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Unread 07-11-2013, 08:05 PM   #1
GODZJLA
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1995 ZJ 
 
Join Date: Jul 2013
Posts: 8
I put a crate 4.7L Stroker in my 95 ZJ a few years ago and it has never ran right. It vibrates at 3,000 rpm, it runs lean and misses. My plugs are white and i burn up my cat about once a year.
It has 27lb Bosch fuel injectors and a new fuel pump. Fuel pressure is stable at 38psi even at high RPMs. I have listened to the injectors with a stethoscope and they are all opening.
I have checked the Cam Position Sensor and Crank Position Sensors with an oscilloscope. The two signals are strong but they are out of sync by 10 degrees. I know that the distributor is in correctly because if I move it by one tooth in either direction, it won't run. Besides, the distributor has 13 teeth which would be more like 27-28 degrees.
I have confirmed that the flywheel is on correctly by checking that the forth pules of the CKP sensor goes low at cylinder 1 tdc. Beside, it only goes on one way.
i have also confirmed the cam timing is correct by marking the lift duration on the lower pulley and comparing it to my original motor.
I have tried everything I can think of.
Has anyone ever heard of a cam having the Dist. drive gear cut 10* out of sync? I'm grasping at straws..


Last edited by GODZJLA; 07-11-2013 at 08:30 PM..
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Unread 07-11-2013, 10:15 PM   #2
psouza1943
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2005 TJ Wrangler 
 
Join Date: Sep 2006
Location: California
Posts: 79
My experience with crank shaft and cam shaft sensors is only with 2005 model years, but...on those jeep vehicles it is not uncommon for the engine to run poorly, or not at all with aftermarket sensors. The function of these sensors includes signal conditioning that extends the pulse width output at higher engine speeds. As an example, the Doorman sensor has been measured with a pulse width in excess of 75% wider than the factory OEM unit, which the computer will not tolerate. If your sensors are similar in function, this could easily amount to a 10 degree error if your computer triggers on the trailing edge of the pulse. As a last resort you might try replacing both sensors with genuine jeep part numbers, if they are not now.

Phil
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Unread 07-11-2013, 10:50 PM   #3
GODZJLA
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1995 ZJ 
 
Join Date: Jul 2013
Posts: 8
Thanks Phil, I'll look in to that, I think I will check the duration of the CPS while turning the engine by hand and see if I get a different result. I know what you mean after market sensors, I tried 3 different crank position sensor before I finally bought an OEM one to fix stalling problem I had.
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Unread 07-11-2013, 11:08 PM   #4
psouza1943
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2005 TJ Wrangler 
 
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Location: California
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I just completed an analysis and postmortem of a Doorman camshaft sensor that was DOA during a OPDA replacement. The signal out was a clean 5 volt square wave pulse that looked identical to the OEM sensor at low speed. At about 1000 RPM (2000 RPM engine speed) the pulse width of the Doorman began to lengthen well beyond the OEM used as a reference.

I mounted the complete OPDA (oil pump drive assy) on a small variable speed lathe and compared sensor outputs on an oscilloscope at various speeds. The pulse width differences were obvious and the only visible anomaly

Phil.
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Unread 07-11-2013, 11:17 PM   #5
GODZJLA
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Interesting! Defiantly going to check that out!

Thanks again
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Unread 07-12-2013, 09:45 AM   #6
RWKHausSupply
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1990 XJ Cherokee 
 
Join Date: Nov 2009
Location: Yorba Linda
Posts: 208
I have a 4.7+ ish.

I run a 24lbs inj at 49psi.

I have 10.5-11:1 comp. Nice custom cam. and Lots of head work with larger valves etc...

You might do better getting a quality 24lbs inj, and doing a aftermarket quality ext pump, and bypass regulator set at a higher PSI. You get a better atomization of the fuel which will burn much better and thoroughly. Not to mention you can up the amount of fuel into the cylinder with just a turn of a set screw.
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Unread 07-13-2013, 10:24 AM   #7
GODZJLA
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Thanks, you are right, I have 24lb Bosch injectors. Not 27lb. Could you recommend a pump
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Unread 07-13-2013, 03:15 PM   #8
RWKHausSupply
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Bosch I think its a e2000
And a bypass style adjustable regulator. Any brand.
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