CKP already bad? - JeepForum.com
 
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post #1 of 12 Old 03-25-2020, 11:25 PM Thread Starter
thapropellerguy
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This past summer I was having issues with my 1998 4.0 ZJ stalling and it turned out it was the crankshaft sensor, so I replaced it with a Mopar CKP and didn't have any more problems. That was until this past Monday (3/23), I was out of town for the 5 days previously but didn't drive it on the trip. When I got back and went to start it my battery was completely dead, wouldn't even jump.

I had someone give me a ride to buy a new battery and once I put it in I got a full charge in the gauge and all accessories, dome lights, gauges, etc working but now have a no crank no start. Searching shows may be a CKP issue, but would one really fail that quickly?

Before I go diving into troubleshooting I was wondering if anyone has experienced this happening after having it sit that length of time. That was the longest it hadn't been started or driven (other than a long fiasco with a harmonic balancer) so it seems odd to me that would happen. It didn't even appear anything had been left on to drain the battery so I'm stumped.

Any insight would be very helpful.


Better late than never.
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post #2 of 12 Old 03-26-2020, 12:48 AM
Zilliver
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Any codes?
Do you have impulse on the coil plug if you crank?

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post #3 of 12 Old 03-26-2020, 06:05 AM
jtec
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I would not think it is the CKP if the engine does not crank.

Be sure it is in P or N - sometimes moving the shifter will help get it started if switch (NSS) is acting up. Checking at the starter relay is an easy location to check starter circuits.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #4 of 12 Old 03-26-2020, 07:26 AM Thread Starter
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Quote:
Originally Posted by Zilliver View Post
Any codes?
Do you have impulse on the coil plug if you crank?
No it isn't throwing any codes, but what do you mean by impulse on the coil plug?

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post #5 of 12 Old 03-26-2020, 07:35 AM Thread Starter
thapropellerguy
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Quote:
Originally Posted by jtec View Post
I would not think it is the CKP if the engine does not crank.

Be sure it is in P or N - sometimes moving the shifter will help get it started if switch (NSS) is acting up. Checking at the starter relay is an easy location to check starter circuits.
Well it is actually cranking, just not starting. But the way it sounds when I try to turn it over sounds like when I'd crank it after a stall when the CKP was initially bad.

I know I already have an issue with my NSS which is giving me issues.

Better late than never.
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post #6 of 12 Old 03-26-2020, 08:04 AM
CJ7-Tim
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The CKP can be tested.

For 1996+ 4.0 L Jeeps, the OBD engine computer (ECU/PCM) re-boots, and the idle settings are deleted, when you: (1) let the battery run down by leaving the lights or radio on, (2) disconnect the battery for an extended period of time, (3) when the battery goes bad and needs replacing, (4) when the alternator is not properly charging the battery, (5) or when poor battery connections result in a voltage drop at the PCM or poor battery charging. Loose, corroded, or damaged battery cables or ground wires may also cause or contribute to the problem.

A faulty Coolant Temperature Sensor may also cause similar symptoms. Testing of the CTS is recommended as part of the diagnostics. A poor ground at the ignition coil can also cause similar symptoms.

The reboot symptoms are: (1) having difficulties starting the engine without depressing the gas pedal, and (2) the engine will have a low idle and probably stall unless you keep your foot on the gas pedal. (3) The ECU will usually relearn the idle settings after a short period of driving and the engine will start and idle normally.

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 or connectors and replace as needed. Copper wires should be copper color, not black or green. Do the same for the grounding wires from the starter to engine block, the ground wires at the coil, and the ground wires from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds.

If the symptoms reoccur, you need to have your battery and/or the alternator Load Tested at a repair shop or auto parts store. This is usually a free service they offer to bring in potential customers. Handheld testers are very inaccurate and will usually pass marginal alternators. Even with low battery voltage, the engine will start, but the ECU can re-boot multiple times and a new battery may be required.

Cleaning the Idle Air Controller (IAC), regular tune-ups, and using fuel injector cleaner should be part of your routine preventative maintenance for smooth starts.

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post #7 of 12 Old 03-26-2020, 08:40 AM
jtec
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ok you have engine cranks but no start.

Is there spark at several plugs?
What is fuel pressure - post PSI.

Could try - as someone cranks to start, spray carb cleaner or brake clean into TB - did the engine fire and try to start on the spray?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #8 of 12 Old 03-26-2020, 06:14 PM Thread Starter
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Quote:
Originally Posted by jtec View Post
ok you have engine cranks but no start.

Is there spark at several plugs?
What is fuel pressure - post PSI.

Could try - as someone cranks to start, spray carb cleaner or brake clean into TB - did the engine fire and try to start on the spray?
I read one way to check if the CKP is faulty is there would be no spark to ANY cylinders. All cylinders had spark so that potentially rules that out.

I put a pressure tester on the fuel rail and had my gf crank it and was registering 42 PSI, from what I understand it should be between 30-45 PSI.

Lastly I tried spraying starting fluid in the throttle body while she cranked and it didn't turn over.

So where should I go from here? I've heard this sort of thing could throw off timing. Is this possible?

Better late than never.
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post #9 of 12 Old 03-26-2020, 10:35 PM
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49PSI +-5psi. so you are low.

You did confirm spark at all 6 plugs?
When spraying - you said engine did not crank turn over?
'crank' 'turn over' means the engine spins. i am confused it no longer cranks (spins) ?

Why would suspect it jumped time - did you work on the engine recently?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #10 of 12 Old 03-27-2020, 12:19 AM Thread Starter
thapropellerguy
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Quote:
Originally Posted by jtec View Post
49PSI +-5psi. so you are low.

You did confirm spark at all 6 plugs?
When spraying - you said engine did not crank turn over?
'crank' 'turn over' means the engine spins. i am confused it no longer cranks (spins) ?

Why would suspect it jumped time - did you work on the engine recently?
I guess I confused my terminology and what not. In any case I solved the problem. I was told to look into my security/key and so I found a forum post that said to try resetting the system by locking and unlocking the tailgate with the key and another poster said they kept cranking until it started.

So I locked and unlocked the tailgate and then got in kept cranking until it finally started, just returned from driving down the street and back. Sorry for any confusion and thanks for the suggestions.

Better late than never.
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post #11 of 12 Old 03-27-2020, 02:31 AM
Zilliver
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The security module does not stop the car from starting up - it will stop it after about 2 seconds of running.

So you still have a problem somewhere.

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post #12 of 12 Old 03-27-2020, 10:54 AM
jtec
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I agree with above - glad the jeep is running.

Maybe a scanner to look for codes would be a good idea. Cant hurt.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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