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Unread 06-23-2009, 03:05 PM   #1
austtill
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how to check cps on 92 cherokee 4.0

hey guys is there a way to check the cps on a 92 cherokee.i replaced the fuel pump but it still will not start and stay running and i do not want to spend the money on a new one please help me thanks.

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Unread 06-23-2009, 03:16 PM   #2
LeftOfCenterXJ
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I stole this from tim, but:

Quote:
Originally Posted by CJ7-Tim View Post
Crank Position Sensors can have intermittent “thermal failure”. This means that the CPS/CKP fails when engine gets hot, but works again when it cools back down.


Symptoms
- Starter cranks and cranks but engine won't start up
- Fuel gauge and voltage gauges may not work or display properly.
- You sometimes will have No Bus on the odometer after 30-60 seconds.
- A failed CPS/CPK may or may not throw a CEL trouble code.
- No spark at the spark plugs.
- Fuel pump will run and prime for 3-5 seconds.

If the CPS/CPK is failed sometimes the OBDII code reader cannot make a connection to the computer or cannot read Check Engine Light/MIL codes because the CPS/CPK has failed.


Diagnostic steps to confirm the CPS is the cause of your no-start


You should be able to verify a bad cps, by unplugging it, and turning the ignition key to on. If the voltage gauge and/or the fuel gauge now displays correctly, replace the CPS.

Unplugging and reconnecting the CPS sensor where it connect to the main harness near the back of the intake manifold usually resets the ECU and if the jeep fires right up after doing this you can bet that the CPS is the culprit and needs to be replaced.

Exchange the fuel pump relay and the ASD relay with one of the other similar ones in the PDC to eliminate the relays as the cause of the no-start Confirm that the fuel pump to runs for 3-5 seconds when you turn the ignition key to ON.

Eliminate the NSS as a cause of no start. Wiggle the shift lever at the same time you try to start. Put the transmission in Neutral and do the same. Do the reverse lights come on when the shifter is in Reverse?

Inspect the wires and wire connectors at the O2 sensors on the exhausts pipe. A short circuit from melted insulation or from broken O2 sensor wires can blow a fuse and the ECU/ECM will loose communication.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables and replace as needed. Do the same for the grounding wires from the battery and engine to the Cherokee's frame/body. Jeeps do not tolerate low voltage or poor grounds and the ECM/ECU will behave oddly until you remedy this.






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Unread 06-23-2009, 07:33 PM   #3
austtill
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can i check volts at connector.this thing is at the point i am about to junk it and call it a day.it will start run for a few seconds and die.then it will try but wont.turn the key on and off a few times and it will start for a few seconds.somebody please help before it becomes a twisted hunk of metal.
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Unread 06-24-2009, 08:19 AM   #4
CJ7-Tim
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CPS 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.

CPS TESTING PROCECURE for 1987 – 1990 4.0 L engines

Test # 1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 - 275 ohms. If the CPS is out of that range by much, replace it.

Test # 2 - You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without
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Unread 06-24-2009, 01:34 PM   #5
austtill
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ok so chared the battery and tried to start it and now i have no spark.the fuel pump comes on with key and runs when cranking what the crap.did the cps finally go help!!!!!!!!!!!!!!!!!!!!!!!
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Unread 06-24-2009, 02:10 PM   #6
CJ7-Tim
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Carefully read the above postings, all the testing info and procedures you need is right here in the thread.
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Unread 06-24-2009, 02:18 PM   #7
littleblackXj
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Why not just replace? It costs like $20 and takes about 10 minutes to replace. Plus it's a good investment because they tend to go out all the time.
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Unread 11-14-2013, 07:59 AM   #8
CHETA
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2002 JEEP WRANGLER SPORT 4.0L AT , cranks normal but will not start , ran great the day before. What can I check or do? Should I try starting fluid and if so where would I put it?
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Unread 11-20-2013, 11:32 AM   #9
CJ7-Tim
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Quote:
Originally Posted by CHETA View Post
2002 JEEP WRANGLER SPORT 4.0L AT , cranks normal but will not start , ran great the day before. What can I check or do?
See post #2 above, test the CPS.
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