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HELP! Cam sensor/timing question


 
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BW Stewart
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Joined: 28 Dec 2006
Location: Central Florida

PostPosted: Thu Dec 28, 2006 10:41 am    Post subject: HELP! Cam sensor/timing question Reply with quote

My son-in-law has a 2000 GC. Last night it just died on him - like a fuel pump death. We towed it home and this morning gave it a once over.
We had good fuel pressure. However, he noticed the "cam sensor" was turned 45%. Let me explain. He called it a cam sensor - I am not so sure. It is located on the passenger side of the block. If it were an older engine I would say it is where the distributor was located. It stands off the block about 5" and has two wire attached. In trying to start the Jeep I noticed the timing was off. When he said it was 45% out, I loosened the bolt clamp and turned it the way I would a distributor to the position it should have been in. It started right up and ran smooth. Needless to say on the surface this was the problem last night. However, I am concerned he has bigger problems. Why did it turn in the first place?The bolt that holds the clamped in place was tight - not snugg but tight! If I am guessing right the oil pump is on the other end of the common shaft.
It seems like something would have to bind up to twist the sensor the way that it did.
Has anyone experience this problem before that you can give me some good counsel?

Thanks
Bruce
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ThePhantum
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Joined: 23 Jan 2004
Location: I knew it...I'm surrounded by Assholes!

PostPosted: Thu Dec 28, 2006 2:50 pm    Post subject: Reply with quote

Moved this to the Grand Cherokee Forum.

2000 and up has a distributorless ignition system, so it most likely is the cam sensor. I'm assuming that the sensor is keyed so that it only "fits" one way. If for some reason the hold down bolt was loose and allowed the sensor to turn, it's possible that the key also wedged it up against the clamp...making the bolt seem like it was tight.

Just a guess....
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BW Stewart
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Joined: 28 Dec 2006
Location: Central Florida

PostPosted: Fri Dec 29, 2006 8:22 pm    Post subject: Reply with quote

OK here's what the problem was for general knowledge.
It was the cam sensor. It has an aluminum casing with bronze bushing at both ends. A shaft runs through it with a gear that runs off the camshaft. The bottom end of the shaft mates with the oil pump and drives the oil pump. It looks just like a distributor housing and shaft assembly without the rotor and cap. The shaft is grooved to carry oil up the shaft to the bushing (a terrible design for long term reliablity). Apparently the grooves got clogged (they're only a few 1000s wide and deep) probably clogged with bushing material and varnish. It resulted in the shaft running dry, gaulding the shaft, and spinning the housing. When the cam sensor housing turned it took the engine timing so far out it stalled and wouldn't restart. It was about 3 hrs work and $60. till we were done. So file this FYI. Oh, the engine had oil changed every 3000 mile and only had 90,000 mile on it. THE END
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