Qsb 5.9 – Lift pump problem?

[joethomas30]

Hi folks,
I’m wondering what are the symptoms of a bad lift pump. My qsb 5.9 is not starting. I changed Racors, on engine filter, position sensors, fuel pressure sensor, and fuel actuator. I primed the filter by running the lift pump until fuel came out of the two ports on top of the filter. Fuel rail is definitely getting fuel.

So it seems like the lift pump is working, but is it possible that it’s weak? Does the lift pump need to generate a certain amount of pressure before the cr pump starts working? Also, would a bad lift pump cause it to lose prime after an hour or so?

Topic

[joethomas30]

Thanks. Just curious, when you had the bad lift pump, you said it would run at low speed no problem. What happened at higher RPMs?

[David R Flamer]

Seems like all of the QSB Lift Pumps are going

We had a lift pump fail (of course port engine so on the outside) and it would create a 2265 alarm consistently.

The engine would start and run at low speed no problem. Most likely because the tank was full of fuel and flow was no problem. I am confident that low fuel level would have created a no start situation.

No issues since replacement of the lift pump.

[Tony Athens]

We use genuine Cummins.. Not sure how old years wise yours is, but supposedly about 10 years ago, things got better………………………………..

[eddie]

Is there a SMX lift pump upgrade available?

[Tony Athens]

That is the electric priming pump you hear. The CR pump is mechanically driven when the engine runs. Once the engine is running, the electric lift pump turns back on and runs all the time..

[joethomas30]

Thanks. Another question, when I turn the key to “on” and I hear a pump going for 60 seconds, is that the lift pump or the cr pump or both? If it’s the lift pump, does the cr pump only run during cranking/running? And does it require a certain fuel pressure from the lift pump before the cr pump activates?

[Tony Athens]

No start QSB 5.9

Tough question to answer without knowing some history of what was going to before it did not start.. Any “codes” ??

Plus, install a 0-30 PSI gauge on the on-engine filter so you can SEE what is happening…… As to the that particular lift pump, they have been far from stellar as to reliability……………………………Maybe just change it and see what happens..Maybe install and squeeze bulb–That really makes it easy.

[Author]

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