1995 Geo Prizm Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Mechanical Inspection: Compression

  1. Check engine mechanical condition using a compression gauge, vacuum gauge or engine analyzer. See engine analyzer manual for specific instructions. See COMPRESSION SPECIFICATIONS table below.
  2. Start engine and allow it to reach normal operating temperature. Turn ignition to LOCK position. Remove all spark plug plugs. Disconnect secondary ignition wire from coil.
  3. Install compression gauge. Disengage clutch on manual transaxle equipped vehicles to reduce drag on engine. Fully depress accelerator pedal to Wide-Open Throttle (WOT) position. Using a fully charged battery, crank engine to specified RPM. See COMPRESSION SPECIFICATIONS table. On each cylinder, the highest of 4 compression gauge readings is considered the compression pressure.
COMPRESSION SPECIFICATIONS

Application Specification
Compression Ratio 9.5:1
Normal Compression Pressure (1) 191 psi (13.4 kg/cm2 )
Minimum Compression Pressure (1) 142 psi (10.0 kg/cm2 )
Maximum Variation Between Cylinders 14 psi (1.0 kg/cm2 )
(1) Checked at 250 RPM.
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

Shop Manual-Ready ToolsCompare Repair QuoteQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.