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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21474 Location: Oklahoma City
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Posted: Fri Dec 08, 2017 2:08 pm Post subject: Re: Zero Compression? |
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Wildthings wrote: |
WhirledTraveller wrote: |
5) Valve that doesn't close all the way. This could be caused by a really bad valve adjustment (i.e. someone did it very wrong) or by the valve being help up by a piece of carbon or something between the valve and the seat. |
I used to see this a lot back 30 years ago. The fuel that was available then would cause lots of carbon to build up in the intake port and when the engine sat for a long while the carbon would come loose and fall down on the intake valve. When an attempt was made to get the engine restarted the carbon would hold several of the valves open causing very limited compression. Even if one or two cylinder would fire, the engine might still not clear itself of carbon all that fast. It might take a couple of minutes to get all the cylinder on line. |
Its also really common that an engine that was running rich and parked.....can have the rings siezed in the lands from fuel varnish so they cannot pressurize on the topside and ecpand outward ro seal. Ray |
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Wildthings Samba Member
Joined: March 13, 2005 Posts: 50261
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Posted: Fri Dec 08, 2017 2:21 pm Post subject: Re: Zero Compression? |
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Goach2 wrote: |
Lots of good suggestions. I'm going to start with a good battery tomorrow. I like the idea of the air pressure in the cylinder to when valves should be closed. perhaps I'm not getting a good seal with the gauge too. I don't know how everyone gets it down under the shielding on 2 & 3, but I did it by feel
Abscate, I'm about 20 mins from the border. You're welcome anytime! |
Your gauge may just use standard pipe threads, so the piece that screws into the spark plug hole likely can easily be lengthened with stuff from your local hardware. |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Fri Dec 08, 2017 5:32 pm Post subject: Re: Zero Compression? |
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is this a screw in compression gauge with an O-ring, or a push and hold style with the rubber nipple? _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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Goach2 Samba Member
Joined: November 20, 2017 Posts: 518 Location: Niagara Region, Ontario
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Posted: Mon Dec 11, 2017 12:57 pm Post subject: Re: Zero Compression? |
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It's the screw in. I pulled a valve cover off to see if it looked like a stuck valve, but I can see all the springs moving in/out. I'm probably doing something wrong with the gauge... it's so hard to see inside of all the cooling tin! |
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williamM Samba Member
Joined: August 07, 2008 Posts: 4333 Location: southwest Arizona
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Posted: Sat Dec 16, 2017 7:34 am Post subject: Re: Zero Compression? |
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OK- time for an update. _________________ some days I get up and just sit and think. Some days I just sit.
opinion untempered by fact is ignorance.
Don't step in any! |
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Goach2 Samba Member
Joined: November 20, 2017 Posts: 518 Location: Niagara Region, Ontario
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Posted: Sat Dec 16, 2017 8:00 am Post subject: Re: Zero Compression? |
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Well, I've chalked the compression tests up to user error for now, and am continuing on with other repairs. One question I have is in regards to what you can see through the plug-hole. I can only see one valve opening in closing near the hole, is there any way to see the other one to confirm? All the springs are compressing and releasing, so I don't think any are stuck... |
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airschooled Air-Schooled
Joined: April 04, 2012 Posts: 12688 Location: on a bike ride somewhere
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Posted: Sat Dec 16, 2017 9:54 am Post subject: Re: Zero Compression? |
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If the engine is installed, I’ve only ever been able to see T4 intake valves through the plug holes. The plugs are at just a kooky enough angle to hide the exhaust valves.
Robbie _________________ Learn how your vintage VW works. And why it doesn't!
One-on-one tech help for your Volkswagen:
www.airschooled.com |
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Harleyelf Samba Member
Joined: April 23, 2009 Posts: 1572 Location: Appleton, WI
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Posted: Sat Dec 16, 2017 10:45 am Post subject: Re: Zero Compression? |
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Try the hippie-tech compression check: get four wine corks, put them in the spark plug holes, and have someone crank the engine over while you watch and listen to see which cylinders pop the cork out and which are weak. |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Sat Dec 16, 2017 11:08 am Post subject: Re: Zero Compression? |
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Quote: |
Well, I've chalked the compression tests up to user error for now |
did you finally get good compression numbers? _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin
Last edited by SGKent on Wed Dec 20, 2017 9:16 am; edited 1 time in total |
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Goach2 Samba Member
Joined: November 20, 2017 Posts: 518 Location: Niagara Region, Ontario
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Posted: Sat Dec 16, 2017 3:07 pm Post subject: Re: Zero Compression? |
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Not yet, if there wasn't so much engine tin I would be able to see if the rubber washer is seating on it... I'm leaning towards the cork-test. Good thing Christmas is coming with lots of wine! _________________ 1977 FI Westfalia |
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williamM Samba Member
Joined: August 07, 2008 Posts: 4333 Location: southwest Arizona
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Posted: Wed Dec 20, 2017 9:09 am Post subject: Re: Zero Compression? |
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I bought the harbor freight inspection camera and it really takes the guess work out- you should have some pretty serious scuff marks on cylinser walls if you have zero compression -- just a thought. _________________ some days I get up and just sit and think. Some days I just sit.
opinion untempered by fact is ignorance.
Don't step in any! |
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