Generac — Test 36 – Cylinder Leak Down / Compression Test
Testing & diagnosis · Engine cylinder sealing
From a Generac service manual covering: GP1800, GP1850, GP3250, GP5000, GP5500, GP6500, GP7000, GP8000. Check it applies to your exact model before use.
Applies to: Generac GP1800, Generac GP3250, Generac GP5000, Generac GP5500, Generac GP6500, Generac GP7000, Generac GP8000, Generac OHVI engine
Procedure
- Remove the spark plug.
- Gain access to the flywheel and remove the valve cover.
- Rotate crankshaft until piston reaches TDC (both valves closed).
- Lock the flywheel at top dead center.
- Attach leak down tester adapter to spark plug hole.
- Connect an air source of at least 90 psi.
- Adjust regulated pressure to 80 psi.
- Read right hand gauge; 20 percent leakage is normally acceptable.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Minimum allowable compression pressure cold engine 60 psi
- 80 psi regulated pressure
- 20 percent leakage acceptable
Full service-parts list: Generac GP1800 →, Generac GP3250 →, Generac GP5000 →, Generac GP5500 →, Generac GP6500 →, Generac GP7000 →, Generac GP8000 →
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.