Compression Test Procedure

[seapadrik]

Hey,

I am hoping to get this engine started this weekend and am wondering if I should just go ahead and check the compression.

I have never done this procedure and certainly don't own the test kit, although I am about to go buy one.

http://www.sears.com/shc/s/p_10153_12605_SPM74451017P?prdNo=12&blockNo=12&blockType=G12

I found an old thread Where Don stated:
"We consider 85 to 115 psi to be the normal compression range"

So thats good. Can you help a newbie out on the procedure ? The engine is currently mounted to a cart in the garage, And i am going to hook up the battery to test it this weekend.

Thanks

[msmith10]

I usually test the engine while its warm, as you'll get different readings hot and cold, but you may not want to run it that long on the cart. Your readings will be higher on a hot engine, but if it passes cold it will pass hot.
1. Make sure water intake is shut off so you don't fill exhaust system with water which will then enter the cylinders. You're not actually going to run the engine during the test so it won't need cooling.
2. Remove spark plugs. Cover holes with a rag.
3. Remove coil wire, disable fuel pump if electric (remove fuse or disconnect wire)
4. Open throttle to wide open and leave it there.
5. Screw tester into spark plug hole 1 and crank engine with starter for a few seconds. You'll see the pressure on the gauge go up in steps and max out. When it tops out, that's the reading. Repeat on other cylinders.
6. If the readings are low or vary more than about 10% from one cylinder to the next, add a tablespoon of motor oil through the spark plug hole of the low cylinder(s). If this increases the pressure significantly, it indicates worn rings or valve guides (the oil acts to seal the gap somewhat). If it doesn't change it's more likely a valve that's sticking or not closing all the way.

[seapadrik]

Thanks Mark for the steps, very detailed. I appreciate it.

Cheers