F250 dies after 10 minutes if fuel bulb not pumped

[jol1ymon]

2006 LF250TUR will sputter and die if the fuel bulb is not pumped every 10 minutes or so. I replaced the low pressure pump 2 months ago, which rotted due to water in the fuel system. Since then tank has been drained, and refilled with Rec 90. Fuel Pickup inspected and cleaned. Anti Siphon valve inspected and cleaned, new fuel lines from tank to new racor, new fuel lines to motor, including new bulb. Cleaned filter on front of motor, T-Shaped Filter and installed new High Pressure pump and cleaned its filter. VST tank spotless when it went back in. Pulled fuel rails and cleaned them out, cleaned injectors, and fuel lines that feed the fuel rails. Motor runs perfectly as long as bulb is pumped. No longer water in system..have drained VST and filters multiple times...all good fuel. Checked all of the fuses on the Starboard side, all good. Checked all of the Relays that run the fuel pumps on same side just below fuses, they are in spec with Yamaha manual. My thought was maybe the "new" low pressure pump does not work. Jump it on 12 volts and it spins just fine. Not sure where to go next. Is it possible that the low pressure pump spins, but the impeller or whatever moves the fuel is not moving? Just spinning on the shaft that drives it? I am out of ideas. Help is greatly appreciated!!!

[DennisG01]

Not being overly familiar with your LP pump, but am generally familiar with pumps overall... when it's running, you may be able to feel it running by putting your hand on it. Can you verify that?

Try running the boat with the fuel cap off... you may have something as simple as a blocked vent.

[fairdeal]

so the lift pump is not keeping the VST full -
you need to find out why....
is the pump itself to blame? or is something else handicapping it...

as Dennis suggests - might be a restriction on the suction side
so for that you Tee a vacuum gauge in, and see what the pump is "pulling"

or you can start with Tee-ing in a pressure gauge on the outlet side -
see if the pump is making and maintaining >10 psi to the VST inlet
if not - it may or may not be "running"

to see whether the pump is being electrically energized-
you can patch in an LED to the ground side of the pump

(if I'm looking at the right diagram, the pump always has power with key on -
but gets its ground from the ECM)


btw if you like just throwing parts -
seems you haven't mentioned the "relief valve" on the LP pump outlet
if that is "stuck open" -
could cause the LP pump to "chase its tail" rather than fill the VST

[jol1ymon]

I will check the relief valve. Appreciate the input. All of the parts that I installed was due to water in the fuel. It caused both fuel pumps to corrode, from sitting in the fuel/water mixture. There is a possibility that there may be debris in that valve...have not checked there, found debris elsewhere in fuel system, so makes sense. When I added the racor (rather than just the water separating filter) I relocated it out of the bilge to a compartment on the transom, just above the deck, so I can monitor and check for water in the fuel now. This is why I replaced all of the fuel lines to re-plumb the fuel system.

[99yam40]

to see whether the pump is being electrically energized-
you can patch in an LED to the ground side of the pump

interesting , where would you tie the other leg of the LED?
to ground so that when the ECU does not provide the ground path, the LED would light up because of the open ground side would be 12V+.

what type of LED would you have to find to do this?
a volt meter may be easier to find and use.

My guess is this would be just for testing and then removed.