have to trace backwards through the ASD relay to see where the dropoff is.

jimmpinoy

The voltage between + terminal of ignition coil and negative ground is 12 volts. I tried to purchase a new ignition coil this afternoon but unfortunately the last stock they have in the store has damaged insulators. Since Friday in Qatar is equivalent to Sunday for other countries, meaning I won't be able to get hold of a new ignition coil until Saturday morning. I'll keep you posted guys for any developments. Thanks again to all.

jimmpinoy

Update folks!

The jeep finally starts yesterday after replacing the ignition coil.

Lesson learned: When engine is hot, never do the car wash right away especially if you want to clean the engine with water. Let the engine cool down first before going to the car wash. This happened too from a friend which I just learned yesterday. His wrangler also conked out 1 km away after the car wash. Same problem, the ignition pack is gone.

While I did not wash my engine with water when it conked out, I was trying to splash the radiator with water when i reached home after driving a couple of hours midday at 47C (116F); normal in middle east during summer. The engine temp was around 225F.

Again to all jeeperz who share valuable inputs, my sincere thanks. This site is indeed a great TRIBE!!!!

Signed:

Jimm from Qatar.

DFlintstone

And the crowd cheers! Well done! Thanks for getting back, and go find some shade!