If you own a Duramax — especially an LML with the CP4 injection pump — adding a lift pump is one of the most important protection upgrades you can do. FASS and AirDog are the two dominant brands. Both work. Here’s how they compare.
WHY YOU NEED A LIFT PUMP
- The factory CP4 pump relies on fuel for internal lubrication
- US diesel has lower lubricity than European spec
- Adding a lift pump increases inlet pressure and adds additional fuel lubricity
- Also filtration — both FASS and AirDog separate water from fuel before it reaches the injectors
FASS TITANIUM SERIES
- FASS is widely considered the premium option
- Titanium series uses brushless motor — quieter and longer-lasting
- Flow rates from 95 GPH to 220 GPH — match to your power level
- Built-in filtration: particulate + water separator
- Mounting: frame-mounted, replaces OEM lift pump location on most Duramax applications
- Best for: high-power builds, daily drivers who want bulletproof protection
AIRDOG II-4G
- Strong alternative to FASS — similar filtration system
- Slightly lower price point for comparable flow rates
- Very popular on forums — proven on high-mileage trucks
- Easier mounting on some applications
- 100 GPH and 150 GPH versions fit most Duramax builds
WHAT SIZE DO YOU NEED?
- Stock to mild tune (under 500 hp): 95–100 GPH
- Compound turbos or big injectors (500–700 hp): 150 GPH
- Competition builds: 220 GPH+