Generac — Check Compression
Testing & diagnosis · Engine cylinder
From a Generac service manual covering: GPS 12500, GPS 15000, GPS 17500. Check it applies to your exact model before use.
Applies to: Generac GPS 12500, Generac GPS 15000
Before you start
- Do not rotate engine with electric starter with spark plugs removed
Procedure
- Remove both spark plugs.
- Insert a compression gauge into either cylinder.
- Crank the engine until there is no further increase in pressure.
- Record the highest reading; repeat for the remaining cylinder.
- Difference between cylinders should not exceed 25 percent.
Tools required
- compression gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Normal compression approximately 150 psi
- Difference between cylinders should not exceed 25 percent
Source: Generac service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.