Checking engine compression

[rdengil1]

I checked my engine compression after I have been having trouble getting the my engine to start. Engine is an AQ131D. The compression checked accross all 4 cylinders was 130 on all four consistently. I checked by removing all plugs and the ignition coil wire ensured the timing marks lined up and the turned the engine over through several revolutions. the readings stayed the same throughout. My question is should the compression hold at the point where I stop the engine? Meaning if I just tap the key and the compression goes up to 130 and I stop, should it remain at 130? It isn't on mine, just drops back to 0 when I stop turning the key. Just want to know if this is normal. Thanks.

 

[RicardoMarine]

The gauge system contains a check valve. This means that the gauge should hold the reading even after you quick cranking.
It will read an accumulated pressure from three/four cycles, and the reading will eventually stop increasing.
The first compression cycle has to also pressurize the hose and gauge.
The next cycle begins to show accurate cylinder pressure.
The third/forth cycles are to ensure max pressure reading has been seen by the gauge.
Do a minimum of three/four cycles..... do five if you like.
IOW, you could turn it over ten times, and still have the correct reading.
This is normal.


Next time when you run a comp test, disable the power lead to the coil.
The coil saturation and field collapse causes high voltage on the secondary side, and this needs to have a path to negative!
If you do not give it a path, the coil can become damaged upon excessive cycles.

 

[rdengil1]

thanks. The compression was good, actually got it to fire today. but still have a few issues to work with regard to the timing. See the other post. Appreciate all the help. Just wish I had someone here that wasn't to expensive to come and fix this thing.