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  #1  
Old November 25th, 2018, 20:06
prescarlton prescarlton is offline
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'98 4.0L Auto Crank but no start

I've been searching the web for a few weeks now to find an answer to my problem. Before I throw more money into my XJ, I want to be sure I know it's the CPS that's gone bad.
tl;dr: gauges and dashboard lights act funny, jeep cranks but doesn't start.

Background - Jeep hasn't run in 3 years, got it for free off a buddy of mine. New battery, starter, cleaned out the NSS, I have a good ground, battery is not dead (I just left it at Advanced auto last week to get a deep cycle charge). However, the jeep cranks but does not start. Sometimes it won't crank at all, just make a noise as if it's trying to crank but can't. The fans move about an inch when this happens. I removed the belt to see if any pulleys were seized or anything similar, only one that is stuck is the alternator. However, the jeep won't run without the belt (I know it shouldn't run for long, but it won't run at all, just crank and crank). In addition to that, the gauges and dashboard lights only turn on when the key is in the run position and even still it only works sometimes and after it sits in the run position for a few seconds.

Both of these combined seem like a textbook example of a bad CPS to me, but I wanted opinions from y'all considering how I've only been an XJ owner for a few weeks now. My only other thought was a bad fuel pressure regulator, just based off of what the PO told me about the Jeep (engine intermittently cut out at 2500 RPM). TIA.
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Old November 25th, 2018, 20:56
4x4JeePmaNthINg's Avatar
4x4JeePmaNthINg 4x4JeePmaNthINg is offline
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Re: '98 4.0L Auto Crank but no start

Pull every wire that goes from the battery, body ground,starter, alternator, engine block and clean all contacts very well. Test all wires as they could be corroded if they aren't newer.

Is the starter factory? If it cranks regular it's likely fine.

You can test the CPS "crank position sensor" there are a few good threads out there on this.
If it's bad buy Mopar the first time.

Your fuel pressure regulator is built onto the pump. Sometimes you can test a bad pump by cycling the key to run 4-5 times to prime the fuel line before trying to start.

Last edited by 4x4JeePmaNthINg; November 25th, 2018 at 21:08.
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Old November 25th, 2018, 21:07
lawsoncl lawsoncl is offline
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Re: '98 4.0L Auto Crank but no start

Quote:
Originally Posted by prescarlton View Post
I've been searching the web for a few weeks now to find an answer to my problem. Before I throw more money into my XJ, I want to be sure I know it's the CPS that's gone bad.
tl;dr: gauges and dashboard lights act funny, jeep cranks but doesn't start.

Background - Jeep hasn't run in 3 years, got it for free off a buddy of mine. New battery, starter, cleaned out the NSS, I have a good ground, battery is not dead (I just left it at Advanced auto last week to get a deep cycle charge). However, the jeep cranks but does not start. Sometimes it won't crank at all, just make a noise as if it's trying to crank but can't. The fans move about an inch when this happens. I removed the belt to see if any pulleys were seized or anything similar, only one that is stuck is the alternator. However, the jeep won't run without the belt (I know it shouldn't run for long, but it won't run at all, just crank and crank). In addition to that, the gauges and dashboard lights only turn on when the key is in the run position and even still it only works sometimes and after it sits in the run position for a few seconds.

Both of these combined seem like a textbook example of a bad CPS to me, but I wanted opinions from y'all considering how I've only been an XJ owner for a few weeks now. My only other thought was a bad fuel pressure regulator, just based off of what the PO told me about the Jeep (engine intermittently cut out at 2500 RPM). TIA.

Long shot, but pull the horn relay.
https://www.cherokeeforum.com/f2/clo...isfire-181970/ Could be bad ignition switch - do the normal idiot light lite up when you first turn the key?
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  #4  
Old November 26th, 2018, 08:36
prescarlton prescarlton is offline
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Re: '98 4.0L Auto Crank but no start

Quote:
Originally Posted by 4x4JeePmaNthINg View Post
Pull every wire that goes from the battery, body ground,starter, alternator, engine block and clean all contacts very well. Test all wires as they could be corroded if they aren't newer.

Is the starter factory? If it cranks regular it's likely fine.

You can test the CPS "crank position sensor" there are a few good threads out there on this.
If it's bad buy Mopar the first time.

Your fuel pressure regulator is built onto the pump. Sometimes you can test a bad pump by cycling the key to run 4-5 times to prime the fuel line before trying to start.
Starter is a remanufactured CarQuest. It cranks regularly and sounds fine.
I'll pull all the wires and go through that this weekend (finals week at school so no time during the week). Thanks for the tip.
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Old November 26th, 2018, 08:39
prescarlton prescarlton is offline
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Re: '98 4.0L Auto Crank but no start

Quote:
Originally Posted by lawsoncl View Post
Long shot, but pull the horn relay.
https://www.cherokeeforum.com/f2/clo...isfire-181970/ Could be bad ignition switch - do the normal idiot light lite up when you first turn the key?
I'll try pulling the relay too. And no, when I first turn the key nothing lights up. The only thing that cuts on is the interior lights, headlights (sometimes), and radio. If I turn the key to run though, then the odometer and engine light etc light up.
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