What would cause no compression in one cylinder - LS1TECH



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What would cause no compression in one cylinder

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Old 10-14-2002, 09:40 PM   #1
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Default What would cause no compression in one cylinder

I know a valve stuck open and I guess bad rings but what specificaly would hold a valve open or make rings go bad. I only threw a multiple misfire code and I don't hear any ticking or anything, but the dealer says no compression.
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Old 10-14-2002, 09:48 PM   #2
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Default Re: What would cause no compression in one cylinder

Burnt valve,broken valve, valve not seating,hole in piston generally anthing that lets air escape combustion chamber. They need to do a leak down & see what the problem is.
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Old 10-14-2002, 11:14 PM   #3
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Default Re: What would cause no compression in one cylinder

Don't forget bent valve... Most common reason a valve won't seal, especially on these engines. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Please don't ask how I know this! <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" />
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Old 10-14-2002, 11:40 PM   #4
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Default Re: What would cause no compression in one cylinder

Hole in the piston! What happened? Give us some details!!!!
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Old 10-15-2002, 08:04 AM   #5
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Default Re: What would cause no compression in one cylinder

Well I was just driving normal and the car started to run real rough but no backfires and no noise. Then the ses light started flashing. I pulled over and hooked up the autotap and one code was there, p0300 multiple missfires. I drove it the rest of the way home about 2 miles and I let it sit overnight. The next morning I turned it on and it was still running bad but no codes. I even had all 8 misfire windows up and not a cingle one. I checked all the sensors,wires and couldn't find anything wrong. I did find a plug for the wideband tuning was halfway out but it still ran the same after I screwed it in all the way. So off to the dealer. On the way there the ses light was flashing again but still no backfires or funny noises, dealer looked at it all day and says I have no compression in one cylinder. Today they are going to tear it apart to see whats broken.
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Old 10-15-2002, 08:52 AM   #6
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Default Re: What would cause no compression in one cylinder

Sounds like a broken valve spring to me. It's not pulling the valve closed and allowing the air to escape into the intake or header.
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Old 10-15-2002, 09:22 AM   #7
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Default Re: What would cause no compression in one cylinder

Well I think I do have 941's
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Old 10-15-2002, 10:39 AM   #8
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Default Re: What would cause no compression in one cylinder

i had similar symptooms when my compression ring on #7 broke. Eventually the piston came apart and destroyed the motor, hence the new 389. The quick diagnosis would be to pop the valve cover, back off the rockers so the valves can seat, pull plug, pump cylinder with air. have your dipstick out, TB uncovered. then while pumping air put your ear (use a piece of vac hose as a stethescope) at each the dipstick tube, T-body then at rear exhaust tips. you will hear a steady stream of air very easily. When i did this, the air pressure actually blew the dip stick out of the tube! i had a BIG hole in the piston!!
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Old 10-15-2002, 11:17 AM   #9
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Default Re: What would cause no compression in one cylinder

Probably a broken spring.

Black Magic, I edited your sig... You are not a paid advertiser, cannot advertise unless you contact me.
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Old 10-15-2002, 11:33 AM   #10
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Default Re: What would cause no compression in one cylinder

Ditto the spring theory. Just pull the valve cover...

Shane
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Old 10-15-2002, 12:57 PM   #11
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Default Re: What would cause no compression in one cylinder

Cylinder number 3 valve spring is broke. If I give them a new spring the total cost will be $265. I guess i have a cool dealer.
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Old 08-26-2011, 11:53 AM   #12
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How long can you drive around with a dead cylinder
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Old 08-26-2011, 12:03 PM   #13
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You should really make a new thread...this one you dug up has been dead for about 9 years!
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Old 08-26-2011, 09:26 PM   #14
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Holy Reborn Thread Batman!
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Old 08-26-2011, 09:47 PM   #15
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lmao! Where do people keep getting this 9 year old threads from
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Old 08-28-2011, 12:44 AM   #16
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Quote:
Originally Posted by Black Magic View Post
Don't forget bent valve... Most common reason a valve won't seal, especially on these engines.
Yeah because a bent valve seals better on a non LS based engine.
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