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Old 08-22-2012, 11:01 PM   #1
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New Crate engine, old CPS (camshaft position sensor)

Need some guidance. Just finished replacing my 2004 Wrangler engine with a new crate engine from gearheadengines. The very last item I have to install is the CPS (all I did was removed the bolt from old engine and put it in a ziplock bag, never even disconnected wire). I reviewed the Jeep repair manual regarding the CPS and it sounds like I need a special tool to get the resync process right (DRP scan tool?). Is this something a newbe can tackle, or should I get it over to a shop with someone that knows what they are doing? I don't have a DRP scan tool. I've got about a month of my weekends into getting the all back together and I don't want to screw it up now.

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Old 08-23-2012, 01:57 PM   #2
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I assume you mean the sensor & the oil pump drive housing & have a 4.0. (?)



You don’t really need the DRB. It will be more precise with the DRB but by most accounts the computer will compensate for slight differences in the actual setting. It is only for injector timing, not spark. If the manual you refer to is the FSM then it has a very detailed procedure for installing it using a toothpick & finding TDC when installing it in a “rebuilt” engine (rather then pulling & reinstalling it back in the same engine where the crankshaft hasn’t been turned). If you are off too much you will get the CEL & either reset it or then take it to a shop with the DRB (some independent shops have them or of course the dealer). If you don’t get a light you should be OK. If you don’t have the FSM go here for an online read only manual & pick TJ Unlimited to get the ’03-’06 version. You need the Ignition Control section.


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Old 08-23-2012, 03:14 PM   #3
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Originally Posted by RUBI 4 MY MRS View Post
It is only for injector timing, not spark.
Sequencing, not timing. Injection timing is based on CPS input.
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Old 08-23-2012, 04:27 PM   #4
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Stand corrected.
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Old 08-25-2012, 10:45 PM   #5
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Good explanation, Rubi...I checked with my local dealer and they said they would take care of the final adjustments with DRP tool for $100. I figure that is a small price to pay to make sure I get it right. I appreciate the feedback.
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Old 08-26-2012, 12:17 AM   #6
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It is up to you but if you don't get a CEL I don't think setting it with the DRB will improve anything but that's just my opinion. Those of us with '05 & '06s with the later OPDAs that have lack of lubrication issues & have done various mods to the OPDA to improve reliability have had to remove ours multiple times & most have just set it as close as possible & few if any that I know of have spent the $ on dealer DRB settings.
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Old 08-26-2012, 09:43 AM   #7
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It is up to you but if you don't get a CEL I don't think setting it with the DRB will improve anything but that's just my opinion.
Agreed. The camshaft position sensor input does not have to be terribly precise. All it does is solve cylinder 1-6 ambiguity for the PCM so that the injection sequence is correct. The early 4.0L engines (ie: Renix) actually had a failure mode which allowed the engine to run with no camshaft input. The PCM would "guess" whether cylinder 1 or 6 was in the intake cycle. When it guessed wrong, the engine would still run, just not all that well.
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Old 08-26-2012, 10:14 AM   #8
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Originally Posted by tangofox007 View Post
Agreed. The camshaft position sensor input does not have to be terribly precise. All it does is solve cylinder 1-6 ambiguity for the PCM so that the injection sequence is correct. The early 4.0L engines (ie: Renix) actually had a failure mode which allowed the engine to run with no camshaft input. The PCM would "guess" whether cylinder 1 or 6 was in the intake cycle. When it guessed wrong, the engine would still run, just not all that well.

So what I'm gatering is that he should put it back together and drive it. If it runs good and gets no lights, he's GTG?

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