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hard time starting when warm

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Old Nov 9, 2008 | 02:14 PM
  #1  
cheap87's Avatar
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Year: 1987
Model: Cherokee
Engine: 4.0
Default hard time starting when warm

i have issues when the motor is warm starting. i8n the mornig it starts right up but after about 1/2 hour it will crank for 2 to 30 secs b4 starting. thouhgt it was a pluged fuel filter, it seemed to help but still does it every now and then. could it be an electric prob? i know my fuel pump is working good and i have the right amount of fuel psi along with a comlete tune up that was just done. any one have any ideas what it could be?
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Old Nov 9, 2008 | 02:31 PM
  #2  
matejcekautoworks's Avatar
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Year: 1991
Model: Cherokee
Engine: 4.0
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i would guess a o2 sensor, but thats just my 2cence
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Old Nov 9, 2008 | 02:35 PM
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From: In yourz postez fissin jurr spelinzs
Year: 1990XJ/1989MJ
Model: Comanche
Engine: 4.0L Renix
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The engine has to have a few things before the computer will allow it to start. The starter has to have spun the motor up to 300 RPM first. The CPS has to have sent 3 pulses to the computer so that the crank and the cam can be determined to be in the correct relationship and there needs to be adequate fuel pressure at the regulator.
Once all these criteria have been met the computer puts signal pulses to the injectors and turns on the coil to transmit spark to the plugs.
Knowing this about your Renix will allow you to check all the above things for proper signals and pulses. These all being met your Renix always has taken a few seconds to start, but that is the nature of the beast.
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Old Nov 9, 2008 | 02:37 PM
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BlueXJ's Avatar
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From: In yourz postez fissin jurr spelinzs
Year: 1990XJ/1989MJ
Model: Comanche
Engine: 4.0L Renix
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Originally Posted by matejcekautoworks
i would guess a o2 sensor, but thats just my 2cence
That only comes into play after the engine is running and will affect the idle and fuel economy.
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Old Nov 9, 2008 | 02:43 PM
  #5  
c-loss's Avatar
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Year: 1988
Model: Cherokee
Engine: 4.0
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thanks blue not even my thread and you taught me something today. i was just gonna recomend the coil on the last couple vehicles i had thats what it was anyhow.
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Old Nov 9, 2008 | 03:17 PM
  #6  
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k, cause i know on some of my other trucks that has caused problems
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Old Nov 9, 2008 | 04:10 PM
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Default thnx

thnx guys i realy needed a point in the right direction. ill check those things out.
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Old Nov 9, 2008 | 04:15 PM
  #8  
Jabo's Avatar
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From: Chattanooga Tn
Model: Cherokee
Engine: 4.0
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mine did the same thing and found out it was the Cps.Bought one at a local partstore and ended up haveiong to go get one from the stealership.
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