Fuel Transfer Pump

[Keith Browning]

It's a 2011 F650 with dual tanks that do not equalize. The diagnostics are straight forward and everything tested good. My test results at the transfer pump are:

[*]VPWR =B+

[*]VREF (from alternator) - 7 volts

[*]ground circuit = a-okay!

[*]Left & Right level sensor resistance = appropriate for fuel level

The WSM says to replace the pump. I did but it seems to not have corrected the concern. The truck came in with both tanks full to the top (which annoyed me) so I had to drop the fuel levels to verify the concern and I also monitored the sender Resistances AS I emptied each tank - no glitches detected.

 

I know there are different modes of operation for this pump and sometimes a truck has to be run for some time before the pump actually moves fuel from one tank to the other. I am asking if what time frames anyone has noticed for this to happen and do you think if the right tank is full and the left tank is @ 1/4 would that throw the pump into thinking there is a fault and not transfer fuel?

[Alex Bruene]

In my experience, 8 times out of 10, I find it's a sending unit (I'm sure I've replaced way more left senders than right)... Once out of 10 it's an alternator, and once out of 10, it's a transfer pump... )When they're working right, I find the levels are very close to one another. I have seen people that fill only the left tank, and wonder why it doesn't transfer to the right tank... I once filled a right side tank full, while the left tank was nearly empty, and it did transfer.

[Keith Browning]

My experience is similar though I have never had to replace an alternator for this concern as of yet. I tested the senders and found no problem with them however I suspect there is an issue with the left side. If the truck returns I may just replace it regardless as it is the most likely cause... even if I can't prove it other than it fixes the concern.