Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 10, 2025 ...

Lift pump noise on ISL400

February 13, 2012, 05:46:08 pm

Pat thinks we have a new noise coming from the engine.  I'm not sure it is new, but I have learned to listen to "dear wife" since she has much better hearing that I do.  At any rate, the humming noise from the engine comes on when I turn on the key, but before I start the engine.  It appears to be coming from the lift pump.  See pic below.  The pump will quit after a couple of minutes if the key is left on.

Questions......

1. If you own a coach with a ISL400, do you hear this noise when the ignition key is turned on?

2.  Could this have anything to do with a blocked fuel filter?  The coach starts and seems to have normal power.  The coach is full of fuel and we have not had any fuel issues in the past.  I did add some Lucas biocide a month or so ago. 

3.  If this needs to be fixed, would it be best to take it to a Cummins service center or would a reliable diesel shop be able to address this problem.  Believe it or not, there is not an authorized Cummins service center in Tucson.  The nearest one is Phoenix. 

Thanks in advance.

Quote Selected

Re: Lift pump noise on ISL400

Reply #1 – February 13, 2012, 05:53:20 pm

George,

I think that noise is the pump building fuel pressure and it stops (maybe 30 seconds) when the pressure is up.  My old pump did that and the new one I had installed a few days ago does same thing.  New one was needed because old one was leaking; that's what I'd keep a lookout for.

Mike
2003 U-295

Quote Selected

Re: Lift pump noise on ISL400

Reply #2 – February 13, 2012, 09:13:05 pm

The lift pump is operating like it was designed to do. When the fuel filters are changed that helps to prime the system.

Quote Selected

Re: Lift pump noise on ISL400

Reply #3 – February 13, 2012, 10:32:55 pm

Thanks guys!  Much appreciated.

George

Quote Selected