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How to Make a Compression Test Gauge

by William Kinsey

A compression gauge is a pressure gauge used to check the compression level inside an internal combustion engine combustion chamber. These gauges are designed to be screwed into the spark plug hole of the cylinder head. Once screwed in, the engine is cranked. The ignition system is disabled at this point to prevent the engine from starting. This test is performed while the engine is being cranked and not while the engine is running. Building a compression gauge requires only a few parts.

Step 1

Take the compression gauge and screw it onto one end of the hydraulic hose. If the hose does not fit, check the hardware store for a coupling which will allow these two pieces to connect together properly. This connection needs to be airtight.

Step 2

Take an old spark plug to the hardware store and locate a male coupling that is the same size as the spark plug. If it is the same size, it will screw into the spark plug hole of the engine.

Take the male coupling and the other end of the hydraulic hose and locate a coupling that will connect these two pieces together. Once connected, use sealant to get an air tight seal. The compression gauge is now complete and ready to be tested.

Items you will need

  • 100 PSI pressure gauge
  • Hydraulic hose designed for high pressure
  • Hose couplings
  • Sealant

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