aux fuel pump question

[coyote62ny]

i have a mep-003 when in the prime aux run position on the master switch should the auxillary fuel pump run when the fuel tank is full as i understand how this system works is that the float switch does not control the pump but controls the silonoid valve on the auxillary fuel pump to allow fuel to pass to the tank. on my mep-003 the auxillary fuel pump runs with the tank full when in the prime auxillary run position is this normal thanks in advance for your help.

 

[ETN550]

i have a mep-003 when in the prime aux run position on the master switch should the auxillary fuel pump run when the fuel tank is full as i understand how this system works is that the float switch does not control the pump but controls the silonoid valve on the auxillary fuel pump to allow fuel to pass to the tank. on my mep-003 the auxillary fuel pump runs with the tank full when in the prime auxillary run position is this normal thanks in advance for your help.

I have 016Bs but visually the pumps look the same. The 016B does cycle the pump to fill the tank. However, the pump test is to deadhead the pump and measure the pump output pressure. When this is done the pump stops cycling when pressure, about 7 psi, is made. I would conclude that your pump should stop if the solenoid blocks the fuel flow and the power remains connected to the pump. The pump is a positive displacement device so there must be a leak in the pump plunger check valve or there is dirt or rust holding the check open (failed inlet screen) or a scored plunger or the solenoid is not blocking 100%. But if the solenoid was not blocking then the tank would overflow eventually. If it pumped no fuel with the solenoid open and ran with the solenoid blocking then I would say the inlet screen on the pump is clogged with debris. The bottom lid on the pump unscrews by hand to reveal the plastic screen basket for cleaning. Just some ideas.. Someone with a 003 needs to confirm.

Doug

 

[coyote62ny]

i have never hooked the pump up to a fuel supply just noticed it ran when in the prime aux run position i was woundering if this was normal

 

[Keith_J]

If you disconnect the tank switch (remove Cannon plug) on the 002/003A, the solenoid valve on the third pump should not open, meaning no flow. If the pump has no connection/fuel, the air may allow pump cycling. Jumping connections on the Cannon plug will allow flow.

Flow is fast enough to view from the cap. Be careful.

 

[ETN550]

If you disconnect the tank switch (remove Cannon plug) on the 002/003A, the solenoid valve on the third pump should not open, meaning no flow. If the pump has no connection/fuel, the air may allow pump cycling. Jumping connections on the Cannon plug will allow flow.

Flow is fast enough to view from the cap. Be careful.

What ever the situation the pump should probably not run dry for any length of time, especially if there is loud hammering noise. The clicking noise when running with fuel is the check valves working. The fuel adds resistance and provides lubrication and cooling. I only run the pump in aux when it has fuel hooked to it. Passing through aux on the switch is probably designed to provide a few cycles on the pump plunger every time the gen is used to prevent sticking or seizing when fuel is not present. Constant running dry is not good. JMO.

 

[coyote62ny]

thanks for all the help i will put a hose on the aux pump and see if it will pump fuel

 

[Keith_J]

Terminal 17 on S1 is what powers both the pump and the fuel solenoid valve. Terminal 17 is only energized in the AUX position (12:00 position) but since it must be passed every time the set is started, the pump gets exercised.

These pumps have a suction stroke powered by a coil acting on a magnet, then spring force creates the pressure. When the piston reaches the end of the compression stroke (fully up as installed), a switch closes which causes the piston to move in the suction direction (fully down).

These pumps can be overhauled. Remove the pump from the set, then unscrew the bottom. Remove strainer element, then while pressing on the center brass portion, remove the spring clip. The bottom check valve, o-ring, washer and drive spring can now be removed. Remove the piston and clean. Make sure both check valves seal, reassemble with new Viton o-ring and it should work.

If it won't click, it isn't possible to repair.