I have a 6 cylinder 200 cu in engine and I want to check the compression of each cylinder. I have a Chilton manual but the information under engine specifications is Greek to me, but I CAN read a compression tester gauge. What's the acceptable compression range for this engine? To my knowledge it's never been rebuilt or overhauled, but I don't know that for sure.

Also, when you do the test do you remove all the spark plugs at once, or one by one as you test the cylinders?

Please make your answer dummy proof...

Thanks............

 

- warm up engine
- remove _all_ spark plugs (this way you put less strain on battery, as the other - cylinders will have no compression while testing)
- remove all cables going to coil- (at coil-) so you don't produce any sparks.
- check one cylinder after another
- stay away from push on compression tester, screw in type is the way to go
- when testing make sure to floor the throttle to allow as much air as possible into cylinder
- crank each cylinder for at least 5 compression strokes. write down the pressure after 2-3 stroke and max pressure. stop cranking if pressure doesn't increase and note how many turns it took. 3? 5?
- if a cylinder is lower on compression than any of the others, redo that cylinder but add a teaspoon of oil into the cylinder (through spark plug hole).

all cylinders should be in the same 10% of each other
If compression rises when you do a wet test (with the oil), then the culprit is piston rings
if you have 2 cylinders next to each other low, the most likely cause is headgasket

that's probably the important info ...

 

You want to remove all of the plugs for the test. You don't want any unnecessary load while you do it. (just the load of the one you are testing) You also want to stuff something (like a screwdriver) into the carb to hold the throttle plate open. This allows for maximum air to enter. One more thing is to disable the ignition. Take the coil wire running to the dist and ground it.

For an old motor, I would expect to see around 120psi. Don't worry too much if you are off of that though. What you really want to see is that all 6 are similar. Within 5% from highest to lowest. So, if you have some that are 115 and some are 125, that's not really a problem. However if you have most at 130 and 1 or 2 at 60...then you have a problem.

 

Remove all spark plugs from the engine,use something to hold the carb wide open during the test.Crank engine with tester in each cylinder and only crank engine for a total of 5 hits on the gauge, cranking it more does nothing for the test, just kills the battery.Write the psi down for each cylinder and from highest to lowest it should not be more than 10 percent different.If the engine otherwise good running condition you can use a can Engine Restorer with each oil change and it will even out the cylinder pressures. Skeptical, I know, I tried in my 89 Taurus and it worked great.