95jeepgc
blooper tube
'95 zj 5.2L 4" RC lift 33X12.50x15
Posts: 10
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Post by 95jeepgc on Jun 26, 2012 17:28:04 GMT -5
So I did a rebuild on my 5.2l v8 in my grand Cherokee (new rings gaskets and seals, oil pump, o2 sensor, magnaflow cat, fuel filter, spark plugs and wires, valve stems seals and redid the valves) problem is now I dropped my motor in and its having a starting issue. It will turn over but the die within 5 seconds. I can keep it alive by feathering the throttle but it sounds horrible then dies. I can't get the rpm over 1200. It's very disappointing and I am out of ideas. Any help would be awesome. I feel like I keep going over the problem and not seeing it.
Let me know if you need more details.
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Post by Rock Dawg on Jun 26, 2012 18:03:39 GMT -5
What year is the jeep/motor 1995? I'm guessing it is not timed correctly. Most computer operated motors have something to unplug by the distributer before you time it, so the computer doesn't try to time it for you.
If it is not that, double check your spark plug wires if you have a distbutior and make sure you have them correct to your cam.
Any other symptoms? Does it smell rich (if so check sensor O2 again) , or backfire (timing).
Will it start fine, almost every time them die after 5 seconds? (If so I think I remember something about computer telling the fuel pump to shutting off after about 3 seconds if it finds no oil pressure to save the motor).
Hope some of this helps.
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95jeepgc
blooper tube
'95 zj 5.2L 4" RC lift 33X12.50x15
Posts: 10
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Post by 95jeepgc on Jun 26, 2012 22:38:03 GMT -5
Other symptoms it has its backfiring when I feather the pedal. It doesn't smell rich. But my IAC goes open and allows air through.
My distributor is a 2 piece distributor. The gear that meshes with the cam stays in the block. Therefore my dis. can only be off 180* but I checked it and it is set correctly. I even indexed it with a multimeter since it is all computer controlled.
I have oil pressure. During cranking or while it runs for a second my oil pressure goes between 50-60 I believe.
If I try to spray carb cleaner or starter fluid in the throttle body it backfires big time.
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95jeepgc
blooper tube
'95 zj 5.2L 4" RC lift 33X12.50x15
Posts: 10
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Post by 95jeepgc on Jun 26, 2012 23:39:08 GMT -5
And while it runs the rpm tach sits at zero. Figured this would be a hint to what's wrong.
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Post by blk01ram on Jun 27, 2012 1:56:48 GMT -5
Sounds like a timing issue to me. Make sure all the plug wires are correct with the direction the rotor spins. Seen it a few times where the wires were in the on correctly but for the wrong direction.
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95jeepgc
blooper tube
'95 zj 5.2L 4" RC lift 33X12.50x15
Posts: 10
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Post by 95jeepgc on Jun 27, 2012 9:39:12 GMT -5
Firing order has been triple checked a bunch of times. After researching all night I'm wondering if it could be my crank position sensor. Cause my timing is computer controlled and goes off of the ckp and cmp. Anybody know anything about the ckp going bad? I kinda want input before I go buy a $65 sensor and have it not fix the problem. Thanks.
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Post by Leeland on Jun 27, 2012 14:47:53 GMT -5
Sorry but every thing you described sounds 180 out. I've watched a SBF run 180 out and it does every thing you described with the exception of the tach, I did not look at that when it was running. As far as the sensor, most the time I've dealt with one the reluctor ring needs to be spinning a certain speed so you can check the voltage produced. Not sure if there's a static check you can do besides checking the air gap and it'll be specific to what your working on. And timing, from what I read you need a scan tool to set according to multiple threads on jeep forums. If I were you I'd flip it 180 and see what it does, if you've done that already then I dunno what else to say, it ain't here in front of me so.... Tach wise, do you know what drives it? Coil or crank/cam sensor? I guess it's some thing else to check but all your connections and make sure you didn't miss a ground.
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95jeepgc
blooper tube
'95 zj 5.2L 4" RC lift 33X12.50x15
Posts: 10
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Post by 95jeepgc on Jun 27, 2012 16:08:42 GMT -5
I tried 180 out and it backfired through the intake. So i have the timing right. My tach works just not when the jeep is idling. does anybody know what drives the tach?
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Post by Rock Dawg on Jun 27, 2012 16:11:55 GMT -5
Did you replace the cam as well? If so check the firing order on the cam card. It may be different...
Their is an old school way to see if your timing is correct. I'll see if I can explain it. 1. First pull the number 1 spark plug. 2. Have a friend tab over the motor with the key and put your finger in the spark plug hole. 3. You will feel the compression stroke as the piston gets close to the top with the valves shut. 4. Once it is really close, double check it with the vibrator dampener and timing marks to see that you are close to your lines (TDC) + what the book says you should be at. 5. Now that you know your piston is up and your valves are closed (compression stroke), then pull the distributer cap off and see where the rotor is pointing. It should be pointing to the number 1 spark plug wire. If it is not then you know it is timing and how to adjust it so the rotor is pointing to the correct plug. If it looks correct then it is NOT timing.
Hope it helps. I would offer to stop by and see if I can help but my life has been really stressful and hectic for quite a while now and I don’t see it changing any time soon…
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Post by Leeland on Jun 27, 2012 17:44:50 GMT -5
Another thing you could check is your grounds and connections, and how's the battery? You may have missed a little one some where. You kinda reminded me of when I had my alt stop charging, car ran like poop and also would not rev cause the ecu didn't have enough juice to run the injectors. Can't remember what my tach was doing but I think it was acting funny and I believe my battery was at 10.5-11 V. A bad ground or dirty connection could replicate that problem.
Rusty I was just thinking about the difference between HO and non HO, FIRING ORDER and dizzy direction lol
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Post by chevyboy89 on Jun 27, 2012 18:54:16 GMT -5
I am close by I can always swing by and take a look at it this weekend if you would like.
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95jeepgc
blooper tube
'95 zj 5.2L 4" RC lift 33X12.50x15
Posts: 10
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Post by 95jeepgc on Jun 27, 2012 19:42:22 GMT -5
I figured out what it was! It was a bent crank position sensor. Must of got bent when I reinstalled the motor. Anyways I installed a new one waited fifteen mins and she fired right up. Thanks for all the help guys.
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Post by Rock Dawg on Jun 27, 2012 23:37:44 GMT -5
I figured out what it was! It was a bent crank position sensor. Must of got bent when I reinstalled the motor. Anyways I installed a new one waited fifteen mins and she fired right up. Thanks for all the help guys. Great! I'm glad you got it fixed!
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Post by Leeland on Jun 28, 2012 4:16:21 GMT -5
Thats gotta make you happy. Good job.
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