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  #1  
Old February 19th, 2008, 12:16
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1998, Long crank time, only some of the time?

Hey everyone. I've got a '98 XJ (obviously), 4.0, auto, 108k on it. Sometimes (only when hot), it will crank for about 5 seconds before starting, others its a half a second....any clues?

Thanks.
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  #2  
Old February 19th, 2008, 13:06
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Re: 1998, Long crank time, only some of the time?

tough with what little info you give, but I would first suspect the battery.

have it load tested, replace if necessary.
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Old February 19th, 2008, 13:07
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Re: 1998, Long crank time, only some of the time?

You do know you are not supposed to touch the gas pedal when starting right ?
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Old February 19th, 2008, 13:11
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Re: 1998, Long crank time, only some of the time?

Check valve on the fuel pump is most common on the 1997-01's. Heat soak is another problem. Leaky fuel injector is possible, but not very common.

Use the SEARCH function.
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Old February 19th, 2008, 13:23
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Re: 1998, Long crank time, only some of the time?

Most likely a fuel pressure issue. If you turn the key to on, you should hear a brief hum....that's the fuel pump priming the system. When that hum ends about 10 sec later, see if you still have the issue. My guess is that the problem will stop. I know it seems annoying, but I see the same problem in my '94 XJ and my '93 Honda Civic....so I don't think it's just a Jeep issue. I will say that I recently changed the injectors in the Jeep and it seems to be less noticeable. Perhaps it's just the 10 year old O-rings not sealing quite as well as they used to.
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Old February 19th, 2008, 14:14
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Re: 1998, Long crank time, only some of the time?

hot soak

edit just read Tim's
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Old February 19th, 2008, 14:27
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Re: 1998, Long crank time, only some of the time?

Intermittent long crank? Check the following:
  • Battery voltage while cranking should be 9.6VDC or higher
  • Grounds should all be clean. A valve cover leak can cause slow cranking - the battery-engine ground is near the dipstick
  • Check the rest of the grounds - a weak sensor ground can also cause you trouble
  • Make sure the starter motor is mounted tightly, and that the contact between the starter motor and engine is clean. That's the ground return for the starter motor...
  • "Heat soaking" an electric motor will cause it to slow down, if it's starting to get weak. Something else to think about - it is just about ten years old now...

To rule out loss of fuel pressure, turn the key to ON when you expect a long crank, and wait about two seconds. This allows the fuel pump to pressurise the fuel system - which will effectively eliminate that as a problem. However, my first thoughts are electrical, rather than fuel-related - I'd probably check the battery (especially if it's more than four years old) or the starter motor (if OEM) first.
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Old February 19th, 2008, 14:48
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Re: 1998, Long crank time, only some of the time?

I would probably have to go with the checkvalve on the fuel pump. Change quite a few of those around here for long crank times. you can hook your fuel pressure guage to the rail and turn the key on for a few seconds and then turn it off and see if the pressure holds.
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Old February 19th, 2008, 15:53
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Re: 1998, Long crank time, only some of the time?

I have a 1988 ...is the fuel pump checkvalve a separate enity or is it part of the fuel pump?
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Old February 19th, 2008, 16:38
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Re: 1998, Long crank time, only some of the time?

Quote:
Originally Posted by B.RAIDER
I have a 1988 ...is the fuel pump checkvalve a separate enity or is it part of the fuel pump?
If you have an 88, you have a RENIX rig - and long crank times are a quirk of programming, so not a good deal you can do about them. Upgrading mains has been shown to help - if you're still running OEM mains, your connections are deteriorating (they're, what, 20 years old?) and that can make your starter crank slowly.

Most of the same advice given earlier applies - but moreso. You're twice as old! You won't be able to get rid of all the "slow crank" issues (the key one is programmed into the system itself,) but you can still do a lot.
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Old February 21st, 2008, 10:30
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Re: 1998, Long crank time, only some of the time?

It's got a new fuel pump, new battery, everything is tight and clean (haha). Like I said, it only does it once the motor is hot, and then, only some of the time...?
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Old February 21st, 2008, 10:40
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Re: 1998, Long crank time, only some of the time?

I bet dollars to donuts it has to do with your fuel preasure. It's either in the seals of your injectors or it's your preasure regulator. It's probably loosing preasure over time while its off. After it builds preasure its fine.
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Old February 21st, 2008, 10:42
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Re: 1998, Long crank time, only some of the time?

Quote:
Originally Posted by White1998XJ
It's got a new fuel pump, new battery, everything is tight and clean (haha). Like I said, it only does it once the motor is hot, and then, only some of the time...?
Only when it's hot? Ok, i'm stumped.. Unless it's vapor locking
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Old February 21st, 2008, 10:55
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Re: 1998, Long crank time, only some of the time?

When the motor is cold, it starts in less then 1 second. Now say I drive it for twenty minutes, turn it off, and come back to start it 15 minutes later, (not everytime...) it'll crank for like 5-10 seconds before starting.

This isn't my first XJ, but this is the first time one has ever done this....
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Old February 21st, 2008, 16:59
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Re: 1998, Long crank time, only some of the time?

Quote:
Originally Posted by White1998XJ
When the motor is cold, it starts in less then 1 second. Now say I drive it for twenty minutes, turn it off, and come back to start it 15 minutes later, (not everytime...) it'll crank for like 5-10 seconds before starting.
Instant cold start rules out the check valve. Heat soak and/or vapor lock can happen even in winter. Do you get winter blend gasoline ? Does it run roughly for 15-30 seconds and then clear up and idle normally ?
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Tim MAY be 100% correct, but why would a person automatically pick him as the expert .....
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