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[Mattg]

I have a electrical problem on my 1995 jeep Cherokee xj 4.0l which is causing a no spark I am wondering where is the best place to get a wiring diagram from cheers

[JamesH]

search the internet for workshop manual, you should find a dodgy pdf version to download with wiring diagrams in.

A few things kill the spark on purpose (if that's the right term) - failed crank sensor, failed cam sensor, immobiliser. A scan of the OBD computer should bring up a fault code for a failed sensor if that's the problem and I think on your age of XJ you can get the fault codes to display on the dash. Have a look in the technical reference library section on here for a guide to doing that and the list of codes.

[Mattg]

I have changed crank shaft and cam shaft sensors, new ht leads, new spark plugs, new rotor arm, new dizzy cap and new coil still nothing the car turns over and fuel pressure is correct at the fuel rail. All the dash lights work and gauges work correctly along with all the lights that go off just before cranking like check engine and abs. The car only come with one key no fob how will I tell if I have an imobaliser? I have tryed the key diagnostic but I am struggling to understand the pauses and not pauses is there anyway I can upload a video on here for help thanks

[Mattg]

Got the jeep running today it was the signal wire from the crank position sensor I bypassed it with some wire and it run great took it for a drive turned it off Tryed to turn it back and just turning over again not running coming up with code 11 there is the correct voltage here and a good earth I am scratching my head again now

[Jonny Jeep]

You can test the crank sensor if you have a multimeter. If you disconnect it and measure resistance between the b and c terminals it should be above 10k ohms.

[Mattg]

After disconnecting the crank position sensor and testing terminal to the sensor its self at b to c I am getting 1.1 ohms does this mean my new sensor has packed it's bags?

[Jonny Jeep]

The FSM recommends using an analogue meter for the test set at 10k ohm range and that the sensor should show open circuit. I've tested mine in the past with my auto ranging digital meter and it showed open circuit. I think my meter goes up to 40Megohm.

If it is at 1.1 ohms I'd say it's failed. Was it OEM or aftermarket? Many on the US forums won't use aftermarket parts because of quality/longevity issues.

Here's the text from the 95 XJ FSM regards the CKP sensor test.

CRANKSHAFT POSITION SENSOR TEST
To perform a complete test of this sensor and its
circuitry, refer to the DRB scan tool. Also refer to the
appropriate Powertrain Diagnostics Procedures manual.
To test the sensor only, refer to the following:
The sensor is located on the transmission bellhousing
at the left/rear side of the engine block (Figs. 2, 3
or 4).
(1) Near the rear of the intake manifold, disconnect
sensor pigtail harness connector from main wiring
harness.
(2) Place an ohmmeter across terminals B and C
(Fig. 5). Ohmmeter should be set to 1K-to-10K scale
for this test. The meter reading should be open (no
resistance). Replace sensor if a low resistance is indicated.

[Mattg]

It was an aftermarket one for a car spares shop it has only been on the car for a 20 min drive would it go so soon? And what causes them to go? Thanks

[Mattg]

When I plug the sensor in I am getting continuity to ground from the signal wire but when unplugged I am not does this mean the ecu is not getting the correct reading from the sensor and earthing it?

[Jonny Jeep]

I don't know how the connections to the PCM would behave connected or not. I just know there sensor has a ground, a 5V supply and the signal to the PCM. As far as testing it other than the test described above the only I can think to test it would be an oscilloscope to view the output signal. Might be worth going back to where you got it and showing them it fails the test as described in the FSM. After only a short time I think under Sale of Goods Act it is not of satisfactory quality.

SInce you've had it a very short time I think that's the route I would go. And I'd test an replacement offered before accepting it. If a replacement didn't show open circuit I'd reject that and ask for a refund.

What causes them to go? As I said quality issues.

[JamesH]

There have been issues with sensors other than the Jeep / Mopar ones and there is advice on lots of forums to only fit the original sensors.

I've only ever changed one and bought a Mopar one from the dealership.

[Mattg]

My thanks for the help changed the sensor one turn of the key and fired straight up one happy jeep owner again now and got my sensor swapped so didn't cost me thanks again

[gregwho]

Great outcome!

 

[Jonny Jeep]

Good news. Hope this sensor lasts longer.