cyberz350

iTrader: (3)

Hey guys, how do I do a compression test. I know there is a tool for it but I was wondering what the procedure was. I read that I had to disable the fuel pump and the ignition so that it wouldn't spray fuel or turn over. How do I do that? Is there anything else involved? Thanks guys.

westpak

iTrader: (19)

You can get a compression test kit at any parts store, around 50 bucks, it tests one cylinder at a time, you run the engine for a few minutes then **** it down and remove all spark plugs, back out the plugs a little and then remove one at a time install the tester and crank the engine through 4 cycles and you should get a pressure reading on the gage thta comes with the kit, repeat for each cylinder.

This gives a snapshot of the compression of each cylinder, another test that would tell you more is a leak down check which tells you how well the cyclinder is holding that pressure and not letting it pass.

Q45tech

Make sure the throttle plate is held wide open and battery charger bridged to make sure starter rpm is constant..........bit more to it if accurate numbers are desired. Need a electronic digital compression gauge to be precise.

Google is yor friend!

cyberz350

iTrader: (3)

Well, I remembered I had the manual so I looked it up and figured out how to do it. The thing is I didn't have a engine tachometer so I just did it without pusing down on the accelerator. Would that make it inaccurate? I basically just cranked the engine till the needle stopped climbing and they were all around 190. Was I wrong in doing this?


CHECKING COMPRESSION PRESSURE
1. Warm up engine thoroughly. Then, stop it.
2. Release fuel pressure. Refer to EC-53, "FUEL PRESSURE RELEASE" .
3. Disconnect fuel pump fuse to avoid fuel injection during measurement.
4. Remove engine cover with power tool. Refer to EM-17, "INTAKE
MANIFOLD COLLECTOR" .
5. Remove ignition coil and spark plug from each cylinder.
Refer to EM-30, "IGNITION COIL" and EM-31, "SPARK PLUG
(PLATINUM-TIPPED TYPE)" .
6. Connect engine tachometer (not required in use of CONSULTll).
7. Install compression tester with adapter onto spark plug hole.

Use compression gauge whose picking up end inserted to spark
plug hole is smaller than 20 mm (0.79 in) in diameter. Otherwise,
it may be caught by cylinder head during removal.
8. With accelerator pedal fully depressed, turn ignition switch to
“START” for cranking. When the gauge pointer stabilizes, read
the compression pressure and engine rpm. Perform these steps
to check each cylinder.
Unit: kPa (kg/cm2 , psi) /rpm
CAUTION:
Always use a fully changed battery to obtain specified engine speed.

If the engine speed is out of specified range, check battery liquid for proper gravity. Check engine speed
again with normal battery gravity.

If compression pressure is below minimum value, check valve clearances and parts associated with combustion
chamber (valve, valve seat, piston, piston ring, cylinder bore, cylinder head, cylinder head gasket).
After the checking, measure compression pressure again.

If some cylinders have low compression pressure, pour small amount of engine oil into the spark plug hole
of the cylinder to re-check it for compression.
– If the added engine oil improves the compression, the piston rings may be worn out or damaged. Check
the piston rings and replace if necessary.
– If the compression pressure remains at low level despite the addition of engine oil, the valves may be malfunctioning.
Check the valves for damage. Replace the valve or valve seat accordingly.