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highlander93
New User
Apr 7, 2012, 3:51 PM
Post #1 of 4
(2317 views)
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jeep 4.0 wont run
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we have a jeep cherokee, year 2000 ,4.0 automatic transmmision. ok we just recently rebuilt entire engine ,new pistons ,main and rod bearings ,oil pump,timing chain,cam lifters ,everthing..truck started right up ,ran great,drove for about 4 weeks ,devloped and oil leak in the rear of the engine,,thought it was the soft plugh on the cam ,so we pulled the tranny ,changed the soft plug ,put it back together,started it up still had an oil leak .so we pulled the pan .changed the rear main seal ,,,doesnt seem to leak except now it wont run!!!!!!!,this it what we have changed, crank position sensor,cam position sensor,coil rail, pcm unit,,,,took the tranny back out cleaned the ring on the flexplate ,put back together ,still same problem ,,,engine starts for about 5 seconds ,then quits,try to re start and it bucks and acts like the timing is way off ...i am stumpped...please jeep world help...this is my sons truck ,we have a fortune in it ,,,its lifted 9 inches ,has 35 s tires ,long arms everything a boys toy should have ,we would really like to get it running good again so he can enjoy it again,,,please thankyou
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Hammer Time
Ultimate Carjunky
/ Moderator
Apr 7, 2012, 4:12 PM
Post #2 of 4
(2301 views)
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Re: jeep 4.0 wont run
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Make sure you don't have a security light on or flashing when this happens.
All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can ONLY be tested during the failure. Any other time and they will simply test good because the problem isn't present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.
Every engine requires spark, fuel and compression to run. That's what we have to look for.
These are the basics that need to be tested and will give us the info required to isolate a cause.
1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.
2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.
3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.
Once you have determined which of these functions has dropped out,
you will know which system is having the problem.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Apr 7, 2012, 4:13 PM)
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highlander93
New User
Apr 7, 2012, 5:37 PM
Post #3 of 4
(2270 views)
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Re: jeep 4.0 wont run
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really.we have checked al the vitals ,,,its has all ..it starts and then quits ,then will not restart ,when its tried ,its spits back threw the trottle plate ,like the timing is off ,but we know it not the motor ran great for a month
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