QSB 5.9 Fuel Lift Pump

[jimschilthuis]

I have a new to me QSB 5.9 380 HP, S/N 46867441.  In my short experience with it, when I turn the key on, I can hear (what I believe is) the fuel lift pump.  It runs for 10 seconds or so, then stops, at which time I start the engine.  Today, when I turn the key, the lift pump runs… but it continues for 30 seconds or more and then stops (I presume it has timed out).  If I turn the key off, wait a minute or two, and repeat… the same thing happens.  The engine starts fine, and seems to run ok (I’ve only idled in the slip today).  How long should the lift pump run prior to starting the engine, and should it stop on it’s own prior to starting?  Any assistance would be appreciated.  

 

 

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[Tony Athens]

The QSB 5.9 fuel system is , IMO a bastard  “Cummins” design, whereas the QSC and QSL are Bosch.. Both systems use the elec pump to do the initial prime or/fill a filter as you said,  The big difference is after start-up.. The QSB 5.9 needs the elec pump to run all the time.. Your fuel system has a built-in  low pressure  pump (90 psi-ish at the last change filter) .. Superior system.. The new 6,.7 went to Bosch.

[deraldlary]

Turning the key on and off to run the lift pump is how you fill the on-engine filter with fuel after doing a filter change.  At least that’s how it works on a QSC.  I’m guessing that the QSB works in the same way.  

[Tony Athens]

Seems like 30 seconds was always the number.  After start-up on a QSB 5.9, the pump runs continuously. 

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jimschilthuis

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