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Old 04-03-2012, 11:11 PM
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WJ GC V8 woes

Hi All, Thanks for the site. I'm sure it'll come in handy.
That was how I was going to start off as a new member of the Jeep Garage. Alas, it was not to be.
I recently purchased a '2000 WJ GC V8 that ran beautifully for the first 2 months. Then the unthinkable happened while out shopping.
It started with a tick-tick-tick that progressively got louder and quickly changed to a knocking noise when all of a sudden the gauges started flickering wildly and it stalled. I tried to restart it but all it would do was turn over and not fire.
After leaving it sit for 5 minutes I tried again. It started to fire up and a huge cloud of black smoke erupted from the exhaust pipe. It wasn't running rough, but didn't seem to have a lot of power and all the gauges were operating correctly.
I managed to get it the 2km to home where it died again and, this time, wouldn't restart.
Checked for any error codes using the key dance and my OBD code reader and there were none.
Now the worst part. Pulled the spark plugs out and they all had huge (1.6mm+) gaps and were very worn.
Compression test showed most cylinders had 0-30psi and 2 had 110psi.
Put some oil into the cylinders and retried. The pressures rose up to 30 psi minimum.
I had initially suspected the Crank Position Sensor to have failed, but can't justify that with no compression.

I also had a huge power drain that flattened the battery completely.

Has anyone got any ideas - apart from rebuild/replace the engine?
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Old 04-03-2012, 11:30 PM
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Re: WJ GC V8 woes

I suspect oil flow related.
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Old 04-03-2012, 11:52 PM
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Re: WJ GC V8 woes

Ok, checked that again. The oil pressure just on cranking it is over 3 Bar.
Pulled the LH rocker cover off to check the valve train. Pretty dirty and grubby but nothing loose or damaged and the chain wasn't loose.
Tom
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Old 04-04-2012, 02:56 AM
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Re: WJ GC V8 woes

try rolling the motor over to 0 lift on the valves (when your on the base circle on the cam lobe) then try to move the rocker. I just had a WJ 4.7l in that dropped and intake valve seat on cylinder 2 last week. Beyond my 100% leakage out of my intake with the valve cover off I touched the rocker and it all but fell out of place (indicating the valve was being held open). There should be some tension holding all the rockers in when they are at 0 lift. This engine was making all kinds of knocking and clattering noises and no check engine lamp other than a stored injector DTC and it ran like a bag of asses. When it stalled out (while I was taking it up to my stall) it was difficult to restart but did eventually. My assumption is the one completely failed cylinder was causing big problems with the entire fuel system, pumping fuel filled air back up into the intake and raw fuel and air into the exhaust throwing off the fuel trim for the other cylinders on that bank. Your compression does not sound good though, that sounds mechanical, 30psi is VERY low (you clearly know that) and unfourtunatly there is going to be no easy way to restore compression, a leakdown test would be great but ultimately the motor is very likely going to need to come apart for further inspection.

Ive seen the slides get damaged, never actually fall out and/or fail but I have removed and replaced damaged chain slides.

Did the knocking continue after you got it restarted?

Sorry for your troubles, welcome to the forum though!
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Old 04-04-2012, 07:45 PM
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Re: WJ GC V8 woes

I did take the LH rocker cover off for a look at the valve gear and chain but they looked ok and tight. I was initially thinking that the chain had slipped and was opening valves when they should be closed - hence bugga all compression.
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Old 04-05-2012, 05:28 AM
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Re: WJ GC V8 woes

Here's the latest thoughts before I rip this thing out and strip it.
As the compression is low in all cylinders, whats the likelihood of a failed camshaft timing gear - and is it a possibility, or are they a fibre compound that could fail.
This seems possible as ALL cylinders are low in compression, though I'm not totally convinced yet. It did restart again!!
But that could have been the final gasp.
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Old 04-05-2012, 05:43 AM
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You can see the cams with the valve covers off.

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Old 04-05-2012, 07:00 PM
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Re: WJ GC V8 woes

The valves are still operating as I can see them thru the sparkplug hole when I turn the engine over, so I think I'll have to check the crank/cam timing.
Are the ignition timing marks - or TDC mark - easily visible as i can't find it.
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Old 04-05-2012, 07:28 PM
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Each cam gear has a V8 on them and at TDC #1 cylinder they will be in the 12 o'clock position I'd the timing is correct. You'll need to pull both cam covers to check this. There is also a grove in the harmonic balancer and a few marks on the timing cover but they are hard to see.

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Old 04-06-2012, 01:00 AM
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Re: WJ GC V8 woes

Many thanks for that. Found the marks eventually. Just gotta wait til tomorrow to get back into it.
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Old 04-07-2012, 01:29 AM
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Re: WJ GC V8 woes

Hi again. Latest update on my 'No compression' proble isn't good news I'm afraid.
A leakdown check showed almost 100% leakage - into the cooling system.
So now I'm looking at heads/gaskets/block issues.
The timing was spot on.
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Old 04-07-2012, 06:51 AM
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Could be a simple as needing a head gasket. Need to have heads checked for warpage regardless.

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