99 Grand Cherokee timing problems - JeepForum.com
 
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post #1 of 11 Old 10-21-2021, 01:27 PM Thread Starter
purplesmiles
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99 Grand Cherokee timing problems

Hello,

My sister owns a 1999 Jeep Grand Cherokee 4.0L l6. We have had to replace the motor in it. When we replaced the motor, we replaced a lot of the parts on the used motor that we were putting in it, including water pump, oil pump, and timing chain. This was our first time timing a Jeep (we have done 2 Ford 5.4Ls in the past year without issue). We followed the diagrams I could find and lined the timing marks up directly across from each other and in a straight line with the centers of the gears/sprockets. The problem is that she won't start. She will backfire through the exhaust. When you turn the crankshaft 2 rotations, the timing marks do not line back up. The timing mark on the cam side is off by 180 degrees (in the roughly 11pm position). We have timed it about 5 times now and it does it every time. We made sure that #1 was on TDC each time but can't seem to figure out why it is doing this. Any insight is appreciated as we need this vehicle back on the road and this is our biggest obstacle to getting that done. I think I provided all the information but if I missed something let me know and I will answer the best I can. I am somewhat well versed in mechanics but there is still a lot that I don't know

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post #2 of 11 Old 10-21-2021, 06:24 PM
Ntrenn
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If you keep turning it over, do the marks come back into alignment? Some chain designs have the chain walk on the sprockets…Nissan 3.5s do that. Evens out the wear. Usually won’t start comes from missing the tooth alignment on a distributor.. service manual shows crankshaft keyway at 12:00 and the camshaft keyway at 3:00 when the timing marks are aligned. Your woodruff keys are intact, right?
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post #3 of 11 Old 10-21-2021, 11:55 PM
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post #4 of 11 Old 10-25-2021, 07:10 AM Thread Starter
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Thanks. I will look at all of this soon. I work full-time and my dad can't read so it will take us a little bit to get back to seeing if any of this will work.
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post #5 of 11 Old 10-25-2021, 08:01 AM
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youu did not remove engine, and had no problem with CKP before repairs?
As it is cranking - are there any codes being set?

An OEM cam timing alignment diagram is attached, picture =1000 words.

You did purchase a timing set* and sometimes the manufacturer has a diagram included esp if they mark it differently than OEM very rare but I have to mention. Also changed as a set all 3 replaced?

The CMP - did you check alignment - remember engine at TDC on #1 COMPRESSION.

*packaged gear and chain.
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When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #6 of 11 Old 10-25-2021, 10:26 AM Thread Starter
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We removed the engine out of one jeep and replaced a bunch of parts on it and put it in my sister's jeep. We have even switched the crankshaft sensor and camshaft sensor from her old engine to the "new" one (after it wouldn't start initially so they thought they should change the sensors since they knew that the ones in the other engine worked). The old engine started and ran but had busted the block (they drove it into the garage so all was well with it starting before the breakdown). I cannot answer about codes right now. I wasn't the one trying to start it but I will check and get back to you. That picture is the exact alignment we have used to time it. We did replace all 3 pieces (both gears and the chain). We did not see a diagram with any new instructions for timing it when replacing it in the box it came in. Engine was at TDC when #1 was on compression (I forgot to mention the compression part). I have to check the alignment on the sensors because I didn't install them. That is on my list to try when we can get back to it.
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post #7 of 11 Old 10-25-2021, 11:35 AM
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ok glad you added that info, something to consider - swapping engines, changing sensors.

That might be the problem, what year jeeps were involved - the donor and the recipient.

I am thinking you did NOT swap flywheel/flexplate, Different years used different 'tone rings' .

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #8 of 11 Old 10-26-2021, 10:06 AM Thread Starter
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All vehicles involved are 1999 Jeep Grand Cherokee Laredos. We didn't change the sensors until it wouldn't start initially. Changing the sensors was part of trying to fix it not starting (they thought maybe one of the sensors was bad so took it off the old engine to try it on the new one to see if it would start then). Then we swapped with the sensors we knew were working because we had just had that engine running. As far as I know, the flywheel/flex plate was not changed but I wasn't in the garage for the whole thing so I can't be 100% sure.
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post #9 of 11 Old 10-26-2021, 04:52 PM
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I would suggest a few basic things to check. Are the spark plugs getting wet? Is it firing? How is the compression?
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post #10 of 11 Old 10-27-2021, 11:06 AM
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If you had the crank sensor out, did you set the air gap with the paper spacers? It’s Jeep’s way of a ckp relearn.
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post #11 of 11 Old 11-02-2021, 10:55 AM Thread Starter
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Quote:
Originally Posted by rep-tile View Post
This fixed the timing issue. We still don't have it running but it is trying. We think we have a fuel issue now (possibly not getting enough fuel pressure/old gas)
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