How do you perform a wet/dry engine compression testing?

Question

When the rest of the cylinder compression are doing fine (i.e 7 cylinders are normal 1, 2, 3, 4, 5, 6, 7 are at 125 lbs of compression and 8 is around 75 lbs. of compression.) What usually causes low compression in one cylinder? how do you detect a low cylinder compression? And How do you perform a wet/dry compression testing? PLease help me. My teacher was talking about this but I kinda got confused.

Answer 1

Allright! Listen better in school! You'll need it someday!

It;s really simple. A dry test is just a normal pump up and read the pressure. A wet test is to add a bit of motor oil into the cylinder. Here's what this tells you;

If compression is low on two adjacent cylinders, you probably have a blown head gasket, or warped or cracked head. If it ps only one cylider as in your case, it is usually a burnt or warped valve. It could also be a problem with the valve train (lifter, rocker etc).. By adding a bit of oil for the "wet" test, you are helping to seal up leaking piston rings. It you have low "dry" readings, and higher "wet" readings, you are now suspecting worn rings!

Answer 2

Wet Compression Test

Answer 3

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RE:
How do you perform a wet/dry engine compression testing?
When the rest of the cylinder compression are doing fine (i.e 7 cylinders are normal 1, 2, 3, 4, 5, 6, 7 are at 125 lbs of compression and 8 is around 75 lbs. of compression.) What usually causes low compression in one cylinder? how do you detect a low cylinder compression? And How do you perform a...

Answer 4

a number of things are possible for one cylinder to have low compression but it is usually one of the obvious ones like worn rings. it could also be a hole in the piston, a crack either in piston or head, worn or bent valves, bent valve stem, seating problem etc. since the other cylinders have normal compression you can rule out certain problems such as low oil.

to test each cylinder remove one sparkplug at a time and screw in the tester where the spark plug goes. that will narrow down your search. the air will leak out of the cylinder eventually but it shows what the pressure is and how long it lasts. the important thing is not the amount but that all cylinders are similar. to do a wet test you put a small amount of oil into the cylinder and then see if compression improves. this would show worn out rings but not necessarily a crack in the head unless it was really wide

Answer 5

compression is compression regaurless of how the engine spins. compression is created by a combonation of good seating rings and the valves being closed as well as the obvious that the piston is going upward. most times we like to spay a light mist of oil in the cylinder when we compression test and you need it to come arround 5 times to that cylinder.

Answer 6

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The only possible way is to have the starter installed.