false compression readings ? Help

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michaelounn

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I have a new pittsburgh comp tester from harbor freight. i'm not impressed. everything tests at 40 psi including my good running saws. do i need to return it or am i missing some trick
 
Had the same trouble with an Advance Auto tester. You probably already know, but your good saw should read around 150-160 psi. It takes about 5 good cranks to get a good reading, so keep that in mind as well. Sounds like a bad tester.
 
Had the same trouble with an Advance Auto tester. You probably already know, but your good saw should read around 150-160 psi. It takes about 5 good cranks to get a good reading, so keep that in mind as well. Sounds like a bad tester.
Dont stop at 5 pull till it stops rising it could take 15 with a long hose.
 
You may have also purchased an automotive compression tester that has the check valve at the gauge, and not at the tester end. Those types will tend to test lower on small engines.
 
I have a new pittsburgh comp tester from harbor freight. i'm not impressed. everything tests at 40 psi including my good running saws. do i need to return it or am i missing some trick
Its a gauge with a fitting, not an ACBM. If it isn't working correctly, its the cheap chinesium you hoped would enhance your toolbox. Take it back and buy a Matco, Snap-on, etc. Spend 20 bucks, once.
 
I purchased an Echo compression tester and have been very pleased with it. One testing detail that I have wondered about is should the throttle be wide open or at least partially open when cranking to build pressure? Service manuals for older outboard motors specify throttle wide open.
 
You need the schrader valve as close to the cylinder as possible, but the valve needs to be as weak as piss also. If you can get your hands on the older type of valve with the exposed spring snip off enough coils until the valve only just closes by spring pressure. The ones that SnapOn sell are like this too.
If you use a tyre valve you have to overcome significant pressure just to get to open the valve.
I saw readings go from heartbreaking to 150 psi plus after changing valves.
Any tester designated as being for small engines will have the correct type of valve.
 
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