i want/need to check my compression and have a compression tester but no instructions...........do i just go to each cylinder with it? also do i need to start the car and keep it running for a certian amount of time and what should my compression be at for a 166xxx miles 305TPI???

thanks guys

 

here it is

 

Take all your plugs out; disconnect power to the distributor; block the throttle wide open; and put it in a cylinder. Have somebody crank the motor with the starter. Watch the gauge; you'll see it go up in pulses; after about 4 or 5 pulses it'll stop going up; that's the number you want. Record it, then push the little button to let the pressure out, hook it up to the next cyl, and repeat.

I don't see a hose or fittings, you'll need those.

 

or,,,,As for the compression test, you first run all the cylinders in the normal fashion (all plugs out, coil disabled, choke and throttle held full open, crank each cylinder until max pressure reached, record each cylinder's pressure, etc.). That's the dry test. Then, you put a tablespoon or so of oil in the cylinders through the spark plug holes, turn the engine over a few times to spread it around the cylinder, and then repeat the compression test. If the rings are worn, the oil will tend to enhance the seal and raise the compression pressure significantly from the dry test. You have to do both in order for the wet test to have any meaning. If the dry test numbers are close cylinder-to-cylinder and where they should be (say 150 psi), and no significant change to the dry test, then everything's fine. If the dry test is low and the wet test is low, then you have valve sealing problems.

Per 5-7kid

 

very very sweet guys.........i really didnt know what the heck to do but now i think i got it!

thanks

 

whatever numbers you get don't mean as much as the deviation between numbers. you'd like to have all the readings to be within 10%.

 

Was searchinmg and came accross this.

I've always done one at a time (leaving the remaining plugs in) and replaing the plug after each tested cyl.

What do you think the differences are between the way I did it, and the way you proposed ?

And the reason I searched this, is because after about 20 1/4 passes, my car has a horrid skip now. Think I broke something

-- Joe

 

If you leave the other plugs in, all you accomplish, is to make it harder for the starter to turn the motor over; which introduces an element of incosistency to the results. That's why you're supposed to take all the plugs out, and why it's wrong to do it that way.

 

Thats interesting, and I'll try it this way tonight.

Do you think there would be a considerable difference in the psi between tests? Unfortunately, I have a log book of test results with the other method, so if I do a test tonight i'd like to know if my results differ because of a mechanical problem, or because of a difference in testing method?

-- Joe

 

No way to know, too many variables.... that's why there's one right way and any number of wrong ways.