Originally Posted by ZoomZ

Try different gauge, and hot. Also note the FSM calls for 200 RPM for those numbers. Make sure you are on a power supply not just battery. I'm guessing 150 was taken cold. FSM calls for warmed "thoroughly" engine, Fuel depressurized/fuse out, all plugs out, ACCELERATOR PEDAL FULLY DEPRESSED, and fully charged battery (I'd use a power supply).

If you get low readings still, pour some engine oil into cylinder from plug hole. take readings again, If pressure increases, you have worn rings.



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