Factory in-tank lift pump or aftermarket external

[PhilW55]

I have 2004.5 cummins and it had not had the in-tank lift pump "upgrade", still has the lift pump attached to the filter canister. My fuel level sending unit has been going bad for a while and had not crapped out entirely (was reading low too early and I could only put in 17-20 gal of fuel at 1/4 tank). Now it reads completely empty. Since I have to drop tank to install the level sending unit just wondering if I should do the in-tank lift pump at same time. Or just do the sending unit and install a FASS or other higher performance (external) lift pump.

 

[chri5k]

What sort of mods do you have to your truck? If it is basically stock then an aftermarket lift pump will probably not result in any benefit other than lightening your wallet.

Auxiliary or higher volume lift pumps are usually for engines / fuel systems that have been modified to deliver more fuel to the engine. Stock lift pumps may not be able to keep up and the high pressure pump gets starved for fuel. This usually manifests itself in dropping high pressure fuel rail readings that drop at high RPM / load or power increases with RPM / load and then suddenly drops off.

 

[PhilW55]

Truck is stock. Main reason I was considering an external pump is ease of maintenance/not having to drop the tank if fuel pump had a problem. Maybe I should ask how reliable is the in tank fuel lift pump? The original lift pump on my truck lasted 175k miles, the replacement went about 5k and it had a lifetime warranty but I couldn't find the receipt so bought another one. Would be nice to have lift pump that pushes the fuel from the tank rather than pulling it.

 

[PhilW55]

Decided to just replace sending unit and keep external lift pump. May still get a FASS lift pump mounted on frame near tank.

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[WhiteExpress]

There are very real benefits for ALL trucks to run an air separator setup, not to mention putting the 2 filters a very convenient place to swap out / drain.

That being said, if you're planning on staying stock, Fleece makes a nice unit that is in-tank and comes with a new level sensor. It isn't as 'great' of a solution as a FASS or AirDog, but it is a clean simple solution and won't add much if any additional noise.