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Old April 18th, 2005, 19:59
Matthew Currie's Avatar
Matthew Currie Matthew Currie is offline
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Join Date: May 2002
Location: Vermont, land of big clay
Posts: 7,014
Re: 1989 jeep cherokee Laredo need help plz

Quote:
Originally Posted by Kinamien
Well after being flamed off the full size jeep site I posted....
Ok well its a 1989 jeep cherokee laredo...4.0 6 cyl. The problem....The engine started one day then dead the next....I changed the plugs gap'd .035 changed the oil....replaced the muffler.now it turns over but doesnt fire? any suggestions for this poor first time Jeep wannabe mechanic...
A good place to start is to determine whether or not you have any spark. One of the most common failures of the 4.0 you have is the crank position sensor, which the computer uses to set the timing. You'll get no spark without it. It's located on the bell housing, kind of tucked under the firewall, at about 1 o'clock as you stand at the front of the Jeep looking back. To begin with, you might try just unplugging its lead and replugging it. It isn't hard to figure out which plug it is if you have located the sensor itself. It leaves the wiring harness and kind of disappears down behind the engine on the driver's side. Sometimes just umplugging and replugging it will scare it temporarily back to life. If it does, you should still replace it as soon as you can. It's a bit hard to reach, and frustrating to do the replacement, but it's possible without exotic tools or skills. For further information, try searching this site using "CPS". It comes up often. Or report back to this thread, and I'm sure you'll get plenty of advice.

Of course it could be something else too, but this is a good thing to check first. If you have an ohmmeter, check the resistance between terminals A and B of the sensor (unplugged). It should read 125-275 ohms. If it reads shorted or open, it's toast.
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