When a Geo Underground runs poorly, tearing apart the engine to gape what happens inside is a parcel of laborious grind. Running a compression test on Everyone of the Geo Underground's cylinders (three or four depending on the engine dimensions) is a choice journey of checking for worn gone parts and draggy engine problems. A compression analysis is accelerated and requires further cramped skill or determinate Accoutrement.
Instructions
1. Lukewarm up the engine in the Geo Underground before doing the compression test. The battery will need to spin the engine several times so be sure that it is in good condition. An engine compression test on a cold engine will not give accurate results.
2. Rotate the engine by cranking the starter so that compression builds in that cylinder. Write down the compression number since you will use it later.4. Move on to the next spark plug hole and repeat this procedure for each of the cylinders, three or four depending on the engine size. Disable the ignition coil or disable the ignition system by pulling the coil wire.
3. Choose one of the spark plug holes and insert the compression tester. Shut down the engine once it's warm and remove all three spark plugs from the 1.0L engine. If the Geo Metro contains a 1.3L engine, there will be four spark plugs. This spark plug removal allows the starter to spin the engine freely.
Compare these numbers to the manufacturer specifications. An ideal compression ratio for either size engine in a Geo Metro is 9.5:1. The test readings should fall within 15 PSI of this number as well as 10 PSI of each other.
5. Repeat the test on any cylinders that have a low reading. Add a small amount of motor oil to the cylinder before performing the test again. If this causes the compression number to increase, the cylinder has worn walls or worn piston rings. If the number is the same, worn valves or worn valve seats are the problem.
