replaced crank sensor and still wont start -
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Unread 09-17-2009, 03:13 PM   #1
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1999 XJ Cherokee 
Join Date: Sep 2009
Location: motor city
Posts: 2
replaced crank sensor and still wont start

F&$%# please help.My jeep died while driving so I tested the crnk sensor with my ohm meter which read bad sensor so I put in a new one and still no vroom.Its getting fuel and was getting spark now no spark. The battery and fuel gauges dont move when power is applied, which I heard points to the crank sensor.Also replaced plugs,wires,cap,and rotor.Any suggestions? Now I cant afford to get it towed and diagnosed.

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Unread 09-17-2009, 05:27 PM   #2
It's the crank sensor!
tjwalker's Avatar
1999 XJ Cherokee 
Join Date: Nov 2007
Location: Central Minnesota, MN
Posts: 8,610
Get back to basics. Spark + fuel + compression = start.

Let's assume that compression is okay since it just died while running. How did you check for spark?
Pull a spark plug. Keep it attached to the plug wire and place the electrode of the plug near a good engine ground. Have a buddy crank the engine while you watch. You are looking for a strong, blue, snapping spark. Orange isn't good.

A quick and dirty test for fuel is to spray a small amount of starter fluid into the intake. If the engine starts and runs momentarily, you have a fuel delivery problem.

Once you know exactly what you are missing, it makes the suspect list a whole lot shorter.

If the crank sensor signal isn't making it to the computer, you will not have spark OR fuel to the injectors. Cleaning the connectors for the crank sensor is something you can try. Use electrical contact cleaner. Remember that there is also a crank sensor connector under the hood near the firewall #6 injector. Corrosion of either of these connectors can inhibit the crank sensor signal from making it to the computer. How exactly did you test your crank sensor and what resistance readings did you get?

Try removing the connector for the crank sensor and turn the key on and see if that allows the battery and fuel gauges to work again. If it does, then you absolutely need to focus on the crank sensor CIRCUIT, not just the sensor. That means sensor, wiring, connectors.

Good luck and post back what you find.
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Unread 09-17-2009, 06:20 PM   #3
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1999 XJ Cherokee 
Join Date: Sep 2009
Location: motor city
Posts: 2
Well for spark I took the ignition coil wire off the distributor (still connected to the coil) and stuck a screw driver in the wire then held the screw driver to the block(this has worked before) and no spark.Bad coil? Starter fluid did nothing.I followed chiltons instructions to test crank sensor with my ohm meter terminals b and c I think, should have gotten open line but was getting resistance for every senario(a&b,a&c,b&c).To be sure, I tested the new sensor before install and I got open line-only when I had neg. probe on terminal b and pos. on terminal c, and was reading some resistance when I had pos. on term.b neg. on term.c- is this normal?I disconnected sensor,turned key, still no amps or fuel.Should I open the ecm to check for cracked solder connections?How do I check the coil? I also swapped the ASD relay with cooling fan relay.
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Unread 09-18-2009, 02:44 AM   #4
Real Jeeps have dents.
CJ7-Tim's Avatar
2000 XJ Cherokee 
Join Date: Apr 2002
Location: out in the garage - Minneapolis, Minnesota
Posts: 22,588
The ECM/PCM/ECU is sealed and there is nothing to look at. There have been a few cases of the ECU failing at the same time as (because of ?) a failed CPS and the Cherokee needed a new CPS and a replacement ECU. You should continue to inspect and test before you spend any money on an ECU.

CPS Testing

Crankshaft Position Sensor Connector (CPS/CKP)

TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (See Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

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Unread 10-28-2013, 08:31 AM   #5
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1999 XJ Cherokee 
Join Date: Oct 2013
Location: Pinson, Alabama
Posts: 1
any outcome to this. dealing with same issue
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