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-   -   Jeez...Iwas hoping this wasn't the problem (http://forums.pelicanparts.com/porsche-911-technical-forum/92686-jeez-iwas-hoping-wasnt-problem.html)

speedo 01-01-2003 01:48 PM

Jeez...Iwas hoping this wasn't the problem
 
These are great engines...they will run on 5 cylinders eh? Number 5 shows barely any compression...the others1-2-3 show between 105 and 110 psi. Number 4 shows 103 and 6 shows 95 psi. The big question is...if a cylinder shows almost no compression ( versus low 60-80 psi), does this tell me that it's not a ring problem , and since it doesn't sound like metal inside the cylinder that it's probably not a hole in the piston, but since it does burn oil ...bluish-white...that maybe we're talking a stuck valve or broken spring on the exhaust? While doing the compression check I had all the plugs pulled to check their gaps and as I worked from 1-6 ....there was a "popping" sound out of the 5 plug hole. Do I drop it and tear into it or can it be dealt with from the top side?

john walker's workshop 01-01-2003 02:35 PM

no valve clearance, or a valve that's being held open by an improper adjustment will cause low, or no compression. pull the covers first and run thru the firing order and just see if you can feel some clearance on all rockers with your fingers moving the rocker back and forth. no need to use a feeler gauge for this quick diagnosis. otherwise it seems like it needs at least a valve grind because the other cylinders should pump more than that, not to mention the dead hole. when the heads are off, pull off the cylinders and inspect the pistons and rings. you may have a piston that's burned down the side thru all the rings. that would cause no compression and smoking of course.
modify your profile so the year of your car and your name appear as a signature. it's helpful to have the car info for accurate answers and names are nice too.

speedo 01-01-2003 02:50 PM

Thanks John...profile update being done. This motor 73 2.4 T has webers and has been sitting. New project to me. After sorting through electrical problems, I got it to run...roughly. I was hoping it was distributor related. I had to modify a borrowed compression tester and I'm not sure how accurate it was/is. I was at least pleased that the other 5 jugs were close in their numbers. Remember I checked the compression by pulling all plugs and turning the motor over using the starter with the throttle open full. Would this give me different readings than if the motor was running? I don't have much history on the car other than a local shop confirmed performing a non-eventful tune up on the car 4 years ago. The weber install looks professional. Could sitting for that long cause...someting to..stick?

Rot 911 01-01-2003 02:56 PM

Do what John says and then make sure you do your compression test with the engine warm.

dean 01-01-2003 05:48 PM

Do a leakdown test

john walker's workshop 01-02-2003 07:59 AM

it is hard to get a true compression reading on a cold engine with "dry" rings. one that's been sitting for a while often gets carbon bits between the valve and piston which cause low comp readings and high leakdown readings. (from carbon falling off the piston and combustion chamber. it tends to flake off). concentrate on the dead hole and see what shows up. if you don't feel any clearance, create some and check the compression again.

speedo 01-03-2003 10:20 AM

John, I forgot to mention that I'm at 8100 ft and based on Waynes altitude approximations...that should put me right where I need to be for thre other 5 jugs...140 psi x .79 = 110 psi. Is this correct? I'm about to drain the oil and pull the covers to see what I find, and then drop it and proceed with the necessary fix. If I can get my hands on the tools, I'd like to try a leak-down too.


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